Systolic regurgitant murmur in dilated cardiomyopathy
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dilated cardiomyopathy systolic regurgitant murmur functional mitral regurgitation authoritative
In dilated cardiomyopathy, a systolic regurgitant murmur is most commonly due to functional (secondary) mitral regurgitation.
- Mechanism: Left-ventricular dilation stretches the mitral annulus and displaces the papillary muscles. The mitral leaflets cannot coapt fully despite being structurally normal, so blood regurgitates from the LV to the left atrium during systole.
- Murmur: Typically high-pitched, blowing, holosystolic (pansystolic), best heard at the apex, often radiating to the left axilla.
- Other associated signs: S3 gallop, displaced diffuse apical impulse, pulmonary crackles, and signs of heart failure.
- Also consider: Functional tricuspid regurgitation can occur if pulmonary hypertension causes right-ventricular/annular dilation. Its pansystolic murmur is best at the left lower sternal border and increases with inspiration.
Echocardiography confirms the dilated, poorly contractile ventricle and quantifies secondary MR. Textbook sources describe secondary MR as a consequence of LV dysfunction, commonly from dilated cardiomyopathy, and attribute it to annular dilation and papillary-muscle dysfunction/malalignment (Goldman-Cecil Medicine, section “Secondary (Functional) Mitral Regurgitation”; Textbook of Clinical Echocardiography). The MSD overview also lists functional atrioventricular-valve regurgitation as a typical feature of dilated cardiomyopathy.
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