Valvular Heart Disease and Its Prognosis | Medical Science

Heart Disease Mitral valve disease is the commonest form of chronic rheumatic valve disease, the valve being affected m about 85 per cent of cases. The affected valve may be either stenosed offering obstruction to the flow of blood from the left atrium to the left ventricle or the valve may be incompetent resulting in regurgitation of blood from the left ventricle to the left atrium during ventricular systole. Mitral stenosis with some degree of incompetence is however very common.

Mitral Stenosis:

There is usually a period of silent interval between the onset of rheumatic fever and the appearance of the signs and symptoms of mitral stenosis as the valve gradually narrows. Although in western countries, signs of mitral stenosis become apparent in the twenties and disability appears in late thirties or forties, however, juvenile mitral stenosis is fairly common in India, and the Middle East.

Aetiology:

The commonest cause of mitral stenosis is chronic rheumatic valvulitis; although a definite history of rheumatic fever may not be available in about 50 per cent of cases. Viral and rickettsial infection has rarely been incriminated. Congenital mitral stenosis is a rare entity and is often associated with coarctation of aorta or endocardial fibroelastosis. The association of mitral stenosis and ostium secundum type of atrial septal defect is referred to as Lutembacher’s syndrome, but the mitral valve lesion is almost invariably of rheumatic aetiology.

Pathology:

As a result of rheumatic endocarditis, there is thickening of valve leaflets, fusion of the chordae tendinae and fusion of the commissures. The end result is a funnel shaped deformity with a button-hole shaped orifice, of the valve. The normal mitral valve which has an area of about 4.5 cm² is gradually reduced. Symptoms appear when the valve area is reduced to 2.5 cm² although signs may be discernible much earlier. When the valve area is reduced to less than 1 cm², the narrowing is said to be critical.

The left ventricle is usually normal or small in size in isolated mitral stenosis. The left atrium is characteristically enlarged. The wall of the left atrium is histologically normal or there may be disruption of muscle fibres. Mural thrombosis may be seen in the free wall just above the posterior leaflet. This is known as McCallum’s patch. In the lungs one may notice changes of pulmonary venous congestion, pulmonary hypertension. Pulmonary haemosiderosis may develop in very late stage of the disease. The right ventricle dilates and there may be dilatation of the tricuspid valve ring.

Congenital mitral stenosis may take the form of a parachute valve or there may be commissural fusion like that seen in rheumatic mitral stenosis. The abnormal insertion of the chordae into a single papillary muscle produces the parachute valve.

Haemodynamics:

The underlying defect in mitral stenosis is obstruction to the flow of blood from the left atrium to left ventricle during diastole, resulting in a rise of pressure proximal to the obstruction. There is rise of pressure in the left atrium which dilates. The extent to which the left atrium dilates depends on its internal pressure and the state of atrial myocardium.

As the pressure in the left atrium rises there is consequent rise of pressure in the pulmonary veins. In order to maintain blood flow through the lungs, pulmonary arterial pressure starts rising in a linear relationship initially but this relationship is no longer maintained after some time and pulmonary arterial pressure rises rapidly due to arteriolar constriction — (Vasoconstrictive or active pulmonary hypertension).

The left atrial pressure in health does not exceed 12 mm Hg. In mitral stenosis the left atrial pressure progressively increases. A rise of pressure in left atrium is a good evidence of the mitral valve obstruction, but the only certain method of determining obstruction at the level of mitral valve is to estimate the diastolic pressure gradient across it by simultaneous measurement of left atrial and left ventricular pressure (Oram).

The smaller the valve area, the higher will be the pulmonary venous pressure and consequently higher will be pulmonary vascular resistance and lower will be the cardiac output. In mitral stenosis, blood flows normally from the left ventricle to the aorta, but during diastole a pressure gradient exists between left atrium and left ventricle due to continuing effort of the left atrium to force blood through the narrow mitral valve producing a turbulence during diastole.

