Aortic valve stenosis
Encyclopedia
Aortic valve stenosis is a disease of the heart valves
in which the opening of the aortic valve
is narrowed. The aortic valve is the valve between the left ventricle
of the heart and the aorta
, which is the largest artery in the body and carries the entire output of blood.
The aortic valve
normally consists of three leaflets (trileaflets). When the left ventricle
(LV) contracts, it forces blood through the valve to the aorta
and then to the rest of the body. When the LV expands again, the aortic valve prevents the blood from returning to the ventricle. When the opening of the aortic valve becomes narrowed or constricted (stenotic
), the blood can't be pumped adequately and the pressure in the left ventricle increases. Initially, the LV compensates by thickening its walls (myocardial hypertrophy) in order to maintain adequate pumping pressure. The type of hypertrophy most commonly seen in AS is concentric hypertrophy, in which the walls of the LV are (approximately) equally thickened. In the later stages, the left ventricle dilates, the wall thins, and the systolic function deteriorates.
(30-40% of cases) and acute rheumatic fever (less than 10% of cases).
Normal valves have three leafs (tricuspid), but some valves have two leafs (bicuspid). Typically, aortic stenosis due to calcification of a bicuspid valve appears earlier, in the 40s and 50s, whereas that due to calcification of a normal valve appears later, in the 70s and 80s. Hypertension
, diabetes mellitus
, hyperlipoproteinemia and uremia
may speed up the process.
(CHF) carries a grave prognosis in patients with AS. Patients with CHF that is attributed to AS have a 2 year mortality rate of 50%, if the aortic valve is not replaced.
CHF in the setting of AS is due to a combination of systolic dysfunction (a decrease in the ejection fraction
) and diastolic dysfunction
(elevated filling pressure of the LV).
(fainting spells) from aortic valve stenosis is usually exertional. In the setting of heart failure it increases the risk of death. In patients with syncope, the 3 year mortality rate is 50%, if the aortic valve is not replaced.
It is unclear why aortic stenosis causes syncope. One popular theory is that severe AS produces a nearly fixed cardiac output
. When the patient exercises, their peripheral vascular resistance will decrease as the blood vessels of the skeletal muscles dilate to allow the muscles to receive more blood to allow them to do more work. This decrease in peripheral vascular resistance is normally compensated for by an increase in the cardiac output. Since patients with severe AS cannot increase their cardiac output, the blood pressure falls and the patient will syncopize due to decreased blood perfusion to the brain
.
A second theory as to why syncope may occur in AS is that during exercise, the high pressures generated in the hypertrophied LV cause a vasodepressor response, which causes a secondary peripheral vasodilation
that, in turn, causes decreased blood flow to the brain
. Indeed, in aortic stenosis, because of the fixed obstruction to bloodflow out from the heart, it may be impossible for the heart to increase its output to offset peripheral vasodilation.
A third mechanism may sometimes be operative. Due to the hypertrophy of the left ventricle
in aortic stenosis, including the consequent inability of the coronary arteries to adequately supply blood to the myocardium (see "Angina" below), arrhythmias may develop. These can lead to syncope
.
Finally, in calcific aortic stenosis at least, the calcification in and around the aortic valve can progress and extend to involve the electrical conduction system of the heart
. If that occurs, the result may be heart block
- a potentially lethal condition of which syncope may be a symptom.
Angina in the setting of AS is secondary to the left ventricular hypertrophy
(LVH) that is caused by the constant production of increased pressure required to overcome the pressure gradient caused by the AS. While the myocardium (i.e., heart muscle) of the LV gets thicker, the arteries that supply the muscle do not get significantly longer or bigger, so the muscle may become ischemic (i.e., does not receive an adequate blood supply). The ischemia
may first be evident during exercise, when the heart muscle requires increased blood supply to compensate for the increased workload. The individual may complain of exertional angina. At this stage, a stress test
with imaging may be suggestive of ischemia.
Eventually, however, the muscle will require more blood supply at rest than can be supplied by the coronary artery branches. At this point there may be signs of ventricular strain pattern (ST segment depression and T wave inversion) on the EKG, suggesting subendocardial ischemia. The subendocardium is the region that becomes ischemic because it is the most distant from the epicardial coronary arteries.
, aortic stenosis is associated with angiodysplasia
of the colon
. Recent research has shown that the stenosis causes a form of von Willebrand disease
by breaking down its associated coagulation
factor (factor VIII
-associated antigen, also called von Willebrand factor
), due to increased turbulence around the stenosed valve.
and can sometimes be detected during routine examination of the heart and circulatory system. Good evidence exists to demonstrate that certain characteristics of the peripheral pulse can rule in the diagnosis. In particular, there may be a slow and/or sustained upstroke of the arterial pulse, and the pulse may be of low volume. This is sometimes referred to as pulsus parvus et tardus. There may also be a noticeable delay between the first heart sound
(on auscultation
) and the corresponding pulse in the carotid artery (so-called 'apical-carotid delay'). In similar manner, there may be a delay between the appearance of each pulse in the brachial artery (in the arm) and the radial artery (in the wrist).
