Atrial fibrillation
Encyclopedia
Atrial fibrillation is the most common cardiac arrhythmia (abnormal heart rhythm). It is a common cause of irregular heart beat, identified clinically by taking a pulse
. Chaotic electrical activity in the two upper chambers (atria
) of the heart
result in the muscle fibrillating (i.e., quivering), instead of achieving coordinated contraction. The presence of AF can be confirmed with an electrocardiogram
(ECG or EKG) by the absence of P waves
and an irregular ventricular rate. Presence of AF in a population increases with age, with 8% of people over 80 having AF.
In AF, the normal electrical impulses that are generated by the sinoatrial node
are suddenly or gradually overwhelmed by disorganized electrical impulses that often originate in the roots of the pulmonary veins, leading to irregular conduction of impulses to the ventricles
which generate the heartbeat. AF may occur in episodes lasting from minutes to weeks, or be permanent in nature. The natural tendency of AF over time is to become a chronic condition. Chronic AF leads to a small increase in the risk of death.
Some people are asymptomatic
despite having frequent episodes, while others experience symptoms that are troubling or incapacitating. Whilst AF is not immediately life-threatening, it may result in palpitations, fainting, chest pain, or congestive heart failure
. People with AF have an increased risk of stroke
because blood tends to form clots in the poorly contracting atria - especially in the left atrial appendage (LAA). The degree of stroke risk can be up to seven times that of the average population, depending on the presence of additional risk factors. In the absence of other risk factors, the risk of stroke in AF patients is similar to that of the general population.
Atrial fibrillation may be treated with medications to either slow the heart rate or revert the heart rhythm back to normal. Synchronized electrical cardioversion
can be used to convert AF to a normal heart rhythm. Surgical and catheter-based therapies may be used to prevent recurrence of AF in certain individuals. People with AF often take anticoagulants such as warfarin
to protect them from stroke.
The American College of Cardiology
(ACC), American Heart Association
(AHA), and the European Society of Cardiology
(ESC) recommend in their guidelines the following classification system based on simplicity and clinical relevance.
All atrial fibrillation patients are initially in the category called first detected AF. These patients may or may not have had previous undetected episodes. If a first detected episode self-terminates in less than 7 days and then another episode begins later on, the case has moved into the category of paroxysmal AF. Although patients in this category have episodes lasting up to 7 days, in most cases of paroxysmal AF the episodes will self-terminate in less than 24 hours. If instead the episode lasts for more than 7 days, it is unlikely to self-terminate, and it is called persistent AF. In this case, the episode may be still terminated by cardioversion. If cardioversion is unsuccessful or it is not attempted, and the episode is ongoing for a long time (e.g. a year or more), the patient's AF is called permanent.
Episodes that last less than 30 seconds are not considered in this classification system. Also, this system does not apply to cases where the AF is a secondary condition that occurs in the setting of a primary condition that may be the cause of the AF.
Using this classification system, it's not always clear what an AF case should be called. For example, a case may fit into the paroxysmal AF category some of the time, while other times it may have the characteristics of persistent AF. One may be able to decide which category is more appropriate by determining which one occurs most often in the case under consideration.
In addition to the above four AF categories, which are mainly defined by episode timing and termination, the ACC/AHA/ESC guidelines describe additional AF categories in terms of other characteristics of the patient.
, and occasionally produce angina (if the rate is faster and puts the heart under strain) and congestive symptoms of shortness of breath or edema
. Sometimes the arrhythmia will be identified only with the onset of a stroke or a transient ischemic attack
(TIA). It is not uncommon for a patient to first become aware of AF from a routine physical examination or ECG
, as it may be asymptomatic in many cases.
As most cases of atrial fibrillation are secondary to other medical problems, the presence of chest pain
or angina
, symptoms of hyperthyroidism
(an overactive thyroid gland) such as weight loss
and diarrhea
, and symptoms suggestive of lung disease would indicate an underlying cause. A history of stroke or TIA, as well as hypertension
(high blood pressure), diabetes
, heart failure and rheumatic fever
, may indicate whether someone with AF is at a higher risk of complications.
), and in some cases may actually be asymptomatic. The patient may complain of palpitations or chest discomfort. The rapid heart rate may result in the heart being unable to provide adequate blood flow and oxygen delivery to the rest of the body. Therefore, common symptoms may include shortness of breath which often worsens with exertion (dyspnea on exertion), shortness of breath when lying flat (orthopnea), and sudden onset of shortness of breath during the night (paroxysmal nocturnal dyspnea), and may progress to swelling of the lower extremities (peripheral edema
). Owing to inadequate blood flow, patients may also complain of light-headedness, may feel like they are about to faint (presyncope
), or may actually lose consciousness (syncope
).
The patient may be in significant respiratory distress
. Because of inadequate oxygen delivery, the patient may appear blue (cyanosis
). By definition, the heart rate will be greater than 100 beats per minute. Blood pressure will be variable, and often difficult to measure as the beat-by-beat variability causes problems for most digital (oscillometric) non-invasive blood pressure
monitors. It is most concerning if consistently lower than usual (hypotension
). Respiratory rate will be increased in the presence of respiratory distress. Pulse oximetry may confirm the presence of hypoxia
related to any precipitating factors such as pneumonia
.
Examination of the jugular veins may reveal elevated pressure
(jugular venous distention).
Lung exam may reveal rales
or crackles, which are suggestive of pulmonary edema
. Heart exam will reveal an irregular but rapid rhythm.
of the arrhythmia, and classification of the arrhythmia. The minimal evaluation of atrial fibrillation is a history and physical examination, ECG, transthoracic echocardiogram, and case specific bloodwork. Depending upon given resources, afflicted individuals may benefit from an in-depth evaluation which may include correlation of the heart rate response to exercise, exercise stress testing, chest X-ray, trans-esophageal echocardiography, and other studies.
If a patient presents with a sudden onset of severe symptoms other forms of tachyarrhythmia must be ruled-out, as some may be immediately life threatening, such as ventricular tachycardia
. While most patients will be placed on continuous cardiorespiratory monitoring, an electrocardiogram
is essential for diagnosis.
Provoking causes should be sought out. A common cause of any tachycardia is dehydration
, as well as other forms of hypovolemia
. Acute coronary syndrome
should be ruled out. Intercurrent illness such as pneumonia
may be present.
for atrial fibrillation is not generally performed, although a study of routine pulse checks or ECGs during routine office visits found that the annual rate of detection of AF in elderly patients improved from 1.04% to 1.63%; selection of patients for prophylactic anticoagulation would improve stroke risk in that age category.
This estimated sensitivity of the routine primary care visit is 64%. This low result probably reflects the pulse not being checked routinely or carefully.
When ECGs are used for screening, the SAFE trial found that electronic software, primary care physician
s and the combination of the two had the following sensitivities and specificities:
and electrolyte
s are routinely determined, as well as thyroid-stimulating hormone
(commonly suppressed in hyperthyroidism
and of relevance if amiodarone
is administered for treatment) and a blood count
.
In acute-onset AF associated with chest pain
, cardiac troponins
or other markers of damage to the heart muscle may be ordered. Coagulation
studies (INR/aPTT) are usually performed, as anticoagulant
medication may be commenced.
QRS complex
es should be narrow, signifying that they are initiated by normal conduction of atrial electrical activity through the intraventricular conduction system
. Wide QRS complexes are worrisome for ventricular tachycardia
, although in cases where there is disease of the conduction system, wide complexes may be present in A-Fib with rapid ventricular response.
If paroxysmal AF is suspected but an ECG during an office visit only shows a regular rhythm, AF episodes may be detected and documented with the use of ambulatory Holter monitor
ing (e.g. for a day). If the episodes are too infrequent to be detected by Holter monitoring with reasonable probability, then the patient can be monitored for longer periods (e.g. a month) with an ambulatory event monitor
.
(which may greatly increase the risk of stroke), left and right atrial size (which indicates likelihood that AF may become permanent), left ventricular size and function, peak right ventricular pressure (pulmonary hypertension
), presence of left atrial thrombus (low sensivity), presence of left ventricular hypertrophy and pericardial disease.
Significant enlargement of both the left and right atria is associated with long-standing atrial fibrillation and, if noted at the initial presentation of atrial fibrillation, suggests that the atrial fibrillation is likely to be of a longer duration than the individual's symptoms.
is generally only performed if a pulmonary cause of atrial fibrillation is suggested, or if other cardiac conditions are suspected (particularly congestive heart failure
.) This may reveal an underlying problem in the lungs or the blood vessels in the chest. In particular, if an underlying pneumonia is suggested, then treatment of the pneumonia may cause the atrial fibrillation to terminate on its own.
(blood clots) in the heart. If this is suspected - e.g. when planning urgent electrical cardioversion - a transesophageal echocardiogram (TEE or TOE where British spelling is used) is preferred.
The TEE has much better visualization of the left atrial appendage than transthoracic echocardiography. This structure, located in the left atrium
, is the place where thrombus is formed in more than 90% of cases in non-valvular (or non-rheumatic) atrial fibrillation or flutter
. TEE has a high sensitivity for locating thrombi in this area and can also detect sluggish bloodflow in this area that is suggestive of thrombus formation.
If no thrombus is seen on TEE, the incidence of stroke, (immediately after cardioversion is performed), is very low.
is a wearable ambulatory heart monitor that continuously monitors the heart rate and heart rhythm for a short duration, typically 24 hours. In individuals with symptoms of significant shortness of breath with exertion or palpitations on a regular basis, a holter monitor may be of benefit to determine if rapid heart rates (or unusually slow heart rates) during atrial fibrillation are the cause of the symptoms.
will evaluate the individual's heart rate response to exertion and determine if the AV node blocking agents are contributing to the symptoms.
