What type of murmur is commonly associated with left ventricular (LV) systolic dysfunction?

Functional Mitral Regurgitation with Holosystolic or Midsystolic Murmur

Left ventricular systolic dysfunction most commonly produces functional mitral regurgitation, which presents as either a holosystolic (pansystolic) murmur when chronic and established, or a midsystolic murmur in less severe cases. 1, 2

Primary Murmur Characteristics

The holosystolic murmur is the classic finding in chronic functional mitral regurgitation with LV systolic dysfunction:

• Begins with S1 and continues through systole until S2, representing continuous regurgitant flow throughout ventricular contraction 1
• Best heard at the cardiac apex (left ventricular apex) 3
• Radiates to the axilla, which is pathognomonic for mitral regurgitation 2
• Indicates an established pressure gradient between the left ventricle and left atrium 1

Midsystolic murmurs can also occur with functional mitral regurgitation:

• The American Heart Association guidelines specifically distinguish functional mitral regurgitation as producing a midsystolic murmur rather than pansystolic in some cases 2
• Requires echocardiography to distinguish from benign flow murmurs or aortic stenosis 1

Clinical Context and Prevalence

Functional mitral regurgitation is extremely common in LV systolic dysfunction:

• Occurs in 56% of patients with LV ejection fraction <40% and symptomatic heart failure 4
• Results from LV remodeling causing geometric distortion of the subvalvular apparatus, global LV dilatation, and mitral annular dilatation—not from structural valve disease 5, 6
• The severity of mitral regurgitation is unrelated to the degree of LV dysfunction (ejection fraction) 6

Bedside Diagnostic Maneuvers

Use dynamic auscultation to confirm the diagnosis:

• Isometric handgrip exercise increases mitral regurgitation murmur intensity 1
• Left-sided murmurs (including mitral regurgitation) are louder during expiration 1, 3
• Standing diminishes the murmur, unlike hypertrophic cardiomyopathy or mitral valve prolapse which intensify 1, 3

Critical Pitfall to Avoid

Do not confuse functional mitral regurgitation with acute mitral regurgitation:

• Acute mitral regurgitation (from papillary muscle rupture or acute chordal rupture) produces an early systolic murmur that begins with S1 but ends in midsystole 1, 3
• This is a surgical emergency and presents with acute heart failure, requiring urgent echocardiography 1

Prognostic Significance

The presence of functional mitral regurgitation independently predicts mortality:

• Moderate to severe mitral regurgitation significantly worsens survival at 1,3, and 5 years compared to mild or no mitral regurgitation 4
• Mitral regurgitation is an independent predictor of mortality (hazard ratio 1.23) after adjusting for other clinical variables 4

Mandatory Next Step

Echocardiography is required in all cases:

• Confirms the diagnosis and quantifies severity 2, 7
• Physical examination alone has limited accuracy for determining the exact cause of systolic murmurs, especially when multiple lesions are present 7
• Urgent echocardiography is mandatory for new systolic murmur with acute heart failure, hypotension, or shock 1