The first heart sound may be followed by a sharp ejection sound ("ejection click") best heard at the lower left sternal border and the apex, and, thus, appear to be "split". The ejection sound, caused by the impact of left ventricular outflow against the partially fused aortic valve leaflets, is more commonly associated with a mobile bicuspid aortic valve
than an immobile calcified aortic valve. The intensity of this sound does not vary with respiration, which helps distinguish it from the ejection click produced by a stenotic pulmonary valve, which will diminish slightly in intensity during inspiration.
An easily heard systolic
, crescendo-decrescendo (i.e., 'ejection') murmur
is heard loudest at the upper right sternal border, at the 2nd right intercostal space, and radiates to the carotid arteries
bilaterally. The murmur increases with squatting, decreases with standing and isometric muscular contraction, which helps distinguish it from hypertrophic obstructive cardiomyopathy (HOCM). The murmur is louder during expiration, but is also easily heard during inspiration. The more severe the degree of the stenosis, the later the peak occurs in the crescendo-decrescendo of the murmur.
The second heart sound (A2) tends to become decreased and softer as the aortic stenosis becomes more severe. This is a result of the increasing calcification of the valve preventing it from "snapping" shut and producing a sharp, loud sound. Due to increases in left ventricular pressure from the stenotic aortic valve, over time the ventricle may hypertrophy, resulting in a diastolic dysfunction. As a result, one may hear a fourth heart sound
due to the stiff ventricle. With continued increases in ventricular pressure, dilatation of the ventricle will occur, and a third heart sound may be manifest.
Finally, aortic stenosis often co-exists with some degree of aortic insufficiency
(aortic regurgitation). Hence, the physical exam in aortic stenosis may also reveal signs of the latter, for example an early diastolic decrescendo murmur. Indeed, when both valve abnormalities are present, the expected findings of either may be modified or may not even be present. Rather, new signs that reflect the presence of simultaneous aortic stenosis and insufficiency, e.g., pulsus bisferiens
, emerge.
According to a meta analysis, the most useful findings for ruling in aortic stenosis in the clinical setting were slow rate of rise of the carotid pulse(positive likelihood ratio
ranged 2.8–130 across studies), mid to late peak intensity of the murmur(positive likelihood ratio, 8.0–101), and decreased intensity of the second heart sound (positive likelihood ratio, 3.1–50).
Other peripheral signs include:
(LVH) are common in aortic stenosis and arise as a result of the stenosis having placed a chronically high pressure load on the left ventricle
(with LVH being the expected response to chronic pressure loads on the left ventricle no matter what the cause).
As noted above, the calcification process that occurs in aortic stenosis can progress to extend beyond the aortic valve and into the electrical conduction system of the heart
. Evidence of this phenomenon may include heart block
that is apparent on the ECG but otherwise undetectable.
Echocardiogram (heart ultrasound) is the best non-invasive test to evaluate the aortic valve anatomy and function.
The aortic valve area can be calculated
non-invasively using echocardiographic flow velocities. Using the velocity of the blood through the valve, the pressure gradient across can be calculated by the modified Bernoulli's equation:
, heart failure or co-existent aortic regurgitation.
Echocardiogram may also show left ventricular hyperthrophy, thickened and immobile aortic valve and dilated aortic root. However, it may appear deceptively normal in acute cases.
can also assist in the diagnosis, showing calcific aortic valve, and, in longstanding disease, enlarged left ventricle and atrium.
. To lessen the chance of developing that serious complication, people with AS are usually advised to take antibiotic prophylaxis around the time of certain dental/medical/surgical procedures. Such procedures may include dental extraction, deep scaling of the teeth, gum surgery, dental implants, treatment of esophageal varices
, dilation of esophageal stricture
s, gastrointestinal surgery where the intestinal mucosa will be disrupted, prostate
surgery, urethral stricture
dilation, and cystoscopy
. Note that routine upper and lower GI endoscopy
(i.e., gastroscopy and colonoscopy
), with or without biopsy
, are not usually considered indications for antibiotic prophylaxis.
Notwithstanding the foregoing, the American Heart Association has recently changed its recommendations regarding antibiotic prophylaxis for endocarditis. Specifically, as of 2007, it is recommended that such prophylaxis be limited only to 1. those with prosthetic heart valves, 2. those with previous episode(s) of endocarditis, and 3. those with certain types of congenital heart disease.[Dead Link]
Since the stenosed aortic valve may limit the heart's output, people with aortic stenosis are at risk of syncope
and dangerously low blood pressure should they use any of a number of medications for cardiovascular diseases that often co-exist with aortic stenosis. Examples include nitroglycerin, nitrates, ACE inhibitor
s, terazosin
(Hytrin), and hydralazine
. Note that all of these substances lead to peripheral vasodilation
. Under normal circumstances, in the absence of aortic stenosis, the heart is able to increase its output and thereby offset the effect of the dilated blood vessels. In some cases of aortic stenosis, however, due to the obstruction of blood flow out of the heart caused by the stenosed aortic valve, cardiac output
cannot be increased. Low blood pressure or syncope
may ensue.
Then, and only then, in neonates, will the following advice be appropriate.
1.Stabilize with prostaglandin E1(PGE) infusion to maintain cardiac output through PDA.