Dilation of the atria can be due to almost any structural abnormality of the heart that can cause a rise in the intra-cardiac pressures. This includes valvular heart disease (such as mitral stenosis, mitral regurgitation, and tricuspid regurgitation), hypertension, and congestive heart failure. Any inflammatory state that affects the heart can cause fibrosis of the atria. This is typically due to sarcoidosis but may also be due to autoimmune disorders that create autoantibodies against myosin heavy chains. Mutation of the lamin
AC gene is also associated with fibrosis of the atria that can lead to atrial fibrillation.
Once dilation of the atria has occurred, this begins a chain of events that leads to the activation of the renin aldosterone angiotensin system
(RAAS) and subsequent increase in matrix metaloproteinases and disintegrin, which leads to atrial remodeling and fibrosis, with loss of atrial muscle mass. This process is not immediate, and experimental studies have revealed patchy atrial fibrosis may precede the occurrence of atrial fibrillation and may progress with prolonged durations of atrial fibrillation.
Fibrosis is not limited to the muscle mass of the atria, and may occur in the sinus node (SA node) and atrioventricular node
(AV node), correlating with sick sinus syndrome
. Prolonged episodes of atrial fibrillation have been shown to correlate with prolongation of the sinus node recovery time, suggesting that dysfunction of the SA node is progressive with prolonged episodes of atrial fibrillation.
The normal electrical conduction system of the heart
allows the impulse that is generated by the sinoatrial node
(SA node) of the heart to be propagated to and stimulate the myocardium (muscle of the heart). When the myocardium is stimulated, it contracts. It is the ordered stimulation of the myocardium that allows efficient contraction of the heart, thereby allowing blood to be pumped to the body.
There are multiple theories about the etiology of atrial fibrillation. An important theory is that in atrial fibrillation, the regular impulses produced by the sinus node for a normal heartbeat, are overwhelmed by rapid electrical discharges produced in the atria and adjacent parts of the pulmonary veins. Sources of these disturbances are either automatic foci, often localized at one of the pulmonary veins, or a small number of reentrant sources (rotors) harbored by the posterior wall of the left atrium near the junctions with the pulmonary veins. The pathology progresses from paroxysmal to persistent AF as the sources multiply and localize anywhere in the atria. Because recovery of the atria from excitation is heterogeneous, the electrical waves generated by the AF sources undergo repetitive, spatially distributed breakup and fragmentation in a process known as "fibrillatory conduction".
Another theory is the multiple wavelet
theory first formulated by Moe, which was experimentally proven by Allessie et al.
AF can be distinguished from atrial flutter
(AFL), which appears as an organized electrical circuit usually in the right atrium. AFL produces characteristic saw-toothed F-waves of constant amplitude and frequency on an ECG
whereas AF does not. In AFL, the discharges circulate rapidly at a rate of 300 beats per minute (bpm) around the atrium. In AF, there is no regularity of this kind, except at the sources where the local activation rate can exceed 500 bpm.
Although the electrical impulses of AF occur at a high rate, most of them do not result in a heart beat. A heart beat results when an electrical impulse from the atria passes through the atrioventricular (AV) node
to the ventricles and causes them to contract. During AF, if all of the impulses from the atria passed through the AV node, there would be severe ventricular tachycardia
resulting in severe reduction of cardiac output
. This dangerous situation is prevented by the AV node since its limited conduction velocity reduces the rate at which impulses reach the ventricles during AF.
. Rate or rhythm control are used to achieve the former, while anticoagulation is used to decrease the risk of the latter. If cardiovascularly unstable due to uncontrolled tachycardia
, immediate cardioversion is indicated.
, heparin
, warfarin
, and dabigatran
. Which method is used depends on a number issues including: cost, risk of stroke, risk of falls, compliance, and speed of desired onset of anticoagulation.
There are two ways to approach these symptoms using drugs: rate control and rhythm control. Rate control lowers the heart rate closer to normal, usually 60 to 100 bpm, without trying to convert to a regular rhythm. Rhythm control restores normal heart rhythm in a process called cardioversion and maintains the normal rhythm with drugs. Studies suggest that rhythm control is most important in the acute setting AF, while rate control is more important in the chronic phase. As far as mortality is concerned, the AFFIRM trial showed that there is lower mortality using rate control with anticoagulation treatment versus rhythm control treatment and the difference increases up to 5 years (end of study).
The AFFIRM study also showed no difference in risk of stroke in patients who have converted to a normal rhythm with anti-arrhythmic treatment, compared to those who have only rate control. AF is associated with a reduced quality of life, and while some studies indicate that rhythm control leads to a higher quality of life, the AFFIRM study did not find a difference.
A further study focused on rhythm control in patients with AF with concomitant heart failure, based on the hypothesis that AF confers a higher mortality risk in heart failure. In this setting, rhythm control offered no advantage compared to rate control. However, the diagnosis and progression of atrial fibrillation and other cardiovascular disease requires further investigation.
In patients with a fast ventricular response, intravenous magnesium
significantly increases the chances of successful rate and rhythm control in the urgent setting without major side-effects. A patient with fluctuating vital signs, mental status changes, preexcitation, or chest pain often will go to immediate treatment with synchronized DC cardioversion. Otherwise the decision of rate control versus rhythm control using drugs is made. This is based on a number of criteria that includes whether or not symptoms persist with rate control.
In addition to these agents, amiodarone has some AV node blocking effects (particularly when administered intravenously), and can be used in individuals when other agents are contraindicated or ineffective (particularly due to hypotension).
Diltiazem has been shown to be more effective than either digoxin or amiodarone.
is a noninvasive conversion of an irregular heartbeat to a normal heartbeat using electrical or chemical means:
Vernakalant
has been found to safely and rapidly convert new onset atrial fibrillation.
may be attempted.
formation (blood clotting
). If the clot becomes mobile and is carried away by the blood circulation, it is called an embolus
. An embolus proceeds through smaller and smaller arteries
until it plugs one of them and prevents blood from flowing through the artery. This process results in end-organ damage due to loss of nutrients, oxygen, and removal of cellular waste products. Thrombus can form anywhere in the body, while emboli follow the blood circulation to specific points in the body. Emboli in the brain may results in a ischemic stroke or transient ischemic attack
(TIA).
More than 90% of cases of thrombi associated with non-valvular atrial fibrillation evolve in the left atrial appendage. However, the LAA lies in close relation to the free wall of the left ventricle and thus the LAA's emptying and filling, which determines its degree of blood stagnation, may be helped by the motion of the wall of the left ventricle, if there is good ventricular function.
If the LA is enlarged, there is an increased risk of thrombi that originate in the LA. Moderate to severe, non-rheumatic
, mitral regurgitation
(MR) reduces this risk of stroke. This risk reduction may be due to a beneficial stirring effect of the MR blood flow into the LA.
. The somewhat circular perimeter of the mitral valve is defined by the mitral annulus.
With a normal sinus rhythm, the mitral annulus undergoes dynamic changes during the cardiac cycle
. For example, at the end of diastole
the annular area is smaller than at the end of systole
. A possible reason for this dynamic size difference is that the coordinated contraction of the left atrium
acts like a sphincter
about the mitral annulus and reduces its size. This may be important for mitral valve competence so that it does not leak when the left ventricle pumps blood. However, when the left atrium fibrillates, this sphincter action is not possible and may contribute to, or result in, mitral regurgitation in some cases.
The incidence of atrial fibrillation increases with age. The prevalence in individuals over the age of 80 is about 8%. In developed countries, the number of patients with atrial fibrillation is likely to increase during the next 50 years, owing to the growing proportion of elderly individuals.
made note of dilated, irritated atria in people with mitral stenosis
. The irregular pulse associated with AF was first recorded in 1876 by Carl Wilhelm Hermann Nothnagel
and termed "delirium cordis", stating that "[I]n this form of arrhythmia the heartbeats follow each other in complete irregularity. At the same time, the height and tension of the individual pulse waves are continuously changing". Correlation of delirium cordis with the loss of atrial contraction as reflected in the loss of a waves in the jugular venous pulse
was made by Sir James MacKenzie in 1904. Willem Einthoven
published the first ECG showing AF in 1906. The connection between the anatomic and electrical manifestations of AF and the irregular pulse of delirium cordis was made in 1909 by Carl Julius Rothberger, Heinrich Winterberg, and Sir Thomas Lewis.
Pulse
In medicine, one's pulse represents the tactile arterial palpation of the heartbeat by trained fingertips. The pulse may be palpated in any place that allows an artery to be compressed against a bone, such as at the neck , at the wrist , behind the knee , on the inside of the elbow , and near the...
. Chaotic electrical activity in the two upper chambers (atria
Atrium (anatomy)
In anatomy, the atrium , sometimes called auricle , refers to a chamber or space. For example, the term is used for a portion of the lateral ventricle in the brain and the blood collection chamber of the heart...
) of the heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
result in the muscle fibrillating (i.e., quivering), instead of achieving coordinated contraction. The presence of AF can be confirmed with an electrocardiogram
Electrocardiogram
Electrocardiography is a transthoracic interpretation of the electrical activity of the heart over a period of time, as detected by electrodes attached to the outer surface of the skin and recorded by a device external to the body...
(ECG or EKG) by the absence of P waves
P wave (electrocardiography)
In electrocardiography, during normal atrial depolarization, the main electrical vector is directed from the SA node towards the AV node, and spreads from the right atrium to the left atrium...
and an irregular ventricular rate. Presence of AF in a population increases with age, with 8% of people over 80 having AF.
