What mechanism by which mitral valve disease can cause heart failure is most accurately described as prolapse of the mitral valve putting increased strain on the left atrium, particularly if it results in significant mitral regurgitation?

Mitral Valve Prolapse and Heart Failure Mechanism

Prolapse of the mitral valve puts increased strain on the left atrium, particularly when it results in significant mitral regurgitation, making this the most accurate statement among the options provided.

Pathophysiologic Mechanism of Heart Failure in Mitral Valve Prolapse

The primary mechanism by which mitral valve prolapse (MVP) leads to heart failure involves retrograde blood flow from the left ventricle into the left atrium during systole, creating volume overload and progressive chamber remodeling. 1

Direct Left Atrial Effects

• Mitral regurgitation from prolapse causes blood to flow backward into the left atrium during systole, directly increasing left atrial pressure and volume. 2
• The left atrium experiences chronic volume overload as it receives both normal pulmonary venous return and the regurgitant volume from the left ventricle. 1
• Progressive left atrial enlargement occurs as a compensatory response to chronic volume overload, with the left atrium dilating to accommodate the increased blood volume. 1
• This left atrial strain and enlargement can occur even with mild-to-moderate mitral regurgitation in some patients with MVP due to the underlying connective tissue abnormality. 3

Hemodynamic Cascade Leading to Heart Failure

• During left ventricular systole, there are two pathways for blood ejection: a low-impedance path through the incompetent mitral valve into the left atrium and a higher-impedance path through the aortic valve. 1
• The total left ventricular stroke volume divides between regurgitant volume (into the atrium) and forward stroke volume (through the aorta). 1
• In chronic severe mitral regurgitation from prolapse, left ventricular dilation continues with progressive left atrial enlargement and increased pulmonary venous pressures, ultimately causing signs and symptoms of heart failure. 1
• Elevated left atrial and pulmonary venous pressures lead to pulmonary congestion and shortness of breath. 2

Progression to Ventricular Dysfunction

• If the disease progresses without correction, left ventricular myocardial contractile dysfunction occurs with rapid decline in hemodynamic status and heart failure. 1
• The severity of mitral regurgitation, quantified by regurgitant fraction, serves as an index for the likelihood of progressive left ventricular myocardial remodeling, dysfunction, and eventual heart failure. 1
• Chronic volume overload from progressive mitral regurgitation induces unfavorable neurohormonal and structural changes that worsen heart failure symptoms. 1

Why the Other Statements Are Incorrect

Mitral Stenosis and Systemic Hypertension

• Mitral stenosis does not worsen systemic hypertension; rather, it causes left atrial pressure elevation and pulmonary hypertension, not systemic arterial hypertension. 1

Direct Right Atrial Stress

• Mitral regurgitation does not directly increase stress in the right atrium. The regurgitant flow goes from the left ventricle to the left atrium, not to the right atrium. 1, 2
• Right-sided effects occur secondarily through elevated pulmonary pressures affecting right ventricular function and tricuspid regurgitation. 1

Septic Disease Risk

• While endocarditis can occur in mitral valve prolapse, this is not the primary mechanism by which MVP causes heart failure. 1
• The question asks about mechanisms causing heart failure, not infectious complications. 1

Clinical Implications

The recognition that mitral valve prolapse with regurgitation causes left atrial strain and progressive chamber remodeling is critical for timing interventions before irreversible ventricular dysfunction develops. 1