2. Inotropic support as needed.
There is no medical treatment for aortic stenosis. Symptoms need assessment for surgery, severe symptoms may need urgent surgery. Meanwhile, dysrythmias or hypercholesterolaemia may need medical treatment.
. In severe cases, echocardiography is performed every 3–6 months. In both moderate and mild cases, the patient should immediately make a revisit or be admitted for inpatient care if any new related symptoms appear.
(AVR). AVR has been the standard of care for aortic stenosis for several decades.
(AAC), or Aortic Valve Bypass (AVB), has been shown to be an effective treatment for aortic stenosis. There is long-term stability of the left ventricular hemodynamics
after AVB, with no further biologic progression of native aortic valve stenosis. Once the pressure gradient across the native valve is substantially reduced, the narrowing and calcification of the native valve halts.
implantation of an aortic valve prosthesis
in high-risk patients with aortic stenosis results in marked hemodynamic and clinical improvement when successfully completed. Medium- and long-term results are unknown. When selecting the optimal therapy for individual patients, the percutaneous approach must be carefully weighed against the excellent results achieved with conventional surgery.
Since calcific aortic stenosis shares many pathological features and risk factors with atherosclerosis
, and since atherosclerosis may be prevented and/or reversed by cholesterol lowering, there has been interest in attempting to modify the course of calcific aortic stenosis by cholesterol lowering with statin
drugs. Although a number of small, observational studies demonstrated an association between lowered cholesterol and decreased progression, and even regression, of calcific aortic stenosis, a recent, large randomized clinical trial, published in 2005, failed to find any predictable effect of cholesterol lowering on calcific aortic stenosis. A 2007 study did demonstrate a slowing of aortic stenosis with the statin rosuvastatin
. However, what is likely to be considered the definitive trial, published in the New England Journal of Medicine in 2008, failed to find any beneficial effect of intensive cholesterol lowering on the course of aortic stenosis.
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...
in which the opening of the aortic valve
Aortic valve
The aortic valve is one of the valves of the heart. It is normally tricuspid , although in 1% of the population it is found to be congenitally bicuspid . It lies between the left ventricle and the aorta....
is narrowed. The aortic valve is the valve between the left ventricle
Left ventricle
The left ventricle is one of four chambers in the human heart. It receives oxygenated blood from the left atrium via the mitral valve, and pumps it into the aorta via the aortic valve.-Shape:...
of the heart and the aorta
Aorta
The aorta is the largest artery in the body, originating from the left ventricle of the heart and extending down to the abdomen, where it branches off into two smaller arteries...
, which is the largest artery in the body and carries the entire output of blood.
Pathophysiology
Aortic valve
The aortic valve is one of the valves of the heart. It is normally tricuspid , although in 1% of the population it is found to be congenitally bicuspid . It lies between the left ventricle and the aorta....
normally consists of three leaflets (trileaflets). When the left ventricle
Left ventricle
The left ventricle is one of four chambers in the human heart. It receives oxygenated blood from the left atrium via the mitral valve, and pumps it into the aorta via the aortic valve.-Shape:...
(LV) contracts, it forces blood through the valve to the aorta
Aorta
The aorta is the largest artery in the body, originating from the left ventricle of the heart and extending down to the abdomen, where it branches off into two smaller arteries...
and then to the rest of the body. When the LV expands again, the aortic valve prevents the blood from returning to the ventricle. When the opening of the aortic valve becomes narrowed or constricted (stenotic
Stenosis
A stenosis is an abnormal narrowing in a blood vessel or other tubular organ or structure.It is also sometimes called a stricture ....
), the blood can't be pumped adequately and the pressure in the left ventricle increases. Initially, the LV compensates by thickening its walls (myocardial hypertrophy) in order to maintain adequate pumping pressure. The type of hypertrophy most commonly seen in AS is concentric hypertrophy, in which the walls of the LV are (approximately) equally thickened. In the later stages, the left ventricle dilates, the wall thins, and the systolic function deteriorates.
Etiology
Aortic stenosis is most commonly caused by age-related progressive calcification of the normal tricuspid aortic valve (>50% of cases). Other causes include calcification of a congenital bicuspid aortic valveBicuspid aortic valve
A bicuspid aortic valve is most commonly a congenital condition of the aortic valve where two of the aortic valvular leaflets fuse during development resulting in a valve that is bicuspid instead of the normal tricuspid configuration. Normally the only cardiac valve that is bicuspid is the mitral...
(30-40% of cases) and acute rheumatic fever (less than 10% of cases).
Normal valves have three leafs (tricuspid), but some valves have two leafs (bicuspid). Typically, aortic stenosis due to calcification of a bicuspid valve appears earlier, in the 40s and 50s, whereas that due to calcification of a normal valve appears later, in the 70s and 80s. 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...
, diabetes mellitus
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...
, hyperlipoproteinemia and uremia
Uremia
Uremia or uraemia is a term used to loosely describe the illness accompanying kidney failure , in particular the nitrogenous waste products associated with the failure of this organ....
may speed up the process.