Clinical Features:

Dyspnoea is the commonest presenting symptom in patients with mitral stenosis. Shortness of breath on exertion is complained of by about 80 per cent of patients. The dyspnoea is due to pulmonary congestion resulting from elevated left atrial pressure. The increased stiffness or decreased compliance of the lungs increases the work of breathing. Any factor that increases the heart rate is likely to aggravate dyspnoea in mitral stenosis.

Acute pulmonary oedema may be precipitated by emotion, infection, physical exertion, pregnancy, atrial fibrillation and anaesthesia. Anaemia and thyrotoxicosis are also likely to precipitate acute pulmonary oedema.

Paroxysmal nocturnal dyspnoea is not uncommon. A patient who usually complains of shortness of breath on exertion may go to bed in his usual state of health. After about an hour or two he gets up from sleep with an intense sense of suffocation accompanied by cough. He sits up or tries to proceed to go near an open window in an attempt to get some relief. The dyspnoea intensifies and he brings up pink frothy sputum.

Haemoptysis is an important presenting symptom if carefully enquired of. It may be the result of frank pulmonary haemorrhage from rupture of pulmonary veins. Pink frothy blood stained sputum may occur during an attack of acute pulmonary oedema. Infarction of lung is another cause for haemoptysis. Bronchitis in patients with mitral stenosis may cause blood screaking of the sputum.

Recurrent Bronchitis:

Bronchitis often associated with wheeze results from mucosal oedema caused by congestion in the bronchial veins which drain into pulmonary venous system.

Embolism:

Both systemic and pulmonary embolism may occur. Systemic embolism is more common in patients with atrial fibrillation. A fifth of the patients with mitral stenosis develop this complication sometimes during their lives. Hemiplegia or loss of use of a leg is recognised complications of systemic embolism. An unexplained incidence of epilepsy or hypertension in patients with mitral stenosis has been attributed to cerebral or renal infarction (Stevens).

Palpitation:

It is rare in pure mitral stenosis unless atrial fibrillation is present.

Symptoms due to raised pulmonary vascular resistance include fatigue, angina pectoris, and coldness of the extremities. Abdominal discomfort, anorexia, swelling of the ankles and feet become the presenting features when right heart failure sets in.

Fatigue:

Results from low cardiac output and is sometimes the presenting feature.

Angina results from low cardiac output in patients with raised pulmonary vascular resistance. As dyspnoea is the dominant symptom in mitral stenosis, a history of angina may not be obtained unless carefully sought.

Physical Signs:

The physical signs vary with the degree of severity of lesion and also on the amount of increase in pulmonary vascular resistance.

General appearance of the patient is unremarkable. The so-called “mitral facies” is not so
common in our patients. It is classically seen in white people when there is severe pulmonary hypertension and low cardiac output. The characteristic physical signs of mitral stenosis may appear much earlier than symptoms. The physical signs are often so insignificant that mild exercise is necessary to elicit signs. Patient is told to sit up and down from the lying posture for about 8 to 10 times and careful auscultation is done in left lateral posture.

Pulse:

In a classical case the pulse is usually normal but may have small volume. Atrial fibrillation is common.

The jugular venous pulse is usually normal but a prominent ‘a’ wave appears with the development of pulmonary hypertension and a ‘V’ wave when tricuspid incompetence occurs.

The apical impulse described as ‘tapping’ is not due to right ventricular enlargement but results from forceful closure of the mitral valve. When pulmonary vascular resistance becomes established with consequent enlargement of right ventricle, a palpable thrust in the left parasternal region become evident.

This thrust may also be the result of forward displacement of right ventricle by the enlarged left atrium. A diastolic thrill may be palpable over the apex. Pulsation of the pulmonary artery may be left in the left second intercostal space when pulmonary vascular resistance is very high. The closing sound of the pulmonary valve may be felt as a shock.

Auscultation will reveal the classical signs if the patient remains in sinus rhythm. These are — (1) loud first heart sound, (2) more or less normal second sound, (3) an opening snap, and (4) Mid-diastolic and/or presystolic murmur.

