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Heart Valve Disease Heart valve disease. A heart valve is a structure at the exit of a heart chamber, consisting of two or three cup shaped flaps, that allows blood to flow out of the chamber but prevents it from washing back. There are four heart valves: aortic, pulmonary, mitral, and tricuspid. The opening and closing of the heart valves during each heart cycle produces heart sounds which can be heard with a stethoscope.
Disorders of heart valves Heart valves may be affected by stenosis (narrowing), in which the heart must work harder to force blood through, or by incompetence or insufficiency (leakiness), which makes the valve unable to prevent regurgitation (backwash) of blood. These defects cause heart murmurs. Defects of the heart valves may be present from birth or acquired later in life. The most common congenital valve defects are aortic stenosis and pulmonary stenosis. Acquired heart-valve disease is usually the result of degenerative changes or ischaemia (reduced blood supply) affecting part of the heart and leading to aortic stenosis or mitral incompetence. Rheumatic fever can cause mitral stenosis, mitral incompetence, defects of the aortic valve, tricuspid stenosis, and tricuspid incompetence. Heart valves may also be damaged by bacterial endocarditis. Heart-valve disorders commonly lead to heart failure, arrhythmias, or symptoms that arise from reduced blood supply to the tissues. echocardiography (http://www.emedmd.com/content/echocardiography) and may be corrected
Heart-valve defects may be diagnosed by auscultation, chest X-ray, ECG, or by heart-valve surgery.
Heart-valve surgery This is an operation to correct a heart valve defect or to remove a diseased or damaged valve. A heart valve may have to be repaired, widened, or replaced because it is either incompetent (leaky), stenotic (narrowed), or both. Widening of a valve may involve valvotomy or valvuloplasty. A damaged valve can be replaced by a mechanical one (fashioned from metal and plastic), a valve constructed from human tissue, a pig valve, or a valve taken from a human donor after death. A heart– lung machine is used during valve replacement. After heart-valve surgery, there may be symptoms of breathlessness for several weeks that require continued medication. Some people require long-term treatment with anticoagulant drugs to prevent the formation of blood clots around the new valve. Certain types of replacement valve, such as mechanical valves, are more likely to cause clots than other types.
Heart valve disease in detail - technical Topics covered: Essentials Introduction The mitral valve Aortic valve disease Right heart valve disease Further reading
Essentials Rheumatic valve disease remains prevalent in developing countries, but over the last 50 years there has been a decline in the incidence of rheumatic valve disease and an increase in the prevalence of degenerative valve pathology in northern Europe and North America. In all forms of valve disease, the most appropriate initial diagnostic investigation is almost always the echocardiogram. Mitral stenosis The most common cause is rheumatic valve disease. Other causes include mitral annular calcification, congenital mitral stenosis, infective endocarditis (very rarely), and systemic lupus erythematosus (SLE) (Liebman–Sachs endocarditis). The important consequences of mitral stenosis are its effect on left atrial pressure, size, and the pulmonary vasculature; it commonly causes atrial fibrillation. Presenting symptoms are typically exertional fatigue and breathlessness; systemic embolism can occur. Characteristic physical signs are irregular pulse, tapping apex beat, loud first heart sound, opening snap, and an apical low-pitched rumbling mid-diastolic murmur. Management—the only medical treatments in mitral stenosis are (1) prophylactic measures against rheumatic fever and endocarditis; (2) anticoagulation to prevent systemic embolism; and (3) diuretics for raised left atrial pressure. Patients who are symptomatic need intervention by either surgical valvotomy or catheter–balloon valvuloplasty, whether or not they have pulmonary hypertension. Early intervention—before the development of atrial fibrillation and an enlarged left atrium—is recommended, provided a conservative operation is possible. Mitral valve replacement is reserved for cases where the mitral valve cannot be repaired. Mitral regurgitation The most common causes are ischaemic myocardial dysfunction, mitral valve prolapse, and dilated cardiomyopathy. Other causes include congenital valve disease, infective endocarditis, endomyocardial fibrosis, and connective tissue diseases (including Marfan’s syndrome). Mitral regurgitation is an isolated volume overload on the left ventricle, providing the physiological equivalent of afterload reduction so that a normal forward cardiac output is maintained by the combination of increased ejection fraction and higher preload. Patients with mild regurgitation may not have any symptoms: those with severe regurgitation are likely to present with dyspnoea. Characteristic physical signs are an apex beat that may be prominent and displaced, an apical pansystolic murmur, and a third heart sound. The loudness of the murmur generally correlates with severity of regurgitation. The cardinal signs of mitral prolapse are a midsystolic click followed by a murmur. Endocarditis prophylaxis may be recommended to high risk patients with regurgitation. Patients in atrial fibrillation should be given anticoagulants. The development of symptoms suggests the need for surgical correction to avoid development of irreversible left ventricular dysfunction. Assessment during routine follow-up should 2 being one proposed identify those likely to need surgical intervention even in the absence of symptoms, with an effective regurgitant orifice of over 40 mm indication. It is generally considered that a left ventricular end-systolic dimension more than 50 mm indicates a poor prognosis and that surgical intervention is unlikely to be of benefit. If technically possible, mitral valve repair results in a much better clinical outcome than does valve replacement, but mitral replacement by a mechanical valve or bioprosthesis is the only option for irreparable valves.