Prevalence
Approximately 2% of people over the age of 65, 3% of people over age 75, and 4% percent of people over age 85 have aortic valve stenosis. The prevalence is increasing with the aging population in North America and Europe.Symptoms of aortic stenosis
Symptoms related to aortic stenosis depend on the degree of valve stenosis. Most people with mild to moderate aortic stenosis do not have symptoms. Symptoms usually are manifest in those with severe aortic stenosis, although they can exist in those with mild to moderate severity as well. The initial presenting symptoms include progressive shortness of breath on exertion, which may be so subtle that the the patient is unaware of them, and may cut down on exertion without being aware of his/her reduced capacity. More worrisome symptoms include syncope, chest pain, and frank heart failure.Congestive heart failure
Congestive heart failureCongestive 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...
(CHF) carries a grave prognosis in patients with AS. Patients with CHF that is attributed to AS have a 2 year mortality rate of 50%, if the aortic valve is not replaced.
CHF in the setting of AS is due to a combination of systolic dysfunction (a decrease in the ejection fraction
Ejection fraction
In cardiovascular physiology, ejection fraction is the fraction of Blood pumped out of the Right Ventricle of the heart to the Pulmonary Circulation and Left Ventricle of the heart to the Systemic Circulation with each Heart beat or Cardiac cycle...
) and diastolic dysfunction
Diastolic dysfunction
Diastolic heart failure or diastolic dysfunction refers to decline in performance of one or both ventricles of the heart during the time phase of diastole...
(elevated filling pressure of the LV).
Syncope
SyncopeSyncope
In phonology, syncope is the loss of one or more sounds from the interior of a word; especially, the loss of an unstressed vowel. It is found bothin Synchronic analysis of languages and Diachronics .-Found synchronically:...
(fainting spells) from aortic valve stenosis is usually exertional. In the setting of heart failure it increases the risk of death. In patients with syncope, the 3 year mortality rate is 50%, if the aortic valve is not replaced.
It is unclear why aortic stenosis causes syncope. One popular theory is that severe AS produces a nearly fixed 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...
. When the patient exercises, their peripheral vascular resistance will decrease as the blood vessels of the skeletal muscles dilate to allow the muscles to receive more blood to allow them to do more work. This decrease in peripheral vascular resistance is normally compensated for by an increase in the cardiac output. Since patients with severe AS cannot increase their cardiac output, the blood pressure falls and the patient will syncopize due to decreased blood perfusion to the brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
.
A second theory as to why syncope may occur in AS is that during exercise, the high pressures generated in the hypertrophied LV cause a vasodepressor response, which causes a secondary peripheral vasodilation
Vasodilation
Vasodilation refers to the widening of blood vessels resulting from relaxation of smooth muscle cells within the vessel walls, particularly in the large arteries, smaller arterioles and large veins. The process is essentially the opposite of vasoconstriction, or the narrowing of blood vessels. When...
that, in turn, causes decreased blood flow to the brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
. Indeed, in aortic stenosis, because of the fixed obstruction to bloodflow out from the heart, it may be impossible for the heart to increase its output to offset peripheral vasodilation.
A third mechanism may sometimes be operative. Due to the hypertrophy of the left ventricle
Left ventricle
The left ventricle is one of four chambers in the human heart. It receives oxygenated blood from the left atrium via the mitral valve, and pumps it into the aorta via the aortic valve.-Shape:...
in aortic stenosis, including the consequent inability of the coronary arteries to adequately supply blood to the myocardium (see "Angina" below), arrhythmias may develop. These can lead to 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...
.
Finally, in calcific aortic stenosis at least, the calcification in and around the aortic valve can progress and extend to involve the 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...
. If that occurs, the result may be heart block
Heart block
A heart block can be a blockage at any level of the electrical conduction system of the heart .* Blocks that occur within the sinoatrial node are described as SA nodal blocks....
- a potentially lethal condition of which syncope may be a symptom.
Angina
Angina in the setting of heart failure also increases the risk of death. In patients with angina, the 5 year mortality rate is 50%, if the aortic valve is not replaced.Angina in the setting of AS is secondary to the left ventricular hypertrophy
Left ventricular hypertrophy
Left ventricular hypertrophy is the thickening of the myocardium of the left ventricle of the heart.-Causes:While ventricular hypertrophy occurs naturally as a reaction to aerobic exercise and strength training, it is most frequently referred to as a pathological reaction to cardiovascular...
(LVH) that is caused by the constant production of increased pressure required to overcome the pressure gradient caused by the AS. While the myocardium (i.e., heart muscle) of the LV gets thicker, the arteries that supply the muscle do not get significantly longer or bigger, so the muscle may become ischemic (i.e., does not receive an adequate blood supply). The 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...
may first be evident during exercise, when the heart muscle requires increased blood supply to compensate for the increased workload. The individual may complain of exertional angina. At this stage, a stress test
Stress test
Stress test may refer to:*Stress Test , an episode of Brandy and Mr Whiskers*Stress testing, a form of testing that is used to determine the stability of a given system or entity*Stress testing , determines the robustness of software...
with imaging may be suggestive of ischemia.
Eventually, however, the muscle will require more blood supply at rest than can be supplied by the coronary artery branches. At this point there may be signs of ventricular strain pattern (ST segment depression and T wave inversion) on the EKG, suggesting subendocardial ischemia. The subendocardium is the region that becomes ischemic because it is the most distant from the epicardial coronary arteries.