In diastole, the mitral valve leaflets are held widely open and because of the pressure difference between left atrium and left ventricle valve closure is delayed. At the onset of systole the valve leaflets have to travel a relatively long distance in order to close the valve. Rapid closure with abrupt checking of the valve leaflets by the chordae produces the loud first heart sound.

The second heart sound is audible and followed by high frequency sound the “opening snap (OS)”. This is produced by abrupt opening movement of the stenosed valve as the left ventricular diastolic pressure falls below the raised left atrial pressures. The interval between the second sound and the opening snap reflects the degree of stenosis and is certainly wider than the true splitting of the second (up to 40 milliseconds).

In severe stenosis the OS comes very close to the second sound (S₂) whereas in mild stenosis S₂-OS interval increases up to 120 milliseconds. The OS is best heard in the left fourth interspace. The loud first heart sound and opening snap are not heard when fibrosis and calcification of valve occur.

The characteristic findings in a case of pure mitral stenosis are the presence of a rumbling mid-­diastolic murmur due to turbulent flow through narrow mitral orifice. Since the closure of the valve is delayed and there is some diastolic flow as the mitral valve is closing the flow across a diminishing valve orifice, produces the presystolic murmur.

Atrial contraction in the later part of the ventricular diastole perhaps also contributes to the presystolic accentuation. The length of the diastolic muripur also reflects the degree of the seventy of the stenosis. The diastolic murmur is often best heard in a localised area located near the apex of the heart.

In presence of low cardiac output and large right ventricle it may be necessary to listen lateral to the apex with the patient lying on his left side. When atrial fibrillation develops, the presystolic accentuation may disappear. With the onset of raised pulmonary vascular resistance, the physical signs tend to be different.

The patient usually has peripheral cyanosis with cool extremities and small volume pulse. Systemic venous pressure starts rising and auscultatory signs become less florid. Pulmonary incompetence secondary to pulmonary hypertension may produce an early diastolic murmur at the pulmonary area (Graham Steel murmur) with accentuated second heart sound.

With the development of tricuspid incompetence a pansystolic murmur becomes audible over the tricuspid area. This murmur usually becomes more pronounced during inspiration. A prominent systolic ‘V’ wave in the neck and enlarged pulsatile liver and common accompaniments of tricuspid incompetence.

Assessment of severity of stenosis based on auscultatory signs alone is not of sufficient accuracy; the degree of pulmonary vascular changes shown in chest X-ray and cardiac catheterisation are more reliable indices of severity of stenosis.

Complications:

Atrial fibrillation, pulmonary hypertension congestive cardiac failure systemic pulmonary embolism are recognised complications of mitral stenosis. Hoarseness of voice and dysphagia are far too rare. The rapid ventricular rate at the onset of atrial fibrillation (AF) is a serious implication of mitral stenosis, because the time available for diastolic filling of the left ventricle is drastically reduced, pulmonary venous pressure raises sharply and pulmonary oedema may be precipitated AF also contributes to the development of left atrial thrombus and systemic embolism.

Pulmonary hypertension develops gradually over the years. About 20 per cent patients show reactive pulmonary hypertension with diffuse pulmonary arteriolar narrowing, thus exchanging pulmonary congestion for right heart failure.

Electrocardiogram:

In presence of sinus rhythm the ECG shows presence of left atrial enlargement. The ‘P’ wave is bifid in lead II and has a wide late negative component in V₁. Evidence of right ventricular enlargement, i.e. a tall R wave in lead V₁ and tall peaked P wave in leads II, HI and avF will suggest pulmonary hypertension. Atrial fibrillation is quite common.

X-Ray Examination:

The chest X-ray provides useful information about cardiac silhouette and the lung fields in mitral stenosis.

Cardiac Silhouette:

The heart is usually not enlarged.

Left atrial enlargement gives rise to:

(1) Double contour of the right border of the heart.

(2) Elevation of the left main bronchus with splaying of the carinal angle.

(3) Straightening of the left border of the heart (mitralisation) by the enlarged left atrial appendage may also produce a localised bulge immediately below the pulmonary artery.

