Tachycardia
Encyclopedia
Tachycardia comes from the Greek words tachys (rapid or accelerated) and kardia (of the heart). Tachycardia typically refers to a heart rate
that exceeds the normal range for a resting heart rate (heart rate in an inactive or sleeping individual). It can be dangerous depending on the speed and type of rhythm.
When the heart beats excessively rapidly, the heart pumps less efficiently and provides less blood flow to the rest of the body, including the heart itself. The increased heart rate also leads to increased work and oxygen demand by the heart, which can lead to rate related ischemia
.
An electrocardiogram
(ECG) is used to classify the type of tachycardia. They may be classified into narrow and wide complex based on the QRS complex
. Presented in the order of most to least common they are:
Narrow complex
Wide complex
Tachycardias may be classified as either narrow complex tachycardias (supraventricular tachycardias) or wide complex tachycardias. Narrow and widerefer to the width of the QRS complex
on the ECG. Narrow complex tachycardias tend to originate in the atria, while wide complex tachycardias tend to originate in the ventricles. Tachycardias can be further classified as either regular or irregular.
. If blood pressure decreases, the heart beats faster in an attempt to raise it. This is called reflex
tachycardia. This can happen in response to a decrease in blood volume (through dehydration
or bleeding
), or an unexpected change in blood flow
. The most common cause of the latter is orthostatic hypotension
(also called postural hypotension). Fever
, hyperventilation
and severe infections can also cause tachycardia, primarily due to increase in metabolic demands.
An increase in sympathetic nervous system
stimulation causes the heart rate to increase, both by the direct action of sympathetic nerve fibers on the heart and by causing the endocrine system to release hormone
s such as epinephrine (adrenaline)
, which have a similar effect. Increased sympathetic stimulation is usually due to physical or psychological stress. This is the basis for the so-called "Fight or Flight"
response, but such stimulation can also be induced by stimulant
s such as ephedrine
, amphetamines or cocaine
. Certain endocrine disorders such as pheochromocytoma
can also cause epinephrine release and can result in tachycardia independent nervous system stimulation. Hyperthyroidism
can also cause tachycardia.
. Ventricular tachycardia is a common, and often lethal, complication of a myocardial infarction
(heart attack).
Exercise-induced ventricular tachycardia is a phenomenon related to sudden death
s, especially in patients with severe heart disease (ischemia
, acquired valvular heart
and congenital heart disease) accompanied with left ventricular
dysfunction
.
Both of these rhythms normally last for only a few second
s to minute
s (paroxysmal tachycardia
), but if VT persists it is extremely dangerous, often leading to ventricular fibrillation
.
is one of the most common cardiac arrhythmias. It is generally an irregular, narrow complex rhythm. However, it may show wide QRS complexes on the ECG if a bundle branch block
is present. At high rates, the QRS complex may also become wide due to the Ashman phenomenon
. It may be difficult to determine the rhythm's regularity when the rate exceeds 150 beats per minute. Depending on the patient's health and other variables such as medications taken for rate control, atrial fibrillation may cause heart rates that span from 50 to 250 beats per minute (or even higher if an accessory pathway
is present). However, new onset atrial fibrillation tends to present with rates between 100 and 150 beats per minute. This also induces massive Diarrhea
.
(AVNRT) is the most common reentrant tachycardia. It is a regular narrow complex tachycardia
that usually responds well to the Valsalva maneuver
or the drug adenosine. However, unstable patients sometimes require synchronized cardioversion
. Definitive care may include catheter ablation
.
for its maintenance. AVRT may involve orthodromic conduction (where the impulse travels down the AV node to the ventricles and back up to the atria through the accessory pathway) or antidromic conduction (which the impulse travels down the accessory pathway and back up to the atria through the AV node). Orthodromic conduction usually results in a narrow complex tachycardia, and antidromic conduction usually results in a wide complex tachycardia that often mimics ventricular tachycardia
. Most antiarrhythmics are contraindicated in the emergency treatment of AVRT, because they may paradoxically increase conduction across the accessory pathway.
is about to occur.
is recommended.