Associated symptoms
In Heyde's syndromeHeyde's syndrome
Heyde's syndrome is a syndrome of aortic valve stenosis associated with gastrointestinal bleeding from colonic angiodysplasia. It is named after Dr. Edward C. Heyde, who first described the association in 1958...
, aortic stenosis is associated with angiodysplasia
Angiodysplasia
In medicine , angiodysplasia is a small vascular malformation of the gut. It is a common cause of otherwise unexplained gastrointestinal bleeding and anemia. Lesions are often multiple, and frequently involve the cecum or ascending colon, although they can occur at other places...
of the colon
Colon (anatomy)
The colon is the last part of the digestive system in most vertebrates; it extracts water and salt from solid wastes before they are eliminated from the body, and is the site in which flora-aided fermentation of unabsorbed material occurs. Unlike the small intestine, the colon does not play a...
. Recent research has shown that the stenosis causes a form of von Willebrand disease
Von Willebrand disease
von Willebrand disease is the most common hereditary coagulation abnormality described in humans, although it can also be acquired as a result of other medical conditions. It arises from a qualitative or quantitative deficiency of von Willebrand factor , a multimeric protein that is required for...
by breaking down its associated 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...
factor (factor VIII
Factor VIII
Factor VIII is an essential blood clotting factor also known as anti-hemophilic factor . In humans, Factor VIII is encoded by the F8 gene...
-associated antigen, also called von Willebrand factor
Von Willebrand factor
von Willebrand factor is a blood glycoprotein involved in hemostasis. It is deficient or defective in von Willebrand disease and is involved in a large number of other diseases, including thrombotic thrombocytopenic purpura, Heyde's syndrome, and possibly hemolytic-uremic syndrome...
), due to increased turbulence around the stenosed valve.
Physical examination
Aortic stenosis is most often diagnosed when it is asymptomaticAsymptomatic
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...
and can sometimes be detected during routine examination of the heart and circulatory system. Good evidence exists to demonstrate that certain characteristics of the peripheral pulse can rule in the diagnosis. In particular, there may be a slow and/or sustained upstroke of the arterial pulse, and the pulse may be of low volume. This is sometimes referred to as pulsus parvus et tardus. There may also be a noticeable delay between the first heart sound
Heart sounds
Heart sounds, or heartbeats, are the noises generated by the beating heart and the resultant flow of blood through it...
(on auscultation
Auscultation
Auscultation is the term for listening to the internal sounds of the body, usually using a stethoscope...
) and the corresponding pulse in the carotid artery (so-called 'apical-carotid delay'). In similar manner, there may be a delay between the appearance of each pulse in the brachial artery (in the arm) and the radial artery (in the wrist).
The first heart sound may be followed by a sharp ejection sound ("ejection click") best heard at the lower left sternal border and the apex, and, thus, appear to be "split". The ejection sound, caused by the impact of left ventricular outflow against the partially fused aortic valve leaflets, is more commonly associated with a mobile bicuspid aortic valve
Bicuspid aortic valve
A bicuspid aortic valve is most commonly a congenital condition of the aortic valve where two of the aortic valvular leaflets fuse during development resulting in a valve that is bicuspid instead of the normal tricuspid configuration. Normally the only cardiac valve that is bicuspid is the mitral...
than an immobile calcified aortic valve. The intensity of this sound does not vary with respiration, which helps distinguish it from the ejection click produced by a stenotic pulmonary valve, which will diminish slightly in intensity during inspiration.
An easily heard systolic
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...
, crescendo-decrescendo (i.e., 'ejection') murmur
Heart murmur
Murmurs are extra heart sounds that are produced as a result of turbulent blood flow that is sufficient to produce audible noise. Most murmurs can only be heard with the assistance of a stethoscope ....
is heard loudest at the upper right sternal border, at the 2nd right intercostal space, and radiates to the carotid arteries
Carotid artery
Carotid artery can refer to:* Common carotid artery* External carotid artery* Internal carotid artery...
bilaterally. The murmur increases with squatting, decreases with standing and isometric muscular contraction, which helps distinguish it from hypertrophic obstructive cardiomyopathy (HOCM). The murmur is louder during expiration, but is also easily heard during inspiration. The more severe the degree of the stenosis, the later the peak occurs in the crescendo-decrescendo of the murmur.
The second heart sound (A2) tends to become decreased and softer as the aortic stenosis becomes more severe. This is a result of the increasing calcification of the valve preventing it from "snapping" shut and producing a sharp, loud sound. Due to increases in left ventricular pressure from the stenotic aortic valve, over time the ventricle may hypertrophy, resulting in a diastolic dysfunction. As a result, one may hear a fourth heart sound
Fourth heart sound
The fourth heart sound or S4 is a rare extra heart sound that occurs immediately before the normal two "lub-dub" heart sounds . It occurs just after atrial contraction and immediately before the systolic S1...
due to the stiff ventricle. With continued increases in ventricular pressure, dilatation of the ventricle will occur, and a third heart sound may be manifest.
Finally, aortic stenosis often co-exists with some degree of aortic insufficiency
Aortic insufficiency
Aortic insufficiency , also known as aortic regurgitation , is the leaking of the aortic valve of the heart that causes blood to flow in the reverse direction during ventricular diastole, from the aorta into the left ventricle....