(4) Posterior displacement of the barium filled oesophagus in the lateral view of the chest following barium swallow.

(5) Enlargement of main pulmonary artery when pulmonary hypertension is well established.

(6) Calcification of the valve or of left atrium.

Lung Fields:

A good correlation has been observed between the left atrial pressure and changes in the lung fields. With left atrial pressures of 15 mm. Hg. there is diversion of blood to the upper lobes with dilatation of pulmonary veins. When the left atrial pressure exceeds 20 mm. Hg. oedema of inter­lobular septa are seen as Kerley ‘B’ lines, associated interstitial oedema.

Left atrial pressure above 30 mm. Hg. results in alveolar oedema and perihilar haze and collection of fluid in the pleural space. When pulmonary hypertension sets in, pulmonary venous congestion is replaced by dilatation of the proximal part of the pulmonary arteries with peripheral pruning of distal vessels. Long-standing cases may demonstrate miliary mottling resulting from pulmonary haemosiderosis.

Cardiac catheterisation and cine angiogram — are not usually necessary for diagnostic accuracy since the echocardiogram provides useful information and is an important non-invasive diagnostic tool.

Echocardiogram:

It characteristically demonstrates reduced closure rate of the anterior leaflet of the mitral valve with loss of significant reopening of the valve with the atrial systole.

Differential Diagnosis:

The two important conditions which resemble the physical findings of mitral stenosis are left atrial myxoma and cor triatrium.

Features suggestive of myxoma are:

(a) Absence of history of rheumatic fever.

(b) Short history of illness.

(c) Syncope on change of posture.

(e) Constitutional symptoms — fever, arthralgia, raised ESR and abnormal globulins.

(f) Female male ratio as high as 10: 1. On auscultation the diastolic murmur changes with change of posture.

(g) Echocardiogram is very helpful in confirming the diagnosis.

In cor triatrium, the left atrium is divided by a septum separating the pulmonary veins from the mitral valve orifice. The opening in the septum produces a pressure gradient. Cardiac catheteri­sation and angio-cardiogram are necessary for diagnosis.

Management of Mitral Stenosis:

Ideal treatment of mitral stenosis is essentially surgical. Therefore medical treatment is almost entirely symptomatic.

Mild dyspnoea generally responds to diuretics and measures to prevent recurrence of rheumatic activity is all that is necessary. Atrial fibrillation (AF) can usually be controlled by digoxin. In some cases if tachycardia cannot be controlled by digoxin alone small dose of a beta-blocker (Propranolol) may help, provided cardiac failure has been excluded.

Electrical cardioversion after preliminary anticoagulation may be considered in young patients with atrial fibrillation, but is generally unhelpful as the underlying conditions continue to remain. When AF becomes established, in absence of any definite contraindication, anticoagulants can be used.

Surgical treatment comprises of mitral valvotomy or commissurotomy. It usually gives good results if the valve is pliant but mitral incompetence may occur if the valve is less narrowed than usual and is operated too early.

Indications for Mitral Valvotomy:

(1) Presence of significant symptoms, limiting activity.

(2) If pulmonary oedema develops without precipitating cause or if it develops during pregnancy.  

(3) If atrial fibrillation is causing deterioration of the clinical condition.

(4) If an episode of embolism has occurred.

The following criteria are to be carefully considered for selecting patients for operation:

(1) Presence of significant symptoms.

(2) Valves must be pliant.

(3) Absence of mitral incompetence.

(4) Absence of calcification of the valve.

In absence of these criteria, mitral valve replacement should be considered.

A second or even a third mitral valvotomy may have to be performed when restenosis occurs or when the first operation has failed to relieve the mechanical block. Raised pulmonary vascular resistance is not a contraindication for surgery and a satisfactory reversal of pulmonary vascular disease can be achieved after operation.

Prognosis:

With the introduction of mitral valve surgery the prognosis of patients with mitral stenosis has certainly become good. Although the lesion cannot be cured and myocardial involvement cannot be reversed by surgery, relief of dyspnoea and prevention of attacks of pulmonary oedema can be assured.