Aortic stenosis Aortic stenosis may be at subvalvar, valvar, or supravalvar level, the commonest being valvar stenosis. Age-related degenerative calcific disease is the commonest cause in western Europe and the United States of America. Other causes include congenital bicuspid aortic valve and rheumatic disease (always associated with aortic regurgitation, ‘mixed aortic valve disease’, and usually with rheumatic mitral disease). With the increase in outflow-tract resistance in aortic stenosis, left ventricular wall stress increases and hypertrophy develops, preserving overall ventricular systolic function, but potentially at the expense of subendocardial ischaemia. Patients with mild disease may be asymptomatic, and even severe stenosis may be silent, but breathlessness, angina, and syncope are typical. Characteristic physical signs are a slowly rising, low-amplitude pulse, a narrow pulse pressure, a sustained apex beat, and a long and harsh ejection systolic murmur that is loudest at the base (second right intercostal space, also known as the aortic area) of the heart, and in most cases radiates to the carotids (where a thrill may be palpable). Management—patients with moderate or severe disease should be advised to avoid strenuous exercise. Prophylaxis against endocarditis may be recommended to high risk patients. Asymptomatic patients with mild or moderate aortic stenosis require follow-up; those with severe disease (pressure gradient 70 mmHg) need aortic valve replacement. Aortic regurgitation Aortic regurgitation is caused by leaflet disease or aortic root dilatation, the commonest causes being isolated medionecrosis, rheumatic disease, infective endocarditis, and Marfan’s syndrome. The left ventricular stroke volume is significantly increased, which is accommodated by an increase in left ventricular cavity size. As disease progresses, end-systolic volume increases out of proportion to stroke volume, and eventually these changes lead to irreversible damage. The onset of symptoms, particularly breathlessness, coincides with the onset of left ventricular disease. Characteristic physical signs of chronic severe aortic regurgitation are a large amplitude ‘collapsing’ pulse (which when severe can induce pulsations in many parts of the body), a low diastolic blood pressure (80 mmHg), an apex beat that is sustained and/or displaced, and an early diastolic, decrescendo murmur, loudest at the left sternal border. Acute aortic regurgitation causes the patient to be cold and shut down, with tachycardia, hypotension, and a short early diastolic murmur that is easily missed. Management—medical treatment of chronic aortic regurgitation includes angiotensin converting enzyme (ACE) inhibitors and/or calcium channel blockers to reduce afterload. Patients with a dilated aortic root should be given -blockade with ACE inhibition/angiotensin receptor blockers. Prophylaxis against endocarditis may be recommended to high risk patients. Although patients with severe chronic aortic regurgitation may remain asymptomatic, valve replacement should be offered when there is progressive increase in left ventricular end systolic dimension, which should not be allowed to reach more than 40 mm. Right heart valve disease Many of the conditions that cause right-sided valve diseases are congenital, and are excluded from further discussion here (see: adult (http://www.emedmd.com/content/congenital-heart-disease-adult) ).