(aortic regurgitation). Hence, the physical exam in aortic stenosis may also reveal signs of the latter, for example an early diastolic decrescendo murmur. Indeed, when both valve abnormalities are present, the expected findings of either may be modified or may not even be present. Rather, new signs that reflect the presence of simultaneous aortic stenosis and insufficiency, e.g., pulsus bisferiens
Pulsus bisferiens
In medicine, pulsus bisferiens, also bisferious pulse or biphasic pulse, is a sign where, on palpation of the pulse, a double peak per cardiac cycle can be appreciated. Bisferious means striking twice...
, emerge.
According to a meta analysis, the most useful findings for ruling in aortic stenosis in the clinical setting were slow rate of rise of the carotid pulse(positive likelihood ratio
Likelihood ratios in diagnostic testing
In evidence-based medicine, likelihood ratios are used for assessing the value of performing a diagnostic test. They use the sensitivity and specificity of the test to determine whether a test result usefully changes the probability that a condition exists.-Calculation:Two versions of the...
ranged 2.8–130 across studies), mid to late peak intensity of the murmur(positive likelihood ratio, 8.0–101), and decreased intensity of the second heart sound (positive likelihood ratio, 3.1–50).
Other peripheral signs include:
- sustained, heaving apex beatApex beatThe apex beat, also called the point of maximum impulse , is the furthermost point outwards and downwards from the sternum at which the cardiac impulse can be felt...
, which is not displaced unless systolic dysfunction of the left ventricular has developed - A precordial thrill
- narrowed pulse pressure
The electrocardiogram (ECG)
Although aortic stenosis does not lead to any specific findings on the ECG, it still often leads to a number of electrocardiographic abnormalities. ECG manifestations of left ventricular hypertrophyLeft ventricular hypertrophy
Left ventricular hypertrophy is the thickening of the myocardium of the left ventricle of the heart.-Causes:While ventricular hypertrophy occurs naturally as a reaction to aerobic exercise and strength training, it is most frequently referred to as a pathological reaction to cardiovascular...
(LVH) are common in aortic stenosis and arise as a result of the stenosis having placed a chronically high pressure load on the left ventricle
Left ventricle
The left ventricle is one of four chambers in the human heart. It receives oxygenated blood from the left atrium via the mitral valve, and pumps it into the aorta via the aortic valve.-Shape:...
(with LVH being the expected response to chronic pressure loads on the left ventricle no matter what the cause).
As noted above, the calcification process that occurs in aortic stenosis can progress to extend beyond the aortic valve and into the 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...
. Evidence of this phenomenon may include heart block
Heart block
A heart block can be a blockage at any level of the electrical conduction system of the heart .* Blocks that occur within the sinoatrial node are described as SA nodal blocks....
that is apparent on the ECG but otherwise undetectable.
Heart catheterization
Cardiac chamber catheterization provides a definitive diagnosis, indicating severe stenosis in valve area of <0.8 cm2 (normally 1.5 to 2 cm2). It can directly measure the pressure on both sides of the aortic valve. The pressure gradient may be used as a decision point for treatment. It is useful in symptomatic patients before surgery.Echocardiogram
| Severity of aortic stenosis | ||
|---|---|---|
| Degree of aortic stenosis | Mean gradient (mmHg) | Aortic valve area (cm2) |
| Mild aortic stenosis | <25 | >1.5 |
| Moderate aortic stenosis | 25 - 40 | 1.0 - 1.5 |
| Severe aortic stenosis | >40 | < 1.0 |
| Critical aortic stenosis | >70 | < 0.6 |
Echocardiogram (heart ultrasound) is the best non-invasive test to evaluate the aortic valve anatomy and function.
The aortic valve area can be calculated
Aortic valve area calculation
Aortic valve area calculation is an indirect method of determining the area of the aortic valve. The calculated aortic valve orifice area is currently one of the measures for evaluating the severity of aortic stenosis. A valve area of less than 0.8 cm² is considered to be severe aortic...
non-invasively using echocardiographic flow velocities. Using the velocity of the blood through the valve, the pressure gradient across can be calculated by the modified Bernoulli's equation:
Gradient = 4(velocity)² mmHgA normal aortic valve has a gradient of only a few mmHg. A decreased valvular area causes increased pressure gradient, and these parameters are used to classify aortic stenosis as either mild, moderate or severe. The pressure gradient can be abnormally low in the presence of 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:...
, heart failure or co-existent aortic regurgitation.
Echocardiogram may also show left ventricular hyperthrophy, thickened and immobile aortic valve and dilated aortic root. However, it may appear deceptively normal in acute cases.
Chest X-ray
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...
can also assist in the diagnosis, showing calcific aortic valve, and, in longstanding disease, enlarged left ventricle and atrium.
Cautions
People with aortic stenosis of any aetiology are at risk for the development of infection of their stenosed valve, i.e., infective endocarditisInfective endocarditis
Infective endocarditis is a form of endocarditis, or inflammation, of the inner tissue of the heart, such as its valves, caused by infectious agents. The agents are usually bacterial, but other organisms can also be responsible....