In AF, the normal electrical impulses that are generated by the sinoatrial node
Sinoatrial node
The sinoatrial node is the impulse-generating tissue located in the right atrium of the heart, and thus the generator of normal sinus rhythm. It is a group of cells positioned on the wall of the right atrium, near the entrance of the superior vena cava...
are suddenly or gradually overwhelmed by disorganized electrical impulses that often originate in the roots of the pulmonary veins, leading to irregular conduction of impulses to the ventricles
Ventricle (heart)
In the heart, a ventricle is one of two large chambers that collect and expel blood received from an atrium towards the peripheral beds within the body and lungs. The Atria primes the Pump...
which generate the heartbeat. AF may occur in episodes lasting from minutes to weeks, or be permanent in nature. The natural tendency of AF over time is to become a chronic condition. Chronic AF leads to a small increase in the risk of death.
Some people are asymptomatic
Asymptomatic
In medicine, a disease is considered asymptomatic if a patient is a carrier for a disease or infection but experiences no symptoms. A condition might be asymptomatic if it fails to show the noticeable symptoms with which it is usually associated. Asymptomatic infections are also called subclinical...
despite having frequent episodes, while others experience symptoms that are troubling or incapacitating. Whilst AF is not immediately life-threatening, it may result in palpitations, fainting, chest pain, or congestive heart failure
Congestive heart failure
Heart failure often called congestive heart failure is generally defined as the inability of the heart to supply sufficient blood flow to meet the needs of the body. Heart failure can cause a number of symptoms including shortness of breath, leg swelling, and exercise intolerance. The condition...
. People with AF have an increased risk of stroke
Stroke
A stroke, previously known medically as a cerebrovascular accident , is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by blockage , or a hemorrhage...
because blood tends to form clots in the poorly contracting atria - especially in the left atrial appendage (LAA). The degree of stroke risk can be up to seven times that of the average population, depending on the presence of additional risk factors. In the absence of other risk factors, the risk of stroke in AF patients is similar to that of the general population.
Atrial fibrillation may be treated with medications to either slow the heart rate or revert the heart rhythm back to normal. Synchronized electrical cardioversion
Cardioversion
Cardioversion is a medical procedure by which an abnormally fast heart rate or cardiac arrhythmia is converted to a normal rhythm, using electricity or drugs. Synchronized electrical cardioversion uses a therapeutic dose of electric current to the heart, at a specific moment in the cardiac cycle...
can be used to convert AF to a normal heart rhythm. Surgical and catheter-based therapies may be used to prevent recurrence of AF in certain individuals. People with AF often take anticoagulants such as warfarin
Warfarin
Warfarin is an anticoagulant. It is most likely to be the drug popularly referred to as a "blood thinner," yet this is a misnomer, since it does not affect the thickness or viscosity of blood...
to protect them from stroke.
Classification
| AF Category | Defining Characteristics |
|---|---|
| First detected | only one diagnosed episode |
| Paroxysmal | recurrent episodes that self-terminate in less than 7 days. |
| Persistent | recurrent episodes that last more than 7 days |
| Permanent | an ongoing long-term episode |
The American College of Cardiology
American College of Cardiology
The American College of Cardiology is a nonprofit medical association established in 1949 to advocate for quality cardiovascular care through education, research promotion, development and application of standards and guidelines, and to influence health care policy...
(ACC), American Heart Association
American Heart Association
The American Heart Association is a non-profit organization in the United States that fosters appropriate cardiac care in an effort to reduce disability and deaths caused by cardiovascular disease and stroke. It is headquartered in Dallas, Texas...
(AHA), and the European Society of Cardiology
European Society of Cardiology
The European Society of Cardiology is a membership organisation of more than 70,000 cardiology professionals across Europe and the Mediterranean. It is involved in scientific and educational activities for cardiology professionals and also promotes cardiovascular disease prevention messages to the...
(ESC) recommend in their guidelines the following classification system based on simplicity and clinical relevance.
All atrial fibrillation patients are initially in the category called first detected AF. These patients may or may not have had previous undetected episodes. If a first detected episode self-terminates in less than 7 days and then another episode begins later on, the case has moved into the category of paroxysmal AF. Although patients in this category have episodes lasting up to 7 days, in most cases of paroxysmal AF the episodes will self-terminate in less than 24 hours. If instead the episode lasts for more than 7 days, it is unlikely to self-terminate, and it is called persistent AF. In this case, the episode may be still terminated by cardioversion. If cardioversion is unsuccessful or it is not attempted, and the episode is ongoing for a long time (e.g. a year or more), the patient's AF is called permanent.
Episodes that last less than 30 seconds are not considered in this classification system. Also, this system does not apply to cases where the AF is a secondary condition that occurs in the setting of a primary condition that may be the cause of the AF.
Using this classification system, it's not always clear what an AF case should be called. For example, a case may fit into the paroxysmal AF category some of the time, while other times it may have the characteristics of persistent AF. One may be able to decide which category is more appropriate by determining which one occurs most often in the case under consideration.
In addition to the above four AF categories, which are mainly defined by episode timing and termination, the ACC/AHA/ESC guidelines describe additional AF categories in terms of other characteristics of the patient.
- Lone atrial fibrillation (LAF) - absence of clinical or echocardiographic findings of other cardiovascular diseaseCardiovascular diseaseHeart disease or cardiovascular disease are the class of diseases that involve the heart or blood vessels . While the term technically refers to any disease that affects the cardiovascular system , it is usually used to refer to those related to atherosclerosis...
(including hypertensionHypertensionHypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. What that means is that the heart is having to work harder than it should to pump the blood around the body. Blood pressure involves two measurements, systolic and...
), related pulmonary disease, or cardiac abnormalities such as enlargement of the left atrium, and age under 60 years - Nonvalvular AF - absence of rheumatic mitral valve disease, a prosthetic heart valve, or mitral valve repairMitral valve repairMitral valve repair is a cardiac surgery procedure performed by cardiac surgeons to treat stenosis or regurgitation of the mitral valve. The mitral valve is the "inflow valve" for the left side of the heart. Blood flows from the lungs, where it picks up oxygen, through the pulmonary veins, to the...
- Secondary AF - occurs in the setting of a primary condition which may be the cause of the AF, such as acute myocardial infarction, cardiac surgeryCardiac surgeryCardiovascular surgery is surgery on the heart or great vessels performed by cardiac surgeons. Frequently, it is done to treat complications of ischemic heart disease , correct congenital heart disease, or treat valvular heart disease from various causes including endocarditis, rheumatic heart...
, pericarditisPericarditisPericarditis is an inflammation of the pericardium . A characteristic chest pain is often present.The causes of pericarditis are varied, including viral infections of the pericardium, idiopathic causes, uremic pericarditis, bacterial infections of the precardium Pericarditis is an inflammation of...
, myocarditisMyocarditisMyocarditis is inflammation of heart muscle . It resembles a heart attack but coronary arteries are not blocked.Myocarditis is most often due to infection by common viruses, such as parvovirus B19, less commonly non-viral pathogens such as Borrelia burgdorferi or Trypanosoma cruzi, or as a...
, hyperthyroidismHyperthyroidismHyperthyroidism is the term for overactive tissue within the thyroid gland causing an overproduction of thyroid hormones . Hyperthyroidism is thus a cause of thyrotoxicosis, the clinical condition of increased thyroid hormones in the blood. Hyperthyroidism and thyrotoxicosis are not synonymous...
, pulmonary embolismPulmonary embolismPulmonary embolism is a blockage of the main artery of the lung or one of its branches by a substance that has travelled from elsewhere in the body through the bloodstream . Usually this is due to embolism of a thrombus from the deep veins in the legs, a process termed venous thromboembolism...
, pneumoniaPneumoniaPneumonia is an inflammatory condition of the lung—especially affecting the microscopic air sacs —associated with fever, chest symptoms, and a lack of air space on a chest X-ray. Pneumonia is typically caused by an infection but there are a number of other causes...
, or other acute pulmonary disease
Signs and symptoms
Atrial fibrillation is usually accompanied by symptoms related to a rapid heart rate. Rapid and irregular heart rates may be perceived as palpitations, exercise intoleranceExercise intolerance
Exercise intolerance is a condition where the patient is unable to do physical exercise at the level or for the duration that would be expected of someone in his or her general physical condition, or experiences unusually severe post-exercise pain, fatigue, or other negative effects...
, and occasionally produce angina (if the rate is faster and puts the heart under strain) and congestive symptoms of shortness of breath or edema
Edema
Edema or oedema ; both words from the Greek , oídēma "swelling"), formerly known as dropsy or hydropsy, is an abnormal accumulation of fluid beneath the skin or in one or more cavities of the body that produces swelling...
. Sometimes the arrhythmia will be identified only with the onset of a stroke or a transient ischemic attack
Transient ischemic attack
A transient ischemic attack is a transient episode of neurologic dysfunction caused by ischemia – either focal brain, spinal cord or retinal – without acute infarction...
(TIA). It is not uncommon for a patient to first become aware of AF from a routine physical examination or ECG
Electrocardiogram
Electrocardiography is a transthoracic interpretation of the electrical activity of the heart over a period of time, as detected by electrodes attached to the outer surface of the skin and recorded by a device external to the body...
, as it may be asymptomatic in many cases.
As most cases of atrial fibrillation are secondary to other medical problems, the presence of chest pain
Chest pain
Chest pain may be a symptom of a number of serious conditions and is generally considered a medical emergency. Even though it may be determined that the pain is non-cardiac in origin, this is often a diagnosis of exclusion made after ruling out more serious causes of the pain.-Differential...
or angina
Angina
Angina pectoris, commonly known as angina, is chest pain due to ischemia of the heart muscle, generally due to obstruction or spasm of the coronary arteries . Coronary artery disease, the main cause of angina, is due to atherosclerosis of the cardiac arteries...
