Mitral Valve Dysfunction Affects Both Systolic and Diastolic Function
Yes, mitral valve dysfunction significantly impacts both systolic and diastolic cardiac function through distinct but interconnected pathophysiologic mechanisms. 1
Impact on Systolic Function
Primary mitral regurgitation creates a low-impedance pathway during systole that fundamentally alters left ventricular performance:
During left ventricular systole, blood ejects through two pathways: a low-impedance path backward through the incompetent mitral valve into the left atrium (10-20 mmHg pressure gradient) and a higher-impedance path forward through the aortic valve 1
The total left ventricular stroke volume divides between regurgitant volume (30-50% in severe disease) and forward stroke volume, with the regurgitant fraction serving as an index for progressive left ventricular myocardial remodeling and dysfunction 1
This reduced afterload paradoxically maintains or even increases ejection fraction early in the disease course (often >50%), masking underlying contractile dysfunction until irreversible myocardial damage occurs 2, 3
Chronic volume overload leads to eccentric left ventricular hypertrophy with increased compliance, and the mass-to-volume ratio remains normal initially 2
Progressive left ventricular dilation continues with worsening mitral regurgitation, ultimately causing left ventricular myocardial contractile dysfunction with rapid hemodynamic decline 1, 4
Impact on Diastolic Function
Mitral valve disease profoundly affects diastolic function through multiple mechanisms:
Mitral regurgitation causes blood to flow backward into the left atrium during systole, directly increasing left atrial pressure and volume, with 70-80% of MVP patients experiencing chronic left atrial volume overload 1
Progressive left atrial enlargement occurs as a compensatory response, with the left atrium dilating to accommodate both normal pulmonary venous return and the regurgitant volume from the left ventricle 1
Increased pulmonary venous pressures develop as left atrial strain progresses, ultimately manifesting as dyspnea and signs of heart failure 1, 3
In mitral stenosis, assessment of left ventricular diastolic function becomes more challenging, though IVRT, tissue Doppler velocities, and mitral inflow patterns remain valuable for predicting mean left atrial pressure 5
For mitral regurgitation with normal left ventricular ejection fraction, the time interval Ar-A and IVRT/TE2e′ ratio predict left ventricular filling pressures, whereas E/e′ ratio is only reliable when ejection fraction is depressed 5
Clinical Implications and Timing
The recognition that mitral valve dysfunction causes both systolic unloading and diastolic left atrial strain is critical for timing interventions:
In chronic severe mitral regurgitation, if the left atrium is distensible enough to buffer backward pressure transmission, patients may have only mild symptoms despite severe regurgitation and substantially reduced contractility 2
Surgery is indicated in symptomatic patients with severe valve disease and in asymptomatic patients before irreversible ventricular damage occurs 6
The strongest predictor of postoperative ejection fraction is preoperative ejection fraction, and mortality is significantly higher when postoperative ejection fraction remains ≤0.50 4
Chronic volume overload induces unfavorable neurohormonal and structural changes (20-50% increase in B-type natriuretic peptide) that worsen heart failure symptoms 1
Common Pitfalls
Relying solely on ejection fraction to assess systolic function in mitral regurgitation is misleading, as the reduced afterload maintains normal or elevated ejection fraction until severe irreversible myocardial dysfunction develops 2, 3
Failing to recognize that normal left ventricular and left atrial dimensions on examination make severe chronic mitral regurgitation unlikely, even if echocardiography suggests otherwise 5, 7
In secondary mitral regurgitation from left ventricular dysfunction, E/e′ ratio correlates with left atrial pressure and predicts hospitalizations and mortality, but this relationship does not hold for primary mitral regurgitation with normal ejection fraction 5