Mitral Regurgitation

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What are the causes of mitral regurgitation?

• a.

  (Primary) degenerative mitral regurgitation is due to an abnormality of the mitral valve annulus, leaflets, or chordae tendineae. Principal causes include:

  • Mitral valve prolapse

  • Valvular degeneration

  • Annular calcification

  • Rheumatic fever

  • Endocarditis

  • Ruptured chordae tendineae

  • Ruptured papillary muscle

• b.

  (Secondary) functional mitral regurgitation is due to an abnormality of the left ventricle causing valvular distraction and leak despite structurally intact valve. Principal causes include:

  • Cardiomyopathy

  • Myocardial/papillary muscle ischemia

  • Myocardial infarction

2

What is the pathophysiology of mitral regurgitation?

In a healthy heart, the mitral valve prevents retrograde flow between the left ventricle into the left atrium during systole. However, with mitral regurgitation each ventricular contraction ejects blood via two routes: (1) antegrade, through the aortic valve and (2) retrograde, through the mitral valve. The percentage of each stroke volume inappropriately ejected retrograde into the left atrium is termed the regurgitant fraction . The regurgitant fraction joins blood returning from the pulmonary veins causing increased left atrial pressures, which are transmitted back into the left ventricle during diastolic filling. In order to compensate for the regurgitant fraction and maintain cardiac output, the left ventricle must increase the total stroke volume. This produces left ventricular volume overload, dilation, dysfunction, and possibly arrhythmias.

3

What are the symptoms of mitral regurgitation?

Most people are asymptomatic until there is severe regurgitation. When this occurs, people exhibit symptoms of heart failure, including dyspnea on exertion, loss of exercise tolerance, fatigue, and eventually increased peripheral edema.

4

What murmur is associated with mitral regurgitation?

A holosystolic murmur, which is best heard at the precordium with radiation to the left axilla.

5

What determines left atrial pressure in mitral regurgitation?

The compliance of the left atrium.

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