, symptoms of hyperthyroidism
Hyperthyroidism
Hyperthyroidism is the term for overactive tissue within the thyroid gland causing an overproduction of thyroid hormones . Hyperthyroidism is thus a cause of thyrotoxicosis, the clinical condition of increased thyroid hormones in the blood. Hyperthyroidism and thyrotoxicosis are not synonymous...
(an overactive thyroid gland) such as weight loss
Weight loss
Weight loss, in the context of medicine, health or physical fitness, is a reduction of the total body mass, due to a mean loss of fluid, body fat or adipose tissue and/or lean mass, namely bone mineral deposits, muscle, tendon and other connective tissue...
and diarrhea
Diarrhea
Diarrhea , also spelled diarrhoea, is the condition of having three or more loose or liquid bowel movements per day. It is a common cause of death in developing countries and the second most common cause of infant deaths worldwide. The loss of fluids through diarrhea can cause dehydration and...
, and symptoms suggestive of lung disease would indicate an underlying cause. A history of stroke or TIA, as well as hypertension
Hypertension
Hypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. What that means is that the heart is having to work harder than it should to pump the blood around the body. Blood pressure involves two measurements, systolic and...
(high blood pressure), diabetes
Diabetes mellitus
Diabetes mellitus, often simply referred to as diabetes, is a group of metabolic diseases in which a person has high blood sugar, either because the body does not produce enough insulin, or because cells do not respond to the insulin that is produced...
, heart failure and rheumatic fever
Rheumatic fever
Rheumatic fever is an inflammatory disease that occurs following a Streptococcus pyogenes infection, such as strep throat or scarlet fever. Believed to be caused by antibody cross-reactivity that can involve the heart, joints, skin, and brain, the illness typically develops two to three weeks after...
, may indicate whether someone with AF is at a higher risk of complications.
Rapid heart rate
Presentation is similar to other forms of rapid heart rate (tachycardiaTachycardia
Tachycardia comes from the Greek words tachys and kardia . Tachycardia typically refers to a heart rate that exceeds the normal range for a resting heart rate...
), and in some cases may actually be asymptomatic. The patient may complain of palpitations or chest discomfort. The rapid heart rate may result in the heart being unable to provide adequate blood flow and oxygen delivery to the rest of the body. Therefore, common symptoms may include shortness of breath which often worsens with exertion (dyspnea on exertion), shortness of breath when lying flat (orthopnea), and sudden onset of shortness of breath during the night (paroxysmal nocturnal dyspnea), and may progress to swelling of the lower extremities (peripheral edema
Peripheral edema
Peripheral edema is the swelling of tissues, usually in the lower limbs, due to the accumulation of fluids.The condition is commonly associated with aging, but can be caused by many other conditions, including congestive heart failure, trauma, alcoholism, altitude sickness, pregnancy,...
). Owing to inadequate blood flow, patients may also complain of light-headedness, may feel like they are about to faint (presyncope
Presyncope
Presyncope is a state consisting of lightheadedness, muscular weakness, and feeling faint . Pre-syncope does not result from primary central nervous system pathology, nor does it originate in the inner ear, but is most often cardiovascular in etiology. In many patients, lightheadedness is a symptom...
), or may actually lose consciousness (syncope
Syncope (medicine)
Syncope , the medical term for fainting, is precisely defined as a transient loss of consciousness and postural tone characterized by rapid onset, short duration, and spontaneous recovery due to global cerebral hypoperfusion that most often results from hypotension.Many forms of syncope are...
).
The patient may be in significant respiratory distress
Respiratory distress
Respiratory distress may refer to either/both:* Labored breathing, the physical presentation of respiratory distress*Shortness of breath or dyspnea - a sensation of respiratory distress-See also:*List of terms of lung size and activity...
. Because of inadequate oxygen delivery, the patient may appear blue (cyanosis
Cyanosis
Cyanosis is the appearance of a blue or purple coloration of the skin or mucous membranes due to the tissues near the skin surface being low on oxygen. The onset of cyanosis is 2.5 g/dL of deoxyhemoglobin. The bluish color is more readily apparent in those with high hemoglobin counts than it is...
). By definition, the heart rate will be greater than 100 beats per minute. Blood pressure will be variable, and often difficult to measure as the beat-by-beat variability causes problems for most digital (oscillometric) non-invasive blood pressure
Sphygmomanometer
A sphygmomanometer or blood pressure meter is a device used to measure blood pressure, comprising an inflatable cuff to restrict blood flow, and a mercury or mechanical manometer to measure the pressure. It is always used in conjunction with a means to determine at what pressure blood flow is just...
monitors. It is most concerning if consistently lower than usual (hypotension
Hypotension
In physiology and medicine, hypotension is abnormally low blood pressure, especially in the arteries of the systemic circulation. It is best understood as a physiologic state, rather than a disease. It is often associated with shock, though not necessarily indicative of it. Hypotension is the...
). Respiratory rate will be increased in the presence of respiratory distress. Pulse oximetry may confirm the presence of hypoxia
Hypoxia (medical)
Hypoxia, or hypoxiation, is a pathological condition in which the body as a whole or a region of the body is deprived of adequate oxygen supply. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise...
related to any precipitating factors such as pneumonia
Pneumonia
Pneumonia is an inflammatory condition of the lung—especially affecting the microscopic air sacs —associated with fever, chest symptoms, and a lack of air space on a chest X-ray. Pneumonia is typically caused by an infection but there are a number of other causes...
.
Examination of the jugular veins may reveal elevated pressure
Jugular venous pressure
The jugular venous pressure is the indirectly observed pressure over the venous system...
(jugular venous distention).
Lung exam may reveal rales
Rales
Crackles, crepitations, or rales are the clicking, rattling, or crackling noises that may be made by one or both lungs of a human with a respiratory disease during inhalation. They are often heard only with a stethoscope...
or crackles, which are suggestive of pulmonary edema
Pulmonary edema
Pulmonary edema , or oedema , is fluid accumulation in the air spaces and parenchyma of the lungs. It leads to impaired gas exchange and may cause respiratory failure...
. Heart exam will reveal an irregular but rapid rhythm.
Association with other conditions
- Central sleep apneaCentral sleep apneaCentral sleep apnea or central sleep apnea syndrome is a sleep-related disorder in which the effort to breathe is diminished or absent, typically for 10 to 30 seconds, either intermittently or in cycles and is usually associated with a reduction in blood oxygen saturation...
(CSA) – A study found that the prevalence of atrial fibrillation among patients with idiopathic central sleep apnea was significantly higher than the prevalence among patients with obstructive sleep apneaObstructive sleep apneaObstructive sleep apnea or obstructive sleep apnea syndrome is the most common type of sleep apnea and is caused by obstruction of the upper airway. It is characterized by repetitive pauses in breathing during sleep, despite the effort to breathe, and is usually associated with a reduction in...
or no sleep apneaSleep apneaSleep apnea is a sleep disorder characterized by abnormal pauses in breathing or instances of abnormally low breathing, during sleep. Each pause in breathing, called an apnea, can last from a few seconds to minutes, and may occur 5 to 30 times or more an hour. Similarly, each abnormally low...
(27%, 1.7%, and 3.3%, respectively). There was a total of 180 subjects with 60 people in each of the 3 groups. Possible explanations for the association between CSA and AF are a causal relationship between the two conditions, or an abnormality of central cardiorespiratory regulation. - Left atrial enlargementLeft atrial enlargementLeft atrial enlargement or left atrial dilation is a form of cardiomegaly.In the general population, obesity appears to be the most important risk factor for LAE. Also, a study found that LAE can occur as a consequence of atrial fibrillation , although another study found that AF by itself does...
- Mitral stenosisMitral stenosisMitral stenosis is a valvular heart disease characterized by the narrowing of the orifice of the mitral valve of the heart.-Signs and symptoms:Symptoms of mitral stenosis include:...
Diagnosis
The evaluation of atrial fibrillation involves diagnosis, determination of the etiologyEtiology
Etiology is the study of causation, or origination. The word is derived from the Greek , aitiologia, "giving a reason for" ....
of the arrhythmia, and classification of the arrhythmia. The minimal evaluation of atrial fibrillation is a history and physical examination, ECG, transthoracic echocardiogram, and case specific bloodwork. Depending upon given resources, afflicted individuals may benefit from an in-depth evaluation which may include correlation of the heart rate response to exercise, exercise stress testing, chest X-ray, trans-esophageal echocardiography, and other studies.
If a patient presents with a sudden onset of severe symptoms other forms of tachyarrhythmia must be ruled-out, as some may be immediately life threatening, such as ventricular tachycardia
Ventricular tachycardia
Ventricular tachycardia is a tachycardia, or fast heart rhythm, that originates in one of the ventricles of the heart...
. While most patients will be placed on continuous cardiorespiratory monitoring, an electrocardiogram
Electrocardiogram
Electrocardiography is a transthoracic interpretation of the electrical activity of the heart over a period of time, as detected by electrodes attached to the outer surface of the skin and recorded by a device external to the body...
is essential for diagnosis.
Provoking causes should be sought out. A common cause of any tachycardia is dehydration
Dehydration
In physiology and medicine, dehydration is defined as the excessive loss of body fluid. It is literally the removal of water from an object; however, in physiological terms, it entails a deficiency of fluid within an organism...
, as well as other forms of hypovolemia
Hypovolemia
In physiology and medicine, hypovolemia is a state of decreased blood volume; more specifically, decrease in volume of blood plasma...
