Rheumatic mitral regurgitation

Rheumatic mitral regurgitation

Mitral valve is the commonest valve involved in rheumatic heart disease. Mitral regurgitation occurs in the early phase of acute rheumatic fever itself. In fact it is almost an invariable association of rheumatic carditis. In very early stages of rheumatic carditis, the mitral regurgitation can be clinically silent, but demonstrable by Doppler echocardiography. Some studies have shown that Doppler echocardiographic detection of mitral regurgitation in the acute phase of rheumatic carditis predates clinical detection by up to two weeks. Many of the cases of mitral regurgitation due to rheumatic carditis resolve later on or decrease in severity on follow up. Even though the carditis in rheumatic fever is a pancarditis, the predominant involvement is that of the endocardium in the form of valvular involvement. Hence the mechanism of mitral regurgitation in the acute phase is mainly valvular and seldom due to left ventricular dilatation due to myocarditis and left ventricular failure. But significant mitral regurgitation itself can set up a vicious cycle because left ventricular dilatation caused by mitral regurgitation can further increase the mitral regurgitation by the dilatation of the mitral annulus which decreases the coaptation of the mitral leaflets in systole.

Clinically chronic rheumatic mitral regurgitation is associated with a left ventricular forceful apical impulse, cardiomegaly, soft first heart sound, left ventricular third heart sound and an apical pansystolic murmur which is conducted to the axilla. The conduction to axilla differentiates the murmur from the murmur of papillary muscle dysfunction and mitral regurgitation, which is usually conducted to the base of the heart. Sometimes late systolic pulsation of the left parasternal region due to the expansion of the left atrium may also be felt.

The electrocardiogram may show PR interval prolongation in the acute phase of rheumatic mitral regurgitation with carditis. In chronic rheumatic mitral regurgitation of significant severity, ECG shows left atrial and left ventricular enlargement.

The chest x-ray shows cardiomegaly and left atrial enlargement in severe rheumatic mitral regurgitation. Pulmonary congestion and features pulmonary hypertension may occur in late stages. Pulmonary congestion and cardiac failure can also occur in the acute phase if the rheumatic carditis is fulminant.

Echocardiography shows thickening of the mitral leaflets with tethering of the posterior mitral leaflet with restriction of movement. But frank reversal of movement (paradoxical anterior movement of posterior leaflet in diastole) as in mitral stenosis does not occur in isolated rheumatic mitral regurgitation. Immobility of the posterior leaflet is the hallmark of rheumatic mitral regurgitation which differentiates it from nonrheumatic mitral regurgitation on echocardiography. Systolic separation of the mitral leaflets can be seen sometimes. Dilated left atrium and left ventricle gives a suggestion that the mitral regurgitation is significant. Doppler echocardiography is needed to confirm mitral regurgitation and quantify it. The intensity of the spectral tracing and depth to which the jet is located by pulsed Doppler is an indication of severity of mitral regurgitation. By color Doppler, the area of the jet in relation to the left atrium determines the severity. The depth to which the jet reaches in the left atrium is also an important determinant of severity.

According to the World Heart Federation criteria [1] morphological features of rheumatic mitral valve involvement on echocardiography are:

1. Anterior mitral valve thickening of 3 mm or more
2. Chordal thickening
3. Restricted leaflet motion
4. Excessive leaflet tip motion during systole

Unlike the mitral valve in non-rheumatic mitral regurgitation, the heavily scarred mitral valve in rheumatic mitral regurgitation may not be always suitable for a conservative mitral valve repair procedure. Very often they end up in mitral valve replacement if severe enough to produce symptoms or impairment of left ventricular function.

Reference

1. Reményi B, Wilson N, Steer A, Ferreira B, Kado J, Kumar K, Lawrenson J, Maguire G, Marijon E, Mirabel M, Mocumbi AO, Mota C, Paar J, Saxena A, Scheel J, Stirling J, Viali S, Balekundri VI, Wheaton G, Zühlke L, Carapetis J. World Heart Federation criteria for echocardiographic diagnosis of rheumatic heart disease–an evidence-based guideline. Nat Rev Cardiol. 2012 Feb 28;9(5):297-309.