Heart rate
Heart rate is the number of heartbeats per unit of time, typically expressed as beats per minute . Heart rate can vary as the body's need to absorb oxygen and excrete carbon dioxide changes, such as during exercise or sleep....
that exceeds the normal range for a resting heart rate (heart rate in an inactive or sleeping individual). It can be dangerous depending on the speed and type of rhythm.
Definition
The upper threshold of a normal human heart rate is based upon age. Tachycardia for different age groups is as listed below:- 1–2 days: >159 beats per minute (bpm)
- 3–6 days: >166 bpm
- 1–3 weeks: >182 bpm
- 1–2 months: >179 bpm
- 3–5 months: >186 bpm
- 6–11 months: >169 bpm
- 1–2 years: >151 bpm
- 3–4 years: >137 bpm
- 5–7 years: >133 bpm
- 8–11 years: >130 bpm
- 12–15 years: >119 bpm
- >15 years – adult: >100 bpm
When the heart beats excessively rapidly, the heart pumps less efficiently and provides less blood flow to the rest of the body, including the heart itself. The increased heart rate also leads to increased work and oxygen demand by the heart, which can lead to rate related ischemia
Ischemia
In medicine, ischemia is a restriction in blood supply, generally due to factors in the blood vessels, with resultant damage or dysfunction of tissue. It may also be spelled ischaemia or ischæmia...
.
Differential diagnosis
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) is used to classify the type of tachycardia. They may be classified into narrow and wide complex based on the 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...
. Presented in the order of most to least common they are:
Narrow complex
- Sinus tachycardiaSinus tachycardiaSinus tachycardia is a heart rhythm with elevated rate of impulses originating from the sinoatrial node, defined as a rate greater than 100 beats/min in an average adult. The normal heart rate in the average adult ranges from 60–100 beats/min...
, which originates from the sino-atrial (SA) node, near the base of the superior vena cavaSuperior vena cavaThe superior vena cava is truly superior, a large diameter, yet short, vein that carries deoxygenated blood from the upper half of the body to the heart's right atrium...
. - Atrial fibrillationAtrial fibrillationAtrial fibrillation is the most common cardiac arrhythmia . It is a common cause of irregular heart beat, identified clinically by taking a pulse. Chaotic electrical activity in the two upper chambers of the heart result in the muscle fibrillating , instead of achieving coordinated contraction...
- Atrial flutterAtrial flutterAtrial 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...
- AV nodal reentrant tachycardiaAV nodal reentrant tachycardiaAV nodal reentrant tachycardia , or atrioventricular nodal reentrant tachycardia, is a type of tachycardia of the heart. It is a type of supraventricular tachycardia , meaning that it originates from a location within the heart above the bundle of His. AV nodal reentrant tachycardia is the most...
- Accessory pathway mediated tachycardiaWolff-Parkinson-White syndromeWolff–Parkinson–White syndrome is a disorder of the heart in which the ventricles of the heart contract prematurely due to an accessory pathway known as the bundle of Kent. This accessory pathway is an abnormal electrical communication from the atria to the ventricles...
- Atrial tachycardiaAtrial tachycardiaAtrial tachycardia is a type of atrial arrhythmia in which the heart's electrical impulse comes from an ectopic atrial pacemaker rather than from the SA node. Atrial tachycardias are characterized by very regular rates ranging from 140–220 bpm....
- Multifocal atrial tachycardiaMultifocal atrial tachycardiaMultifocal atrial tachycardia is a cardiac arrhythmia, specifically a type of supraventricular tachycardia."Multifocal atrial rhythm" is the condition in the absence of tachycardia.-Causes and epidemiology:It is more common in the elderly....
- Junctional tachycardiaJunctional tachycardiaJunctional tachycardia is a form of supraventricular tachycardia characterized by involvement of the AV node. It can be contrasted to atrial tachycardia. It is a tachycardia associated with the generation of impulses in a locus in the region of the atrioventricular node.It can be associated with...
Wide complex
- Ventricular tachycardiaVentricular tachycardiaVentricular tachycardia is a tachycardia, or fast heart rhythm, that originates in one of the ventricles of the heart...
, any tachycardia which originates in the ventriclesVentricle (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...
.
Tachycardias may be classified as either narrow complex tachycardias (supraventricular tachycardias) or wide complex tachycardias. Narrow and widerefer to the width of the 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...
on the ECG. Narrow complex tachycardias tend to originate in the atria, while wide complex tachycardias tend to originate in the ventricles. Tachycardias can be further classified as either regular or irregular.
