Determinants of depressed left ventricular ejection fraction in pure mitral stenosis with preserved sinus rhythm

Although depressed left ventricular ejection fraction is present in a considerable proportion of subjects with pure mitral stenosis (MS), its mechanisms are not clearly identified. The purpose of this study was to identify determinants of depressed ejection fraction in young patients with isolated mitral stenosis in sinus rhythm.

We retrospectively analyzed 320 records of patients with MS (mitral valve area < or = 2.0 cm2) who underwent invasive diagnostic procedure in our center. Of these 39 subjects aged 20-40 years with isolated MS in sinus rhythm were selected for the final analysis.

An ejection fraction not exceeding 50% was found in 12 patients (group A). When comparing group A to the remainder (group B), group A patients had lower left ventricular end-diastolic volume indices (60.5 +/- 21.6 ml/m2 vs. 76.1 +/- 16.1 ml/m2, p = 0.02) and stroke volume indices (28.0 +/- 10.4 vs. 47.9 +/- 12.0, p < 0.001). No significant differences between the groups in patients' age, end-systolic volume index, mitral valve area, mean transmitral gradient, left-sided cardiac pressures, pulmonary wedge pressure, systemic vascular resistance, and cardiac output were found. Indices of left ventricular isovolumic contraction and relaxation as well as end-systolic indices of left ventricular function were also comparable. Group A had significantly higher pulmonary vascular resistance, pulmonary artery pressures, and higher heart rate. An approximate index of left ventricular compliance was significantly lower in group A with similar left ventricular minimal and end-diastolic pressures.

Depressed ejection fraction in pure mitral stenosis with preserved sinus rhythm seems attributable to left ventricular underfilling that appears to be precipitated by other factors in addition to a narrowed mitral orifice, e.g. decreased passive left ventricular compliance and/or altered interventricular interactions.