Congenital heart disease in the
Tricuspid stenosis—this is rare, but most often caused by rheumatic disease that almost invariably simultaneously affects the mitral valve. Symptoms include fatigue, dyspnoea, and fluid retention. On auscultation at the left or right sternal edge, a mid-diastolic murmur is heard and a tricuspid opening snap may be present. Diuretics can help to minimize fluid retention. Severe tricuspid stenosis needs surgical repair, or replacement if additional regurgitation is present. Tricuspid regurgitation —significant disease is most commonly secondary to pulmonary hypertension and/or right heart dilatation; the commonest noncongenital primary cause is infective endocarditis. Symptoms include fluid retention and hepatic congestion. A raised venous pressure with prominent V-wave is expected. Other signs include a pansystolic murmur at the left or right sternal edge (in one-third of cases), expansile pulsation of the liver (in most), and peripheral oedema/ascites. Diuretics and ACE inhibitors may reduce systemic venous pressure and right ventricular size, even restoring valve competence in some cases. Valve repair or replacement may be advised in some cases. Pulmonary stenosis—a rare condition usually caused by rheumatic disease or carcinoid syndrome. Fatigue and dyspnoea are the main symptoms. Characteristic physical signs are a prominent venous ‘a’ wave in the neck and an ejection systolic murmur loudest at the upper left sternal edge. Balloon valvuloplasty is the procedure of choice if intervention is warranted. Pulmonary regurgitation—significant disease is rare, but usually caused by rheumatic disease, carcinoid, and endocarditis. The characteristic physical sign is a soft early diastolic murmur in the left upper parasternal region. Arrhythmia or progressive right ventricular dilatation are indications for surgery, using homograft or conduit and valve.
Introduction Over the last 50 years there has been a significant shift in the causes of heart valve disease in Northern Europe and North America, with a decline in the incidence of rheumatic valve disease and an increase in the prevalence of degenerative valve pathology. Rheumatic valve disease remains prevalent in the developing countries, particularly in areas with limited clinical services. The commonest valve involved with rheumatic pathology is the mitral valve, but the aortic and tricuspid valves can also be involved. The apparent increase in the diagnosis of valve disease could be due either to ageing of the population or to the extensive use of echocardiography in cardiology clinics. Age affects the valves, making leaflets thicker with fibrous strands and adipose tissue deposition at the closure lines of the leaflets. Isolated myxomatous changes may also occur in the valve fibrosa. In patients with a suspected diagnosis of endocarditis these changes can add to diagnostic difficulty since they may look like small vegetations, and they also need to be distinguished from papillary muscle fibroelastoma. Medical treatment of valve disease is limited, focusing mostly on prophylaxis against endocarditis and ventricular dysfunction as well as optimizing haemodynamics. Although surgical repair is the main conventional treatment of severe valve disease, the need for this is 5 to 10 times less than that for coronary artery disease. Valve-related mortality is more common in aortic valve disease than mitral valve disease, largely due to the frequent development of left ventricular dysfunction that causes congestive heart failure. Other causes of death in valve disease are additional pathologies such as coronary artery disease, endocarditis, or arrhythmia.
The mitral valve Normal mitral valve anatomy and function Optimum function of the mitral valve depends on the intact function of all its components—leaflets, chordae, annulus, and papillary muscles, in addition to the left atrium and the left ventricle. A normal mitral valve does not close passively. In addition to the pressure difference between the ventricle and atrium in systole, the annular contraction and papillary muscle contraction play an important role in the competence of the mitral valve. The anterior mitral valve leaflet represents a continuation of the posterior aortic root wall. The annular fibrous ring is located mainly posteriorly; it is usually D- shaped but there is significant variability in different individuals. The normal diameter of the mitral annulus is around 3 cm with a circumference of 8 to 9 cm: it is not a passive structure, so in addition to its normal movement towards the apex in systole, the contraction of the posterior myocardial muscle shortens its diameter by 25%, with such movement being a very important component in the mechanism of mitral valve competence. Change in the size and shape of the left atrial cavity is a cause for incompetence of the mitral valve by enlarging the annular diameter. Loss of atrial mechanical function may contribute significantly to the development of mitral regurgitation in patients with atrial fibrillation. Likewise, atrial fibrillation itself has been shown to contribute to the enlargement of the left atrium and consequently the development of mitral regurgitation. The two leaflets of the mitral valve meet at the medial and lateral commissures. The area of the U-shaped anterior leaflet is larger than that of the posterior leaflet, which is wider and shorter than the anterior leaflet. The posterior leaflet is made up of a number of scallops, commonly three. The two leaflets coapt at the zone of apposition, leaving an overlapping segment 5 mm long. The chordal anatomy of the mitral valve is complicated, with around 12 primary chordae rising from each papillary muscle. These divide into secondaries and numerous tertiary branches that attach themselves to the margins of the two leaflets. In addition, a number of basal chordae also attach themselves to the ventricular surface of the leaflets and to the commissures. The location of the chordae follows