Sinus
The body has several feedback mechanisms to maintain adequate blood flow and blood pressureBlood pressure
Blood pressure is the pressure exerted by circulating blood upon the walls of blood vessels, and is one of the principal vital signs. When used without further specification, "blood pressure" usually refers to the arterial pressure of the systemic circulation. During each heartbeat, BP varies...
. If blood pressure decreases, the heart beats faster in an attempt to raise it. This is called reflex
Reflex
A reflex action, also known as a reflex, is an involuntary and nearly instantaneous movement in response to a stimulus. A true reflex is a behavior which is mediated via the reflex arc; this does not apply to casual uses of the term 'reflex'.-See also:...
tachycardia. This can happen in response to a decrease in blood volume (through 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...
or bleeding
Bleeding
Bleeding, technically known as hemorrhaging or haemorrhaging is the loss of blood or blood escape from the circulatory system...
), or an unexpected change in blood flow
Blood flow
Blood flow is the continuous running of blood in the cardiovascular system.The human body is made up of several processes all carrying out various functions. We have the gastrointestinal system which aids the digestion and the absorption of food...
. The most common cause of the latter is orthostatic hypotension
Orthostatic hypotension
Orthostatic hypotension, also known as postural hypotension, orthostasis, and colloquially as head rush or dizzy spell, is a form of hypotension in which a person's blood pressure suddenly falls when the person stands up or stretches. The decrease is typically greater than 20/10 mm Hg, and may be...
(also called postural hypotension). Fever
Fever
Fever is a common medical sign characterized by an elevation of temperature above the normal range of due to an increase in the body temperature regulatory set-point. This increase in set-point triggers increased muscle tone and shivering.As a person's temperature increases, there is, in...
, hyperventilation
Hyperventilation
Hyperventilation or overbreathing is the state of breathing faster or deeper than normal, causing excessive expulsion of circulating carbon dioxide. It can result from a psychological state such as a panic attack, from a physiological condition such as metabolic acidosis, can be brought about by...
and severe infections can also cause tachycardia, primarily due to increase in metabolic demands.
An increase in sympathetic nervous system
Sympathetic nervous system
The sympathetic nervous system is one of the three parts of the autonomic nervous system, along with the enteric and parasympathetic systems. Its general action is to mobilize the body's nervous system fight-or-flight response...
stimulation causes the heart rate to increase, both by the direct action of sympathetic nerve fibers on the heart and by causing the endocrine system to release hormone
Hormone
A hormone is a chemical released by a cell or a gland in one part of the body that sends out messages that affect cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. In essence, it is a chemical messenger that transports a signal from one...
s such as epinephrine (adrenaline)
Epinephrine
Epinephrine is a hormone and a neurotransmitter. It increases heart rate, constricts blood vessels, dilates air passages and participates in the fight-or-flight response of the sympathetic nervous system. In chemical terms, adrenaline is one of a group of monoamines called the catecholamines...
, which have a similar effect. Increased sympathetic stimulation is usually due to physical or psychological stress. This is the basis for the so-called "Fight or Flight"
Fight-or-flight response
The fight-or-flight response was first described by Walter Bradford Cannon....
response, but such stimulation can also be induced by stimulant
Stimulant
Stimulants are psychoactive drugs which induce temporary improvements in either mental or physical function or both. Examples of these kinds of effects may include enhanced alertness, wakefulness, and locomotion, among others...
s such as ephedrine
Ephedrine
Ephedrine is a sympathomimetic amine commonly used as a stimulant, appetite suppressant, concentration aid, decongestant, and to treat hypotension associated with anaesthesia....
, amphetamines or cocaine
Cocaine
Cocaine is a crystalline tropane alkaloid that is obtained from the leaves of the coca plant. The name comes from "coca" in addition to the alkaloid suffix -ine, forming cocaine. It is a stimulant of the central nervous system, an appetite suppressant, and a topical anesthetic...
