Effect of abrupt mitral regurgitation after balloon valvuloplasty on myocardial load and performance

AbstractThe concept that mitral regurgitation masks myocardial dysfunction by reducing afterload and augmenting ejection performance has not been well established in humans. The effect of abruptly produced mitral regurgitation on left ventricular loading and performance was therefore evaluated in five patients who developed this complication after an otherwise successful percutaneous balloon mitral valvuloplasty. Mitral valve area by Gorlin formula calculated with forward flow increased from 0.92 ± 0.14 to 2.75 ± 0.82 cm2. Mean left atrial pressure did not decrease (19 ± 4 to 19 ± 6 mm Hg). The size of the left atrial Vwave relative to mean left atrial pressure (peak V— mean left atrial pressure) increased from 7 ± 4 to 19 ± 6 mm Hg. Angiographic mitral regurgitation increased from 0+ or 1 + to >3+ in each patient and regurgitant fraction increased from 0.23 ± 0.11 to 0.55 ± 0.99 (p < 0.01).End-diastolic volume increased modestly from 148 ± 15 to 159 ± 15 ml (p = NS). Heart rate increased from 54 ± 5 to 71 ± 8 heats/min (p < 0.05), which may have prevented further increases in preload by shortening the filling period. End-systolic stress decreased by 32% from 277 ± 34 to 188 ± 52 kdyn/cm2(p < 0.01) as a result of a 25% decrease in end-systolic pressure from 121 ± 8 to 91 ± 7 mm Hg and a 16% decrease in end-systolic volume from 67 ± 13 to 56 ± 8 ml (p = NS). Contractility estimated from the preload-corrected ejection fraction-afterload relation decreased in one of the five patients and did not increase in the others despite an increase in heart rate, possibly as a result of myocardial depression from the balloon procedure itself. Nevertheless, the decrease in end-systolic volume could not be attributed to a net increase in contractility. The result of the changes in loading was an increase in ejection fraction from 0.55 ± 0.05 to 0.65 ± 0.04 (p < 0.05).Thus, abruptly produced mitral regurgitation increases ejection performance by reducing afterload without increasing contractility. This should be taken into consideration when anticipating the results of valve replacement for acute or subacute mitral regurgitation