THE EFFECTS OF COMPLETE VERSUS INCOMPLETE MITRAL-VALVE REPAIR IN EXPERIMENTAL MITRAL REGURGITATION

Severe mitral regurgitation (regurgitant fraction 0.75 +/- 0.02) was c reated in eight dogs by our closed-chest chordal rupture technique. Af ter 3 months of chronic mitral regurgitation all indices of contractil e function were depressed. Mitral valve repair was then attempted. Pos toperative regurgitant fraction was reduced compared with the preopera tive value in; all eight dogs. Concomitantly, forward cardiac output i ncreased in all, dogs and pulmonary capillary wedge pressure fell in a ll dogs. However, in some dogs, significant regurgitation persisted de spite repair. Postoperative regurgitant fraction ranged from 0% to 60% . Postoperative residual regurgitant fraction was related significantl y to postoperative cardiac output (r = 0.99), pulmonary capillary wedg e pressure (r = 0.77), ejection fraction (v 3;0.75), and two indices o f contractile function-the mass-corrected end-systolic stress volume r elationship (r = 0.87) and end-systolic stiffness (r = 0.93). In gener al, these parameters returned to their normal values before mitral reg urgitation when postoperative regurgitant fraction was less than 30%. Myocytes isolated from the ventricles at the end of study also demonst rated normal contractile function when regurgitant fraction was less t han 30%.