. Certain endocrine disorders such as pheochromocytoma
Pheochromocytoma
A pheochromocytoma or phaeochromocytoma is a neuroendocrine tumor of the medulla of the adrenal glands , or extra-adrenal chromaffin tissue that failed to involute after birth and secretes excessive amounts of catecholamines, usually noradrenaline , and adrenaline to a lesser extent...
can also cause epinephrine release and can result in tachycardia independent nervous system stimulation. 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...
can also cause tachycardia.
Ventricular
Ventricular tachycardia (VT or V-tach) is a potentially life-threatening cardiac arrhythmia that originates in the ventricles. It is usually a regular, wide complex tachycardia with a rate between 120 and 250 beats per minute. Ventricular tachycardia has the potential of degrading to the more serious ventricular fibrillationVentricular fibrillation
Ventricular fibrillation is a condition in which there is uncoordinated contraction of the cardiac muscle of the ventricles in the heart, making them quiver rather than contract properly. Ventricular fibrillation is a medical emergency and most commonly identified arrythmia in cardiac arrest...
. Ventricular tachycardia is a common, and often lethal, complication of a myocardial infarction
Myocardial infarction
Myocardial infarction or acute myocardial infarction , commonly known as a heart attack, results from the interruption of blood supply to a part of the heart, causing heart cells to die...
(heart attack).
Exercise-induced ventricular tachycardia is a phenomenon related to sudden death
Cardiac arrest
Cardiac arrest, is the cessation of normal circulation of the blood due to failure of the heart to contract effectively...
s, especially in patients with severe heart disease (ischemia
Ischemia
In medicine, ischemia is a restriction in blood supply, generally due to factors in the blood vessels, with resultant damage or dysfunction of tissue. It may also be spelled ischaemia or ischæmia...
, acquired valvular heart
Valvular 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...
and congenital heart disease) accompanied with left ventricular
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...
dysfunction
Dysfunction
Dysfunction can refer to:* Abnormality * Dysfunctional family* Sexual dysfunction* Dysfunction , an album by the rock band Staind...
.
Both of these rhythms normally last for only a few second
Second
The second is a unit of measurement of time, and is the International System of Units base unit of time. It may be measured using a clock....
s to minute
Minute
A minute is a unit of measurement of time or of angle. The minute is a unit of time equal to 1/60th of an hour or 60 seconds. In the UTC time scale, a minute on rare occasions has 59 or 61 seconds; see leap second. The minute is not an SI unit; however, it is accepted for use with SI units...
s (paroxysmal tachycardia
Paroxysmal tachycardia
Paroxysmal tachycardia is a form of tachycardia which begins and ends in an acute manner.It is also known as "Bouveret-Hoffmann syndrome".-Classification:It can be divided by the origin:* supraventricular tachycardia...
), but if VT persists it is extremely dangerous, often leading to ventricular fibrillation
Ventricular fibrillation
Ventricular fibrillation is a condition in which there is uncoordinated contraction of the cardiac muscle of the ventricles in the heart, making them quiver rather than contract properly. Ventricular fibrillation is a medical emergency and most commonly identified arrythmia in cardiac arrest...
.
Supraventricular
This is a type tachycardia that originates from above the ventricles, such as the atria. It is sometimes known as paroxysmal atrial tachycardia (PAT). Several types of supraventricular tachycardia are known to exist.Atrial fibrillation
Atrial fibrillationAtrial fibrillation
Atrial fibrillation is the most common cardiac arrhythmia . It is a common cause of irregular heart beat, identified clinically by taking a pulse. Chaotic electrical activity in the two upper chambers of the heart result in the muscle fibrillating , instead of achieving coordinated contraction...
is one of the most common cardiac arrhythmias. It is generally an irregular, narrow complex rhythm. However, it may show wide QRS complexes on the ECG if a bundle branch block
Bundle branch block
A bundle branch block refers to a defect of the heart's electrical conduction system.-Anatomy and physiology:The heart's electrical activity begins in the sinoatrial node , which is situated on the upper right atrium. The impulse travels next through the left and right atria and summates at the...
is present. At high rates, the QRS complex may also become wide due to the Ashman phenomenon
Ashman phenomenon
First described by Gouaux and Ashman in 1947, Ashman phenomenon, also known as Ashman beats, describes a particular type of wide complex tachycardia that is often seen in atrial fibrillation...