. Acute coronary syndrome
Acute coronary syndrome
Acute coronary syndrome is usually one of three diseases involving the coronary arteries: ST elevation myocardial infarction , non ST elevation myocardial infarction , or unstable angina ....
should be ruled out. Intercurrent illness such as pneumonia
Pneumonia
Pneumonia is an inflammatory condition of the lung—especially affecting the microscopic air sacs —associated with fever, chest symptoms, and a lack of air space on a chest X-ray. Pneumonia is typically caused by an infection but there are a number of other causes...
may be present.
Screening
ScreeningScreening (medicine)
Screening, in medicine, is a strategy used in a population to detect a disease in individuals without signs or symptoms of that disease. Unlike what generally happens in medicine, screening tests are performed on persons without any clinical sign of disease....
for atrial fibrillation is not generally performed, although a study of routine pulse checks or ECGs during routine office visits found that the annual rate of detection of AF in elderly patients improved from 1.04% to 1.63%; selection of patients for prophylactic anticoagulation would improve stroke risk in that age category.
This estimated sensitivity of the routine primary care visit is 64%. This low result probably reflects the pulse not being checked routinely or carefully.
When ECGs are used for screening, the SAFE trial found that electronic software, primary care physician
Primary care physician
A primary care physician, or PCP, is a physician/medical doctor who provides both the first contact for a person with an undiagnosed health concern as well as continuing care of varied medical conditions, not limited by cause, organ system, or diagnosis....
s and the combination of the two had the following sensitivities and specificities:
- Interpreted by software: sensitivity = 83%, specificity = 99%
- Interpreted by a primary care physician: sensitivity = 80%, specificity = 92%
- Interpreted by a primary care physician with software: sensitivity = 92%, specificity = 91%
Minimal evaluation
The minimal evaluation of atrial fibrillation should generally be performed in all individuals with AF. The goal of this evaluation is to determine the general treatment regimen for the individual. If results of the general evaluation warrant it, further studies may then be performed.History and physical examination
The history of the individual's atrial fibrillation episodes is probably the most important part of the evaluation. Distinctions should be made between those who are entirely asymptomatic when they are in AF (in which case the AF is found as an incidental finding on an ECG or physical examination) and those who have gross and obvious symptoms due to AF and can pinpoint whenever they go into AF or revert to sinus rhythm.Routine bloodwork
While many cases of AF have no definite cause, it may be the result of various other problems (see below). Hence, renal functionRenal function
Renal function, in nephrology, is an indication of the state of the kidney and its role in renal physiology. Glomerular filtration rate describes the flow rate of filtered fluid through the kidney...
and electrolyte
Electrolyte
In chemistry, an electrolyte is any substance containing free ions that make the substance electrically conductive. The most typical electrolyte is an ionic solution, but molten electrolytes and solid electrolytes are also possible....
s are routinely determined, as well as thyroid-stimulating hormone
Thyroid-stimulating hormone
Thyrotrophin-stimulating hormone is a peptide hormone synthesized and secreted by thyrotrope cells in the anterior pituitary gland, which regulates the endocrine function of the thyroid gland.- Physiology :...
(commonly suppressed in hyperthyroidism
Hyperthyroidism
Hyperthyroidism is the term for overactive tissue within the thyroid gland causing an overproduction of thyroid hormones . Hyperthyroidism is thus a cause of thyrotoxicosis, the clinical condition of increased thyroid hormones in the blood. Hyperthyroidism and thyrotoxicosis are not synonymous...
and of relevance if amiodarone
Amiodarone
Amiodarone is an antiarrhythmic agent used for various types of tachyarrhythmias , both ventricular and supraventricular arrhythmias. Discovered in 1961, it was not approved for use in the United States until 1985...
is administered for treatment) and a blood count
Complete blood count
A complete blood count , also known as full blood count or full blood exam or blood panel, is a test panel requested by a doctor or other medical professional that gives information about the cells in a patient's blood...
.
In acute-onset AF associated with chest pain
Chest pain
Chest pain may be a symptom of a number of serious conditions and is generally considered a medical emergency. Even though it may be determined that the pain is non-cardiac in origin, this is often a diagnosis of exclusion made after ruling out more serious causes of the pain.-Differential...
, cardiac troponins
Troponin
400px|thumb|right|alt = Colored dice with checkered background|Ribbon representation of the human cardiac troponin core complex in the calcium-saturated form...
or other markers of damage to the heart muscle may be ordered. Coagulation
Coagulation
Coagulation is a complex process by which blood forms clots. It is an important part of hemostasis, the cessation of blood loss from a damaged vessel, wherein a damaged blood vessel wall is covered by a platelet and fibrin-containing clot to stop bleeding and begin repair of the damaged vessel...
studies (INR/aPTT) are usually performed, as anticoagulant
Anticoagulant
An anticoagulant is a substance that prevents coagulation of blood. A group of pharmaceuticals called anticoagulants can be used in vivo as a medication for thrombotic disorders. Some anticoagulants are used in medical equipment, such as test tubes, blood transfusion bags, and renal dialysis...
medication may be commenced.
Electrocardiogram
Atrial fibrillation is diagnosed on an electrocardiogram (ECG), an investigation performed routinely whenever an irregular heart beat is suspected. Characteristic findings are the absence of P waves, with unorganized electrical activity in their place, and irregular R-R intervals due to irregular conduction of impulses to the ventricles. However, irregular R-R intervals may be difficult to determine if the rate is extremely rapid.QRS complex
QRS complex
The QRS complex is a name for the combination of three of the graphical deflections seen on a typical electrocardiogram . It is usually the central and most visually obvious part of the tracing. It corresponds to the depolarization of the right and left ventricles of the human heart...
es should be narrow, signifying that they are initiated by normal conduction of atrial electrical activity through the intraventricular conduction system
Electrical conduction system of the heart
The normal intrinsic electrical conduction of the heart allows electrical propagation to be transmitted from the Sinoatrial Node through both atria and forward to the Atrioventricular Node. Normal/baseline physiology allows further propagation from the AV node to the ventricle or Purkinje Fibers...
. Wide QRS complexes are worrisome for ventricular tachycardia
Ventricular tachycardia
Ventricular tachycardia is a tachycardia, or fast heart rhythm, that originates in one of the ventricles of the heart...
, although in cases where there is disease of the conduction system, wide complexes may be present in A-Fib with rapid ventricular response.
If paroxysmal AF is suspected but an ECG during an office visit only shows a regular rhythm, AF episodes may be detected and documented with the use of ambulatory Holter monitor
Holter monitor
In medicine, a Holter monitor is a portable device for continuously monitoring various electrical activity of the cardiovascular system for at least 24 hours...
ing (e.g. for a day). If the episodes are too infrequent to be detected by Holter monitoring with reasonable probability, then the patient can be monitored for longer periods (e.g. a month) with an ambulatory event monitor
Cardiac event monitor
A cardiac event monitor is a device used to monitor patients with transient cardiac symptoms.There are two broad classifications for cardiac event monitors: manual and automatic. Automatic ECG event monitors such have the ability to monitor the patient's ECG and make recordings of abnormal events...
.
Echocardiography
A non-invasive transthoracic echocardiogram (TTE) is generally performed in newly diagnosed AF, as well as if there is a major change in the patient's clinical state. This ultrasound-based scan of the heart may help identify valvular heart diseaseValvular heart disease
Valvular heart disease is any disease process involving one or more of the valves of the heart . Valve problems may be congenital or acquired...
(which may greatly increase the risk of stroke), left and right atrial size (which indicates likelihood that AF may become permanent), left ventricular size and function, peak right ventricular pressure (pulmonary hypertension
Pulmonary hypertension
In medicine, pulmonary hypertension is an increase in blood pressure in the pulmonary artery, pulmonary vein, or pulmonary capillaries, together known as the lung vasculature, leading to shortness of breath, dizziness, fainting, and other symptoms, all of which are exacerbated by exertion...
), presence of left atrial thrombus (low sensivity), presence of left ventricular hypertrophy and pericardial disease.
Significant enlargement of both the left and right atria is associated with long-standing atrial fibrillation and, if noted at the initial presentation of atrial fibrillation, suggests that the atrial fibrillation is likely to be of a longer duration than the individual's symptoms.
Extended evaluation
An extended evaluation is generally not necessary in most individuals with atrial fibrillation, and is only performed if abnormalities are noted in the limited evaluation, if a reversible cause of the atrial fibrillation is suggested, or if further evaluation may change the treatment course.Chest X-ray
A chest X-rayChest X-ray
In medicine, a chest radiograph, commonly called a chest X-ray , is a projection radiograph of the chest used to diagnose conditions affecting the chest, its contents, and nearby structures...
is generally only performed if a pulmonary cause of atrial fibrillation is suggested, or if other cardiac conditions are suspected (particularly congestive heart failure
Congestive heart failure
Heart failure often called congestive heart failure is generally defined as the inability of the heart to supply sufficient blood flow to meet the needs of the body. Heart failure can cause a number of symptoms including shortness of breath, leg swelling, and exercise intolerance. The condition...
.) This may reveal an underlying problem in the lungs or the blood vessels in the chest. In particular, if an underlying pneumonia is suggested, then treatment of the pneumonia may cause the atrial fibrillation to terminate on its own.
Transesophageal echocardiogram
A normal echocardiography (transthoracic or TTE) has a low sensitivity for identifying thrombiThrombus
A thrombus , or blood clot, is the final product of the blood coagulation step in hemostasis. It is achieved via the aggregation of platelets that form a platelet plug, and the activation of the humoral coagulation system...
(blood clots) in the heart. If this is suspected - e.g. when planning urgent electrical cardioversion - a transesophageal echocardiogram (TEE or TOE where British spelling is used) is preferred.
