Systolic Murmurs - Mitral Regurgitation

     You are listening to a typical example of a murmur caused by mitral valve regurgitation. Mitral valve regurgitation is usually either a congenital condition or a consequence of rheumatic heart disease, marked left ventricular dilatation, acute infective endocarditis, or papillary muscle dysfunction secondary to acute or prior myocardial infarction.

     This murmur is usually best heard at the apex, with radiation into the axilla. Because the mitral valve is unable to contain the blood within the ventricle for the entire systolic period, it is a holosystolic murmur. The quality of the murmur is usually described as blowing, and, as subtly demonstrated in the sample you are hearing, it is often associated with an S3 because of the left atrial volume overload. Although S1 is due to a combination of mitral and tricuspid valve closure, the mitral valve is the louder aspect. Because the valve closure in mitral regurgitation is incomplete, S1 may be noticeably quieter. Finally, in severe regurgitation, the pressure in the left ventricle quickly equalizes with venous pressure in the left atrium during the start of diastole. The result is that the aortic valve may close prematurely and may, although not present in this sample, occasionally result in a widely split S2.

     A maneuver which may increase the intensity of mitral regurgitation is transient arterial occlusion. When blood pressure cuffs are used to completely occlude the brachial artery for a short period, the resultant increase in arterial resistance causes the left ventricle to increasingly favor the regurgitant mitral valve as an outlet for flow. This flow increase will enhance the intensity of the murmur.