. To lessen the chance of developing that serious complication, people with AS are usually advised to take antibiotic prophylaxis around the time of certain dental/medical/surgical procedures. Such procedures may include dental extraction, deep scaling of the teeth, gum surgery, dental implants, treatment of esophageal varices
Esophageal varices
In medicine , esophageal varices are extremely dilated sub-mucosal veins in the lower esophagus...
, dilation of esophageal stricture
Esophageal stricture
Benign esophageal stricture is a narrowing or tightening of the esophagus that causes swallowing difficulties.-Causes:It can be caused by or associated with gastroesophageal reflux disease, esophagitis , dysfunctional lower esophageal sphincter, disordered motility, lye ingestion, or a hiatal hernia...
s, gastrointestinal surgery where the intestinal mucosa will be disrupted, prostate
Prostate
The prostate is a compound tubuloalveolar exocrine gland of the male reproductive system in most mammals....
surgery, urethral stricture
Urethral stricture
A urethral stricture is a narrowing of the urethra caused by injury or disease such as urinary tract infections or other forms of urethritis.-Signs and symptoms:...
dilation, and cystoscopy
Cystoscopy
Cystoscopy is endoscopy of the urinary bladder via the urethra. It is carried out with a cystoscope.Diagnostic cystoscopy is usually carried out with local anaesthesia...
. Note that routine upper and lower GI endoscopy
Endoscopy
Endoscopy means looking inside and typically refers to looking inside the body for medical reasons using an endoscope , an instrument used to examine the interior of a hollow organ or cavity of the body. Unlike most other medical imaging devices, endoscopes are inserted directly into the organ...
(i.e., gastroscopy and colonoscopy
Colonoscopy
Colonoscopy is the endoscopic examination of the large bowel and the distal part of the small bowel with a CCD camera or a fiber optic camera on a flexible tube passed through the anus. It may provide a visual diagnosis and grants the opportunity for biopsy or removal of suspected...
), with or without biopsy
Biopsy
A biopsy is a medical test involving sampling of cells or tissues for examination. It is the medical removal of tissue from a living subject to determine the presence or extent of a disease. The tissue is generally examined under a microscope by a pathologist, and can also be analyzed chemically...
, are not usually considered indications for antibiotic prophylaxis.
Notwithstanding the foregoing, the American Heart Association has recently changed its recommendations regarding antibiotic prophylaxis for endocarditis. Specifically, as of 2007, it is recommended that such prophylaxis be limited only to 1. those with prosthetic heart valves, 2. those with previous episode(s) of endocarditis, and 3. those with certain types of congenital heart disease.[Dead Link]
Since the stenosed aortic valve may limit the heart's output, people with aortic stenosis are at risk of 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...
and dangerously low blood pressure should they use any of a number of medications for cardiovascular diseases that often co-exist with aortic stenosis. Examples include nitroglycerin, nitrates, ACE inhibitor
ACE inhibitor
ACE inhibitors or angiotensin-converting enzyme inhibitors are a group of drugs used primarily for the treatment of hypertension and congestive heart failure...
s, terazosin
Terazosin
Terazosin is a selective alpha 1 antagonist used for treatment of symptoms of an enlarged prostate...
(Hytrin), and hydralazine
Hydralazine
Hydralazine is a direct-acting smooth muscle relaxant used to treat hypertension by acting as a vasodilator primarily in arteries and arterioles...
. Note that all of these substances lead to peripheral vasodilation
Vasodilation
Vasodilation refers to the widening of blood vessels resulting from relaxation of smooth muscle cells within the vessel walls, particularly in the large arteries, smaller arterioles and large veins. The process is essentially the opposite of vasoconstriction, or the narrowing of blood vessels. When...
. Under normal circumstances, in the absence of aortic stenosis, the heart is able to increase its output and thereby offset the effect of the dilated blood vessels. In some cases of aortic stenosis, however, due to the obstruction of blood flow out of the heart caused by the stenosed aortic valve, 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...
cannot be increased. Low blood pressure or 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...
may ensue.
Neonatal
The above is entirely about adult aortic stenosis. In the new born, abnormalities of the left ventricle, the aortic valve or other heart and aortic abnomalities may lead the Ductus Ateriosus remaining open, or the Duct may remain open with no other abnormality. See Patent Ductus Arteriosus (PDA) Patent ductus arteriosusPatent ductus arteriosus
Patent ductus arteriosus is a congenital disorder in the heart wherein a neonate's ductus arteriosus fails to close after birth. Early symptoms are uncommon, but in the first year of life include increased work of breathing and poor weight gain...
Then, and only then, in neonates, will the following advice be appropriate.
1.Stabilize with prostaglandin E1(PGE) infusion to maintain cardiac output through PDA.
2. Inotropic support as needed.
There is no medical treatment for aortic stenosis. Symptoms need assessment for surgery, severe symptoms may need urgent surgery. Meanwhile, dysrythmias or hypercholesterolaemia may need medical treatment.
Treatment
Treatment is generally not necessary in asymptomatic patients. In moderate cases, echocardiography is performed every 1–2 years to monitor the progression, possibly complemented with a cardiac 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....