The TEE has much better visualization of the left atrial appendage than transthoracic echocardiography. This structure, located in the left atrium
Left atrium
The left atrium is one of the four chambers in the human heart. It receives oxygenated blood from the pulmonary veins, and pumps it into the left ventricle, via the mitral valve.-Foramen ovale:...
, is the place where thrombus is formed in more than 90% of cases in non-valvular (or non-rheumatic) atrial fibrillation or flutter
Atrial flutter
Atrial flutter is an abnormal heart rhythm that occurs in the atria of the heart. When it first occurs, it is usually associated with a fast heart rate or tachycardia , and falls into the category of supra-ventricular tachycardias. While this rhythm occurs most often in individuals with...
. TEE has a high sensitivity for locating thrombi in this area and can also detect sluggish bloodflow in this area that is suggestive of thrombus formation.
If no thrombus is seen on TEE, the incidence of stroke, (immediately after cardioversion is performed), is very low.
Ambulatory Holter monitoring
A Holter monitorHolter monitor
In medicine, a Holter monitor is a portable device for continuously monitoring various electrical activity of the cardiovascular system for at least 24 hours...
is a wearable ambulatory heart monitor that continuously monitors the heart rate and heart rhythm for a short duration, typically 24 hours. In individuals with symptoms of significant shortness of breath with exertion or palpitations on a regular basis, a holter monitor may be of benefit to determine if rapid heart rates (or unusually slow heart rates) during atrial fibrillation are the cause of the symptoms.
Exercise stress testing
Some individuals with atrial fibrillation do well with normal activity but develop shortness of breath with exertion. It may be unclear if the shortness of breath is due to a blunted heart rate response to exertion caused by excessive AV node blocking agents, a very rapid heart rate during exertion, or due to other underlying conditions such as chronic lung disease or coronary ischemia. An exercise stress testCardiac stress test
Cardiac stress test is a test used in medicine and cardiology to measure the heart's ability to respond to external stress in a controlled clinical environment....
will evaluate the individual's heart rate response to exertion and determine if the AV node blocking agents are contributing to the symptoms.
Cause
AF is linked to several cardiac causes, but may occur in otherwise normal hearts. Known associations include:- HypertensionHypertensionHypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. What that means is that the heart is having to work harder than it should to pump the blood around the body. Blood pressure involves two measurements, systolic and...
(High blood pressure) - Primary heart diseases including coronary artery disease, mitral stenosisMitral stenosisMitral stenosis is a valvular heart disease characterized by the narrowing of the orifice of the mitral valve of the heart.-Signs and symptoms:Symptoms of mitral stenosis include:...
(e.g. due to rheumatic heart disease or mitral valve prolapseMitral valve prolapseMitral valve prolapse is a valvular heart disease characterized by the displacement of an abnormally thickened mitral valve leaflet into the left atrium during systole. There are various types of MVP, broadly classified as classic and nonclassic. In its nonclassic form, MVP carries a low risk of...
), mitral regurgitationMitral regurgitationMitral regurgitation , mitral insufficiency or mitral incompetence is a disorder of the heart in which the mitral valve does not close properly when the heart pumps out blood. It is the abnormal leaking of blood from the left ventricle, through the mitral valve, and into the left atrium, when...
, hypertrophic cardiomyopathyHypertrophic cardiomyopathyHypertrophic cardiomyopathy is a disease of the myocardium in which a portion of the myocardium is hypertrophied without any obvious cause...
(HCM), pericarditisPericarditisPericarditis is an inflammation of the pericardium . A characteristic chest pain is often present.The causes of pericarditis are varied, including viral infections of the pericardium, idiopathic causes, uremic pericarditis, bacterial infections of the precardium Pericarditis is an inflammation of...
, congenital heart disease, previous heart surgery - Lung diseases (such as pneumoniaPneumoniaPneumonia is an inflammatory condition of the lung—especially affecting the microscopic air sacs —associated with fever, chest symptoms, and a lack of air space on a chest X-ray. Pneumonia is typically caused by an infection but there are a number of other causes...
, lung cancerLung cancerLung cancer is a disease characterized by uncontrolled cell growth in tissues of the lung. If left untreated, this growth can spread beyond the lung in a process called metastasis into nearby tissue and, eventually, into other parts of the body. Most cancers that start in lung, known as primary...
, pulmonary embolismPulmonary embolismPulmonary embolism is a blockage of the main artery of the lung or one of its branches by a substance that has travelled from elsewhere in the body through the bloodstream . Usually this is due to embolism of a thrombus from the deep veins in the legs, a process termed venous thromboembolism...
, sarcoidosisSarcoidosisSarcoidosis , also called sarcoid, Besnier-Boeck disease or Besnier-Boeck-Schaumann disease, is a disease in which abnormal collections of chronic inflammatory cells form as nodules in multiple organs. The cause of sarcoidosis is unknown...
) - Excessive alcoholAlcoholic beverageAn alcoholic beverage is a drink containing ethanol, commonly known as alcohol. Alcoholic beverages are divided into three general classes: beers, wines, and spirits. They are legally consumed in most countries, and over 100 countries have laws regulating their production, sale, and consumption...
consumption ("binge drinkingBinge drinkingBinge drinking or heavy episodic drinking is the modern epithet for drinking alcoholic beverages with the primary intention of becoming intoxicated by heavy consumption of alcohol over a short period of time. It is a kind of purposeful drinking style that is popular in several countries worldwide,...
" or "holiday heart syndromeHoliday heart syndromeHoliday heart syndrome is an irregular heartbeat pattern presented in individuals who are otherwise healthy. It can be the result of stress, dehydration, and drinking. Sometimes associated with binge drinking, the condition can also occur when individuals consume only moderate amounts of...
"). Even otherwise healthy middle-aged women who consumed more than 2 drinks daily were 60% more likely to develop AF. - HyperthyroidismHyperthyroidismHyperthyroidism is the term for overactive tissue within the thyroid gland causing an overproduction of thyroid hormones . Hyperthyroidism is thus a cause of thyrotoxicosis, the clinical condition of increased thyroid hormones in the blood. Hyperthyroidism and thyrotoxicosis are not synonymous...
- Carbon monoxide poisoningCarbon monoxide poisoningCarbon monoxide poisoning occurs after enough inhalation of carbon monoxide . Carbon monoxide is a toxic gas, but, being colorless, odorless, tasteless, and initially non-irritating, it is very difficult for people to detect...
- Dual-chamber pacemakerPacemakerAn artificial pacemaker is a medical device that uses electrical impulses to regulate the beating of the heart.Pacemaker may also refer to:-Medicine:...
s in the presence of normal atrioventricular conduction. - A family history of AF may increase the risk of AF. A study of more than 2,200 AF patients found that 30 per cent had parents with AF. Various genetic mutations may be responsible.
- Friedreich's ataxiaFriedreich's ataxiaFriedreich's ataxia is an inherited disease that causes progressive damage to the nervous system, resulting in symptoms ranging from gait disturbance to speech problems; it can also lead to heart disease and diabetes....
Morphology
The primary pathologic change seen in atrial fibrillation is the progressive fibrosis of the atria. This fibrosis is primarily due to atrial dilation, however genetic causes and inflammation may have a cause in some individuals. One study found that atrial dilation can occur as a consequence of AF, although another study found that AF by itself does not cause it.Dilation of the atria can be due to almost any structural abnormality of the heart that can cause a rise in the intra-cardiac pressures. This includes valvular heart disease (such as mitral stenosis, mitral regurgitation, and tricuspid regurgitation), hypertension, and congestive heart failure. Any inflammatory state that affects the heart can cause fibrosis of the atria. This is typically due to sarcoidosis but may also be due to autoimmune disorders that create autoantibodies against myosin heavy chains. Mutation of the lamin
Lamin
Nuclear lamins, also known as Class V intermediate filaments, are fibrous proteins providing structural function and transcriptional regulation in the cell nucleus. Nuclear lamins interact with membrane-associated proteins to form the nuclear lamina on the interior of the nuclear envelope...
AC gene is also associated with fibrosis of the atria that can lead to atrial fibrillation.
Once dilation of the atria has occurred, this begins a chain of events that leads to the activation of the renin aldosterone angiotensin system
Renin-angiotensin system
The renin-angiotensin system or the renin-angiotensin-aldosterone system is a hormone system that regulates blood pressure and water balance....
(RAAS) and subsequent increase in matrix metaloproteinases and disintegrin, which leads to atrial remodeling and fibrosis, with loss of atrial muscle mass. This process is not immediate, and experimental studies have revealed patchy atrial fibrosis may precede the occurrence of atrial fibrillation and may progress with prolonged durations of atrial fibrillation.
Fibrosis is not limited to the muscle mass of the atria, and may occur in the sinus node (SA node) and atrioventricular node
Atrioventricular node
The atrioventricular node is a part of the electrical control system of the heart that coordinates heart rate. It electrically connects atrial and ventricular chambers...
(AV node), correlating with sick sinus syndrome
Sick sinus syndrome
Sick sinus syndrome, also called sinus node dysfunction, is a group of abnormal heart rhythms presumably caused by a malfunction of the sinus node, the heart's primary pacemaker...
. Prolonged episodes of atrial fibrillation have been shown to correlate with prolongation of the sinus node recovery time, suggesting that dysfunction of the SA node is progressive with prolonged episodes of atrial fibrillation.
Electrophysiology
| Conduction | |
| Sinus rhythm | Atrial fibrillation |
The normal electrical conduction system of the heart
Electrical conduction system of the heart
The normal intrinsic electrical conduction of the heart allows electrical propagation to be transmitted from the Sinoatrial Node through both atria and forward to the Atrioventricular Node. Normal/baseline physiology allows further propagation from the AV node to the ventricle or Purkinje Fibers...
allows the impulse that is generated by the sinoatrial node
Sinoatrial node
The sinoatrial node is the impulse-generating tissue located in the right atrium of the heart, and thus the generator of normal sinus rhythm. It is a group of cells positioned on the wall of the right atrium, near the entrance of the superior vena cava...
