Location and Characteristics of Functional Mitral Regurgitation Murmur in Dilated Cardiomyopathy
In a patient with severe dilated cardiomyopathy and functional mitral regurgitation, the murmur is best heard at the cardiac apex with the patient in the left lateral decubitus position, and it typically presents as a softer, less impressive systolic murmur that may be non-holosystolic or even biphasic—distinctly different from the loud holosystolic murmur of primary mitral regurgitation. 1
Auscultation Location
The murmur is loudest at the apex (left ventricular apex, typically the 5th intercostal space at the midclavicular line). 1
Optimal positioning is the left lateral decubitus position, which brings the apex closer to the chest wall and enhances detection of the murmur. 1
The murmur may radiate to the axilla, though this is less consistent in functional MR compared to primary MR. 1
Sound Characteristics: Key Differences from Primary MR
Timing and Quality
Functional MR often produces a softer, less impressive systolic murmur that does not match the hemodynamic severity of the regurgitation—a critical pitfall that can lead to underestimation of disease severity. 1
The murmur may be non-holosystolic or biphasic rather than the classic holosystolic pattern seen in primary MR. 2, 1
In functional MR with dilated cardiomyopathy, a biphasic pattern with prominent early systolic flow is common, where the jet is largest in very early systole and then diminishes in mid- and late systole. 2
Midsystolic murmurs can occur in functional MR, which differs from the typical holosystolic pattern and may be mistaken for a flow murmur or aortic stenosis. 2
Intensity Considerations
Murmur intensity does not reliably reflect severity in functional MR—even hemodynamically significant regurgitation may produce only a soft murmur. 1
The murmur is typically medium-to-high-pitched but softer than expected for the degree of regurgitation. 1
Associated Physical Examination Findings
An S3 gallop is an objective sign of significant volume overload and indicates at least moderate-to-severe regurgitation, providing more reliable severity assessment than murmur intensity alone. 1
In acute severe MR (such as from papillary muscle rupture), expect a loud holosystolic murmur at the apex plus an early diastolic filling sound (S3), indicating rapid volume overload. 1
Normal left-ventricular and left-atrial examination (no dilation, normal impulse) makes severe chronic mitral regurgitation unlikely, even if echocardiography suggests otherwise. 1
Dynamic Auscultation in This Context
Left-sided murmurs are usually louder during expiration as increased venous return augments left heart filling. 2
Handgrip exercise increases afterload and typically augments the intensity of MR murmurs by increasing the regurgitant volume. 2
In functional MR, severity varies with loading conditions, blood pressure, and heart rate, so findings may change between examinations. 1
Critical Pitfalls in Functional MR
Eccentric jets may produce deceptively soft murmurs, leading clinicians to underestimate severity when relying on murmur intensity alone—this is particularly problematic in functional MR where jets are often directed posteriorly. 1
Anterior leaflet "override" in dilated cardiomyopathy is not true prolapse; the leaflet never moves superior to the annular plane into the left atrium, despite appearing to override the posterior leaflet on imaging. 2
When physical examination suggests severe MR (loud murmur, S3, volume-overload signs) but echocardiography reports only mild regurgitation, the imaging likely underestimates severity because of an eccentric jet or technical limitations. 1
Conversely, when echocardiography reports severe MR but examination reveals only a very late, soft murmur with normal chamber sizes, the imaging may have overestimated severity by not accounting for late-systolic-only regurgitation. 1
Mechanism-Specific Considerations in Dilated Cardiomyopathy
Functional MR in dilated cardiomyopathy results from leaflet tethering and annular dilatation rather than primary leaflet pathology, which explains the different acoustic characteristics. 2, 3, 4
The severity depends on mitral valve tenting, papillary muscle displacement, and left ventricular sphericity—all geometric deformations that affect coaptation without creating the high-velocity jets typical of primary MR. 3, 4, 5, 6
Coaptation height is the strongest independent determinant of effective regurgitant orifice area in both ischemic and non-ischemic dilated cardiomyopathy. 4