that of the papillary muscles anterolaterally and posteromedially. Any rupture or redundancy of the chordae or extra tissue in the leaflets results in mitral regurgitation. Mitral stenosis Causes The most common cause of mitral stenosis, which affects women more than men (2:1), is rheumatic valve disease. The rheumatic process involves not only the leaflets but may also affect the chordae and the annulus, causing fibrosis and superimposed calcification. The rheumatic leaflets become thickened and fibrosed, and the commissures fuse. The end result of this pathology is a reduction in mitral valve area, the rigid movement of the leaflets and the commissural fusion together contributing to the limited flow across the mitral valve orifice and hence stenosis. It is not uncommon for the fibrotic process to involve the subvalvar region in an aggressive way, thus causing flow to be limited at the level of the subvalvar apparatus. In such cases the chordae become short and the inflow tract of the left ventricle become tunnel-like. Mitral annular calcification is another cause of raised filling velocities: this is seen in older people with the calcification limited to the annulus and the proximal segments of the leaflets, but the leaflets themselves are normal. A very uncommon cause of mitral stenosis is congenital mitral stenosis, which may be associated with other cardiac abnormalities. Infective endocarditis with bulky vegetations may rarely cause restriction of mitral flow, and patients with systemic lupus erythematosus (SLE) can develop fibrosis of the mitral cusps with commissural fusion following Liebman–Sachs endocarditis. Pathophysiology and complications The important consequence of mitral stenosis is its effect on left atrial pressure and size and on the pulmonary vasculature. As the valve area falls progressively, left atrial pressure rises, its size increases, and the pulmonary venous pressure also increases. In most patients with rheumatic mitral valve disease the left ventricle is normal in size and systolic function unless the valve stenosis is severe and making the ventricle under filled. With a mild degree of mitral stenosis, reduced orifice area is compensated by increased flow during atrial systole. As the valve stenosis becomes more severe, the left atrial pressure increases, the pressure difference between the atrium and the ventricle increases, and the filling occurs throughout diastole. In severe mitral stenosis the pressure difference may be as high as 25 to 30 mmHg. Long-standing disease may result in irreversible pulmonary hypertension secondary to the raised left atrial pressure. Atrial fibrillation also develops, with loss of mechanical atrial function. 2. Effective mitral valve A normal mitral valve area is of the order of 5 cm 2, compared to a valve area in a patient with severe mitral stenosis of less than 1 cm area changes very little with increase in heart rate compared to aortic valve area (which increases), the reason probably being the smaller number of commissures that assist opening of the mitral valve compared to the aortic valve. During exercise, particularly in atrial fibrillation, diastolic time falls and the fixed valve area causes raised left atrial pressure and pulmonary venous pressure.
Left atrial dilatation Progressive reduction in mitral valve orifice area causes progressive increase in left atrial pressure and size and pulmonary venous pressure. Left atrial dilatation is associated with reduction in its mechanical function that slows down intra-atrial blood circulation (swirling). With progressive disease and development of atrial fibrillation, the circulation in the atrium becomes very sluggish and echocardiography may demonstrate spontaneous echo-contrast, particularly on transoesophageal images. Such patients are given anticoagulants in order to avoid clot formation and hence the risk of transient ischaemic attacks (TIA). Almost one-fifth of the patients undergoing surgery for mitral stenosis have left atrial thrombus, and in one-third of them the thrombus is restricted to the atrial appendage. Atrial fibrillation This is the most common complication of mitral stenosis and its prevalence increases with age, being found in 70% of patients in their thirties and in 80% of those in their fifties. The presence of pulmonary hypertension raises the prevalence of atrial fibrillation. The Framingham study estimated a 20-fold increase in risk of stroke in patients with atrial fibrillation and mitral stenosis compared to only 5-fold increase in those without mitral valve disease. Left atrial thrombus may also form in patients with a dilated left atrium with spontaneous echo-contrast who are in sinus rhythm. The loss of left atrial appendage mechanical function has been proposed as a possible mechanism behind blood stagnation and thrombus formation. Left ventricular dysfunction
Although in most cases of mitral stenosis the left ventricle is normal in size and systolic function, in some diastolic function may be impaired and end-diastolic pressure raised. This could be related to additional pathology, e.g. systemic hypertension and diabetes. The left ventricle is dilated only in the presence of additional coronary artery disease. Primary rheumatic myocardial disease was proposed years ago, but no convincing evidence has ever come to light. Pulmonary hypertension With the increase in left atrial pressure, the pulmonary venous pressure increases and hence pulmonary arterial pressure also rises. Although pulmonary artery pressure corresponds to the degree of increase in left atrial pressure, a discrepancy between the two may reflect a raised pulmonary vascular resistance. A normal pressure drop across the pulmonary bed is of the order of 10–15 mmHg. The pulmonary hypertension is not always reversible after valve surgery. For any degree of mitral stenosis patients can display a wide range of pulmonary pressures, but it is very rare for secondary pulmonary hypertension to develop with left atrial pressure