(SA node) of the heart to be propagated to and stimulate the myocardium (muscle of the heart). When the myocardium is stimulated, it contracts. It is the ordered stimulation of the myocardium that allows efficient contraction of the heart, thereby allowing blood to be pumped to the body.
There are multiple theories about the etiology of atrial fibrillation. An important theory is that in atrial fibrillation, the regular impulses produced by the sinus node for a normal heartbeat, are overwhelmed by rapid electrical discharges produced in the atria and adjacent parts of the pulmonary veins. Sources of these disturbances are either automatic foci, often localized at one of the pulmonary veins, or a small number of reentrant sources (rotors) harbored by the posterior wall of the left atrium near the junctions with the pulmonary veins. The pathology progresses from paroxysmal to persistent AF as the sources multiply and localize anywhere in the atria. Because recovery of the atria from excitation is heterogeneous, the electrical waves generated by the AF sources undergo repetitive, spatially distributed breakup and fragmentation in a process known as "fibrillatory conduction".
Another theory is the multiple wavelet
Wavelet
A wavelet is a wave-like oscillation with an amplitude that starts out at zero, increases, and then decreases back to zero. It can typically be visualized as a "brief oscillation" like one might see recorded by a seismograph or heart monitor. Generally, wavelets are purposefully crafted to have...
theory first formulated by Moe, which was experimentally proven by Allessie et al.
AF can be distinguished from atrial flutter
Atrial flutter
Atrial flutter is an abnormal heart rhythm that occurs in the atria of the heart. When it first occurs, it is usually associated with a fast heart rate or tachycardia , and falls into the category of supra-ventricular tachycardias. While this rhythm occurs most often in individuals with...
(AFL), which appears as an organized electrical circuit usually in the right atrium. AFL produces characteristic saw-toothed F-waves of constant amplitude and frequency on an ECG
Electrocardiogram
Electrocardiography is a transthoracic interpretation of the electrical activity of the heart over a period of time, as detected by electrodes attached to the outer surface of the skin and recorded by a device external to the body...
whereas AF does not. In AFL, the discharges circulate rapidly at a rate of 300 beats per minute (bpm) around the atrium. In AF, there is no regularity of this kind, except at the sources where the local activation rate can exceed 500 bpm.
Although the electrical impulses of AF occur at a high rate, most of them do not result in a heart beat. A heart beat results when an electrical impulse from the atria passes through the atrioventricular (AV) node
Atrioventricular node
The atrioventricular node is a part of the electrical control system of the heart that coordinates heart rate. It electrically connects atrial and ventricular chambers...
to the ventricles and causes them to contract. During AF, if all of the impulses from the atria passed through the AV node, there would be severe ventricular tachycardia
Ventricular tachycardia
Ventricular tachycardia is a tachycardia, or fast heart rhythm, that originates in one of the ventricles of the heart...
resulting in severe reduction of cardiac output
Cardiac output
Cardiac output is the volume of blood being pumped by the heart, in particular by a left or right ventricle in the time interval of one minute. CO may be measured in many ways, for example dm3/min...
. This dangerous situation is prevented by the AV node since its limited conduction velocity reduces the rate at which impulses reach the ventricles during AF.
Management
The main goals of treatment are to prevent circulatory instability and strokeStroke
A stroke, previously known medically as a cerebrovascular accident , is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by blockage , or a hemorrhage...
. Rate or rhythm control are used to achieve the former, while anticoagulation is used to decrease the risk of the latter. If cardiovascularly unstable due to uncontrolled tachycardia
Tachycardia
Tachycardia comes from the Greek words tachys and kardia . Tachycardia typically refers to a heart rate that exceeds the normal range for a resting heart rate...
, immediate cardioversion is indicated.
Anticoagulation
Anticoagulation can be achieved through a number of means including the use of aspirinAspirin
Aspirin , also known as acetylsalicylic acid , is a salicylate drug, often used as an analgesic to relieve minor aches and pains, as an antipyretic to reduce fever, and as an anti-inflammatory medication. It was discovered by Arthur Eichengrun, a chemist with the German company Bayer...
, heparin
Heparin
Heparin , also known as unfractionated heparin, a highly sulfated glycosaminoglycan, is widely used as an injectable anticoagulant, and has the highest negative charge density of any known biological molecule...
, warfarin
Warfarin
Warfarin is an anticoagulant. It is most likely to be the drug popularly referred to as a "blood thinner," yet this is a misnomer, since it does not affect the thickness or viscosity of blood...
, and dabigatran
Dabigatran
Dabigatran is an oral anticoagulant from the class of the direct thrombin inhibitors...
. Which method is used depends on a number issues including: cost, risk of stroke, risk of falls, compliance, and speed of desired onset of anticoagulation.
Rate control versus rhythm control using drugs
AF can cause disabling and bothersome symptoms. Palpitations, chest discomfort, anxiety, and decreased exercise tolerance are related to rapid heart rate and inefficient cardiac output caused by AF. Furthermore, AF with a persistent rapid rate can cause a form of heart failure called tachycardia induced cardiomyopathy. This can significantly increase mortality and morbidity, which can be prevented by early and adequate treatment of the AF.There are two ways to approach these symptoms using drugs: rate control and rhythm control. Rate control lowers the heart rate closer to normal, usually 60 to 100 bpm, without trying to convert to a regular rhythm. Rhythm control restores normal heart rhythm in a process called cardioversion and maintains the normal rhythm with drugs. Studies suggest that rhythm control is most important in the acute setting AF, while rate control is more important in the chronic phase. As far as mortality is concerned, the AFFIRM trial showed that there is lower mortality using rate control with anticoagulation treatment versus rhythm control treatment and the difference increases up to 5 years (end of study).
The AFFIRM study also showed no difference in risk of stroke in patients who have converted to a normal rhythm with anti-arrhythmic treatment, compared to those who have only rate control. AF is associated with a reduced quality of life, and while some studies indicate that rhythm control leads to a higher quality of life, the AFFIRM study did not find a difference.
A further study focused on rhythm control in patients with AF with concomitant heart failure, based on the hypothesis that AF confers a higher mortality risk in heart failure. In this setting, rhythm control offered no advantage compared to rate control. However, the diagnosis and progression of atrial fibrillation and other cardiovascular disease requires further investigation.
In patients with a fast ventricular response, intravenous magnesium
Magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...
significantly increases the chances of successful rate and rhythm control in the urgent setting without major side-effects. A patient with fluctuating vital signs, mental status changes, preexcitation, or chest pain often will go to immediate treatment with synchronized DC cardioversion. Otherwise the decision of rate control versus rhythm control using drugs is made. This is based on a number of criteria that includes whether or not symptoms persist with rate control.
Rate control
Rate control is achieved with medications that work by increasing the degree of block at the level of the AV node, effectively decreasing the number of impulses that conduct into the ventricles. This can be done with:- Beta blockers (preferably the "cardioselective" beta blockers such as metoprololMetoprololMetoprolol is a selective β1 receptor blocker used in treatment of several diseases of the cardiovascular system, especially hypertension. The active substance metoprolol is employed either as metoprolol succinate or metoprolol tartrate...
, atenolol, bisoprololBisoprololBisoprolol is a drug belonging to the group of beta blockers, a class of drugs used primarily in cardiovascular diseases. More specifically, it is a selective type β1 adrenergic receptor blocker. The FDA approved Duramed Pharmaceutical's application for Zebeta Oral Tablets as a new molecular...
, nebivololNebivololNebivolol is a β1 receptor blocker with nitric oxide-potentiating vasodilatory effect used in treatment of hypertension and, in Europe, also for left ventricular failure...
) - Non-dihydropyridine calcium channel blockerCalcium channel blockerA calcium channel blocker is a chemical that disrupts the movement of calcium through calcium channels.CCB drugs devised to target neurons are used as antiepileptics. However, the most widespread clinical usage of calcium channel blockers is to decrease blood pressure in patients with...
s (i.e. diltiazemDiltiazemDiltiazem is a non-dihydropyridine member of the class of drugs known as calcium channel blockers, used in the treatment of hypertension, angina pectoris, and some types of arrhythmia....
or verapamilVerapamilVerapamil is an L-type calcium channel blocker of the phenylalkylamine class. It has been used in the treatment of hypertension, angina pectoris, cardiac arrhythmia, and most recently, cluster headaches. It is also an effective preventive medication for migraine...
) - Cardiac glycosides (i.e. digoxinDigoxinDigoxin INN , also known as digitalis, is a purified cardiac glycoside and extracted from the foxglove plant, Digitalis lanata. Its corresponding aglycone is digoxigenin, and its acetyl derivative is acetyldigoxin...
) - have limited use, apart from in the sedentary elderly patient
In addition to these agents, amiodarone has some AV node blocking effects (particularly when administered intravenously), and can be used in individuals when other agents are contraindicated or ineffective (particularly due to hypotension).
Diltiazem has been shown to be more effective than either digoxin or amiodarone.
Cardioversion
CardioversionCardioversion
Cardioversion is a medical procedure by which an abnormally fast heart rate or cardiac arrhythmia is converted to a normal rhythm, using electricity or drugs. Synchronized electrical cardioversion uses a therapeutic dose of electric current to the heart, at a specific moment in the cardiac cycle...
is a noninvasive conversion of an irregular heartbeat to a normal heartbeat using electrical or chemical means:
- Electrical cardioversion involves the restoration of normal heart rhythm through the application of a DC electrical shock.