. In severe cases, echocardiography is performed every 3–6 months. In both moderate and mild cases, the patient should immediately make a revisit or be admitted for inpatient care if any new related symptoms appear.
Aortic valve replacement
In adults, symptomatic aortic stenosis usually requires aortic valve replacementAortic valve replacement
Aortic valve replacement is a cardiac surgery procedure in which a patient's failing aortic valve is replaced with an alternate healthy valve. The aortic valve can be affected by a range of diseases; the valve can either become leaky or partially blocked...
(AVR). AVR has been the standard of care for aortic stenosis for several decades.
Apicoaortic Conduit
Apicoaortic ConduitApicoaortic Conduit
-Introduction:Apicoaortic Conduit , also known as Aortic Valve Bypass , is a cardiothoracic surgical procedure that alleviates symptoms caused by blood flow obstruction from the left ventricle of the heart. Left ventricular outflow tract obstruction is caused by narrowing of the aortic valve and...
(AAC), or Aortic Valve Bypass (AVB), has been shown to be an effective treatment for aortic stenosis. There is long-term stability of the left ventricular hemodynamics
Hemodynamics
Hemodynamics, meaning literally "blood movement" is the study of blood flow or the circulation.All animal cells require oxygen for the conversion of carbohydrates, fats and proteins into carbon dioxide , water and energy in a process known as aerobic respiration...
after AVB, with no further biologic progression of native aortic valve stenosis. Once the pressure gradient across the native valve is substantially reduced, the narrowing and calcification of the native valve halts.
Percutaneous Aortic Valve Replacement
According to a prospective, single-center, nonrandomized study of 25 patients, percutaneousPercutaneous
In surgery, percutaneous pertains to any medical procedure where access to inner organs or other tissue is done via needle-puncture of the skin, rather than by using an "open" approach where inner organs or tissue are exposed .The percutaneous approach is commonly used in vascular procedures...
implantation of an aortic valve prosthesis
Artificial heart valve
An artificial heart valve is a device implanted in the heart of a patient with heart valvular disease. When one of the four heart valves malfunctions, the medical choice may be to replace the natural valve with an artificial valve. This requires open-heart surgery.Valves are integral to the normal...
in high-risk patients with aortic stenosis results in marked hemodynamic and clinical improvement when successfully completed. Medium- and long-term results are unknown. When selecting the optimal therapy for individual patients, the percutaneous approach must be carefully weighed against the excellent results achieved with conventional surgery.
Balloon valvuloplasty
For infants and children, balloon valvuloplasty, where a balloon is inflated to stretch the valve and allow greater flow, may also be effective. In adults, however, it is generally ineffective, as the valve tends to return to a stenosed state. The surgeon will make a small incision at the top of the patient's leg and proceed to insert the balloon into the artery and then inflate it to get a better flow of blood around the patient's body.Medical
In general, any medical therapy has relatively poor effect in treating aortic stenosis. It is useful, however, in management of concomitant conditions that correlate with aortic stenosis:- Any angina is generally treated with beta-blockers and/or calcium blockers. Nitrates are contraindicated due to their potential to cause profound hypotensionHypotensionIn 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...
in aortic stenosis. - Any 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...
is treated aggressively, but caution must be taken in administering beta-blockers - Any heart failure is generally treated with 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...
and diureticDiureticA diuretic provides a means of forced diuresis which elevates the rate of urination. There are several categories of diuretics. All diuretics increase the excretion of water from bodies, although each class does so in a distinct way.- Medical uses :...
s, and, if not contraindicated, cautious inpatient administration of ACE inhibitorACE inhibitorACE inhibitors or angiotensin-converting enzyme inhibitors are a group of drugs used primarily for the treatment of hypertension and congestive heart failure...
s. As for angina, nitrates are contraindicated.
Since calcific aortic stenosis shares many pathological features and risk factors with atherosclerosis
Atherosclerosis
Atherosclerosis is a condition in which an artery wall thickens as a result of the accumulation of fatty materials such as cholesterol...
, and since atherosclerosis may be prevented and/or reversed by cholesterol lowering, there has been interest in attempting to modify the course of calcific aortic stenosis by cholesterol lowering with statin
Statin
Statins are a class of drugs used to lower cholesterol levels by inhibiting the enzyme HMG-CoA reductase, which plays a central role in the production of cholesterol in the liver. Increased cholesterol levels have been associated with cardiovascular diseases, and statins are therefore used in the...
drugs. Although a number of small, observational studies demonstrated an association between lowered cholesterol and decreased progression, and even regression, of calcific aortic stenosis, a recent, large randomized clinical trial, published in 2005, failed to find any predictable effect of cholesterol lowering on calcific aortic stenosis. A 2007 study did demonstrate a slowing of aortic stenosis with the statin rosuvastatin
Rosuvastatin
Rosuvastatin is a member of the drug class of statins, used to treat high cholesterol and related conditions, and to prevent cardiovascular disease. It was developed by Shionogi.-Medical uses:The primary uses of rosuvastatin is for the treatment of dyslipidemia...
. However, what is likely to be considered the definitive trial, published in the New England Journal of Medicine in 2008, failed to find any beneficial effect of intensive cholesterol lowering on the course of aortic stenosis.