. It may be difficult to determine the rhythm's regularity when the rate exceeds 150 beats per minute. Depending on the patient's health and other variables such as medications taken for rate control, atrial fibrillation may cause heart rates that span from 50 to 250 beats per minute (or even higher if an accessory pathway
Wolff-Parkinson-White syndrome
Wolff–Parkinson–White syndrome is a disorder of the heart in which the ventricles of the heart contract prematurely due to an accessory pathway known as the bundle of Kent. This accessory pathway is an abnormal electrical communication from the atria to the ventricles...
is present). However, new onset atrial fibrillation tends to present with rates between 100 and 150 beats per minute. This also induces massive 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...
.
AV nodal reentrant tachycardia
AV nodal reentrant tachycardiaAV nodal reentrant tachycardia
AV nodal reentrant tachycardia , or atrioventricular nodal reentrant tachycardia, is a type of tachycardia of the heart. It is a type of supraventricular tachycardia , meaning that it originates from a location within the heart above the bundle of His. AV nodal reentrant tachycardia is the most...
(AVNRT) is the most common reentrant tachycardia. It is a regular narrow complex tachycardia
Supraventricular tachycardia
Supraventricular tachycardia is a general term that refers to any rapid heart rhythm originating above the ventricular tissue. Supraventricular tachycardias can be contrasted to the potentially more dangerous ventricular tachycardias - rapid rhythms that originate within the ventricular...
that usually responds well to the Valsalva maneuver
Valsalva maneuver
The Valsalva maneuver or Valsalva manoeuvre is performed by moderately forceful attempted exhalation against a closed airway, usually done by closing one's mouth and pinching one's nose shut...
or the drug adenosine. However, unstable patients sometimes require synchronized 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...
. Definitive care may include catheter ablation
Catheter ablation
Catheter ablation is an invasive procedure used to remove a faulty electrical pathway from the hearts of those who are prone to developing cardiac arrhythmias such as atrial fibrillation, atrial flutter, supraventricular tachycardias and Wolff-Parkinson-White syndrome.It involves advancing several...
.
AV reentrant tachycardia
AV reentrant tachycardia (AVRT) requires an accessory pathwayWolff-Parkinson-White syndrome
Wolff–Parkinson–White syndrome is a disorder of the heart in which the ventricles of the heart contract prematurely due to an accessory pathway known as the bundle of Kent. This accessory pathway is an abnormal electrical communication from the atria to the ventricles...
for its maintenance. AVRT may involve orthodromic conduction (where the impulse travels down the AV node to the ventricles and back up to the atria through the accessory pathway) or antidromic conduction (which the impulse travels down the accessory pathway and back up to the atria through the AV node). Orthodromic conduction usually results in a narrow complex tachycardia, and antidromic conduction usually results in a wide complex tachycardia that often mimics ventricular tachycardia
Ventricular tachycardia
Ventricular tachycardia is a tachycardia, or fast heart rhythm, that originates in one of the ventricles of the heart...
. Most antiarrhythmics are contraindicated in the emergency treatment of AVRT, because they may paradoxically increase conduction across the accessory pathway.
Junctional tachycardia
Junctional tachycardia is an automatic tachycardia originating in the AV junction. It tends to be a regular, narrow complex tachycardia and may be a sign of digitalis toxicity.Management
The management of tachycardia depends on its type (wide complex versus narrow complex), whether or not the person is stable or unstable, and if the instability is due to the tachycardia. Unstable means that either important organ functions are affected or cardiac arrestCardiac arrest
Cardiac arrest, is the cessation of normal circulation of the blood due to failure of the heart to contract effectively...
is about to occur.
Stable
In those who are stable treatment is determined by the exact ECG findings: wide versus narrow complex, regular versus irregular heart rate, and whether the QRS is monomorphic or polymorphic.Unstable
In those who are unstable with a narrow complex tachycardia, intravenous adenosine may be attempted. In all others immediate 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 recommended.
External links
- Dysautonomia Youth Network of America, Inc.
- Postural Orthostatic Tachycardia Syndrome - overview from Dysautonomia Information Network
- Heart Arrhythmias Respond to Ablation UCLA Healthcare
- Heart Rate Calculator Heart Rate Calculator for Diagnosis of Tachycardia
- Drugs most commonly reported to the FDA with the adverse event Tachycardia in AERS