- Chemical cardioversion is performed with drugs, such as amiodaroneAmiodaroneAmiodarone is an antiarrhythmic agent used for various types of tachyarrhythmias , both ventricular and supraventricular arrhythmias. Discovered in 1961, it was not approved for use in the United States until 1985...
, dronedaroneDronedaroneDronedarone is a drug by Sanofi-Aventis, mainly for the indication of cardiac arrhythmias. It was approved by the FDA on July 2, 2009. It is now available as 400 mg tablets in 20, 60 and 100 count packages...
, procainamideProcainamideProcainamide INN is a pharmaceutical antiarrhythmic agent used for the medical treatment of cardiac arrhythmias, classified by the Vaughan Williams classification system as class Ia.-History:...
, dofetilideDofetilideDofetilide is a class III antiarrhythmic agent.It is marketed under the trade name Tikosyn by Pfizer, and is available in the United States in capsules containing 125, 250, and 500 µg of dofetilide....
, ibutilideIbutilideIbutilide is a Class III antiarrhythmic agent that is indicated for acute cardioconversion of atrial fibrillation and atrial flutter of a recent onset to sinus rhythm. It exerts its antiarrhythmic effect by induction of slow inward sodium current, which prolongs action potential and refractory...
, propafenonePropafenonePropafenone is a class Ic anti-arrhythmic medication, which treats illnesses associated with rapid heart beats such as atrial and ventricular arrhythmias.-Mechanism of action:...
or flecainideFlecainideFlecainide acetate is a class Ic antiarrhythmic agent used to prevent and treat tachyarrhythmias . It is used to treat a variety of cardiac arrhythmias including paroxysmal atrial fibrillation , paroxysmal supraventricular tachycardia Flecainide acetate is a class Ic antiarrhythmic agent used to...
.
Vernakalant
Vernakalant
Vernakalant is an investigational drug under regulatory review for the acute conversion of atrial fibrillation...
has been found to safely and rapidly convert new onset atrial fibrillation.
Ablation
If rhythm control is desired and cannot be maintained by medication or cardioversion then catheter ablationAblation of atrial fibrillation
The ablation of atrial fibrillation is an invasive technique that is used in the treatment of Atrial fibrillation , one of the most common cardiac arrhythmias. Ablation is the removal or melting away of an unwanted structure or tissue...
may be attempted.
Thromboembolism
In atrial fibrillation, the lack of an organized atrial contraction can result in some stagnant blood in the left atrium (LA) or left atrial appendage (LAA). This lack of movement of blood can lead to thrombusThrombus
A thrombus , or blood clot, is the final product of the blood coagulation step in hemostasis. It is achieved via the aggregation of platelets that form a platelet plug, and the activation of the humoral coagulation system...
formation (blood clotting
Coagulation
Coagulation is a complex process by which blood forms clots. It is an important part of hemostasis, the cessation of blood loss from a damaged vessel, wherein a damaged blood vessel wall is covered by a platelet and fibrin-containing clot to stop bleeding and begin repair of the damaged vessel...
). If the clot becomes mobile and is carried away by the blood circulation, it is called an embolus
Embolus
An embolus is any detached, itinerant intravascular mass carried by circulation, which is capable of clogging arterial capillary beds at a site distant from its point of origin.By contrast there are non-traveling blockages that develop locally from vascular trauma or...
. An embolus proceeds through smaller and smaller arteries
Artery
Arteries are blood vessels that carry blood away from the heart. This blood is normally oxygenated, exceptions made for the pulmonary and umbilical arteries....
until it plugs one of them and prevents blood from flowing through the artery. This process results in end-organ damage due to loss of nutrients, oxygen, and removal of cellular waste products. Thrombus can form anywhere in the body, while emboli follow the blood circulation to specific points in the body. Emboli in the brain may results in a ischemic stroke or transient ischemic attack
Transient ischemic attack
A transient ischemic attack is a transient episode of neurologic dysfunction caused by ischemia – either focal brain, spinal cord or retinal – without acute infarction...
(TIA).
More than 90% of cases of thrombi associated with non-valvular atrial fibrillation evolve in the left atrial appendage. However, the LAA lies in close relation to the free wall of the left ventricle and thus the LAA's emptying and filling, which determines its degree of blood stagnation, may be helped by the motion of the wall of the left ventricle, if there is good ventricular function.
If the LA is enlarged, there is an increased risk of thrombi that originate in the LA. Moderate to severe, non-rheumatic
Rheumatic fever
Rheumatic fever is an inflammatory disease that occurs following a Streptococcus pyogenes infection, such as strep throat or scarlet fever. Believed to be caused by antibody cross-reactivity that can involve the heart, joints, skin, and brain, the illness typically develops two to three weeks after...
, mitral regurgitation
Mitral regurgitation
Mitral regurgitation , mitral insufficiency or mitral incompetence is a disorder of the heart in which the mitral valve does not close properly when the heart pumps out blood. It is the abnormal leaking of blood from the left ventricle, through the mitral valve, and into the left atrium, when...
(MR) reduces this risk of stroke. This risk reduction may be due to a beneficial stirring effect of the MR blood flow into the LA.
Mitral valve
Atrial fibrillation and a corresponding enlargement of the left atrium may cause an increase in the perimeter of the mitral valveMitral valve
The mitral valve is a dual-flap valve in the heart that lies between the left atrium and the left ventricle...
. The somewhat circular perimeter of the mitral valve is defined by the mitral annulus.
With a normal sinus rhythm, the mitral annulus undergoes dynamic changes during the cardiac cycle
Cardiac cycle
The cardiac cycle is a term referring to all or any of the events related to the flow or blood pressure that occurs from the beginning of one heartbeat to the beginning of the next. The frequency of the cardiac cycle is described by the heart rate. Each beat of the heart involves five major stages...
. For example, at the end of diastole
Diastole
Diastole is the period of time when the heart fills with blood after systole . Ventricular diastole is the period during which the ventricles are relaxing, while atrial diastole is the period during which the atria are relaxing...
the annular area is smaller than at the end of systole
Systole (medicine)
Systole is the contraction of the heart. Used alone, it usually means the contraction of the left ventricle.In all mammals, the heart has 4 chambers. The left and right ventricles pump together. The atria and ventricles pump in sequence...
. A possible reason for this dynamic size difference is that the coordinated contraction of the left atrium
Left atrium
The left atrium is one of the four chambers in the human heart. It receives oxygenated blood from the pulmonary veins, and pumps it into the left ventricle, via the mitral valve.-Foramen ovale:...
acts like a sphincter
Sphincter
A sphincter is an anatomical structure, or a circular muscle, that normally maintains constriction of a natural body passage or orifice and which relaxes as required by normal physiological functioning...
about the mitral annulus and reduces its size. This may be important for mitral valve competence so that it does not leak when the left ventricle pumps blood. However, when the left atrium fibrillates, this sphincter action is not possible and may contribute to, or result in, mitral regurgitation in some cases.
Epidemiology
Atrial fibrillation is the most common arrhythmia found in clinical practice. It also accounts for 1/3 of hospital admissions for cardiac rhythm disturbances, and the rate of admissions for AF has risen in recent years. Strokes from AF account for 6-24% of all ischemic strokes. Between 3-11% of those with AF have structurally normal hearts. Approximately 2.2 million individuals in the United States and 4.5 million in the European Union have AF.The incidence of atrial fibrillation increases with age. The prevalence in individuals over the age of 80 is about 8%. In developed countries, the number of patients with atrial fibrillation is likely to increase during the next 50 years, owing to the growing proportion of elderly individuals.
History
Because the diagnosis of atrial fibrillation requires measurement of the electrical activity of the heart, atrial fibrillation was not truly described until 1874, when Edmé Félix Alfred Vulpian observed the irregular atrial electrical behavior that he termed "fremissement fibrillaire" in dog hearts. In the mid-eighteenth century, Jean-Baptiste de SénacJean-Baptiste de Sénac
Jean-Baptiste de Sénac was a French physician who was born in the town of Lombez. Details of his early life are sketchy, however it is generally thought that he studied medicine at the University of Leyden, and later in London, where one of his instructors was John Freind...
made note of dilated, irritated atria in people with mitral stenosis
Mitral stenosis
Mitral stenosis is a valvular heart disease characterized by the narrowing of the orifice of the mitral valve of the heart.-Signs and symptoms:Symptoms of mitral stenosis include:...
. The irregular pulse associated with AF was first recorded in 1876 by Carl Wilhelm Hermann Nothnagel
Carl Nothnagel
Carl Wilhelm Hermann Nothnagel was a German internist born in Alt-Lietzegöricke , nearby Bärwalde in der Neumark , Neumark, Brandenburg....
and termed "delirium cordis", stating that "[I]n this form of arrhythmia the heartbeats follow each other in complete irregularity. At the same time, the height and tension of the individual pulse waves are continuously changing". Correlation of delirium cordis with the loss of atrial contraction as reflected in the loss of a waves in the jugular venous pulse
Jugular venous pressure
The jugular venous pressure is the indirectly observed pressure over the venous system...
was made by Sir James MacKenzie in 1904. Willem Einthoven
Willem Einthoven
Willem Einthoven was a Dutch doctor and physiologist. He invented the first practical electrocardiogram in 1903 and received the Nobel Prize in Medicine in 1924 for it....
published the first ECG showing AF in 1906. The connection between the anatomic and electrical manifestations of AF and the irregular pulse of delirium cordis was made in 1909 by Carl Julius Rothberger, Heinrich Winterberg, and Sir Thomas Lewis.
External links
- American Heart Association page on atrial fibrillation