CHOICE OF MITRAL PROSTHESIS IN THE ELDERLY - AN ANALYSIS OF ACTUAL OUTCOME

Background-In younger patients requiring mitral valve replacement (MVR ), mechanical prostheses (MPs) have been reported to give better freed om from all valve-related complications (VRCs) because of the high inc idence of late valve degeneration (VD) associated with bioprostheses ( BPs). In older patients, however, the risk of VD may be reduced becaus e of the large competing risk of noncardiac death (NCD). Previous stud ies on VD in the elderly have used actuarial analysis, which overestim ates the risk of VD in this population because it assumes that dead pa tients are still at risk. In contrast, cumulative incidence tactual) a nalysis acknowledges that patients who die have no risk of VD. This st udy compares the results of both ''actual'' and ''actuarial'' analyses of the freedom from VD in elderly patients undergoing MVR. Methods an d Results-From June 1976 through January 1996, 504 patients 970 years of age underwent MVR at our institution. Isolated mitral operations we re performed in 159 patients, and 169 had concomitant CABG. Hospital m ortality was 59 of 374 (15.9%) for tissue prosthesis versus 24 of 130 (18.5%) for mechanical prosthesis (P=NS). For tissue versus mechanical prosthesis, 10-year freedom from noncardiac death was 75.0% versus 67 .6% (P=NS); 10-year actuarial freedom from valve degeneration was 79.8 % versus 93.4% (P=NS); 10-year actual freedom from valve degeneration was 92.6% versus 95.4% (P=NS); and 10-year actual freedom from all VRC s was 84.4% versus 92.3% (P=NS). Conclusions-in elderly patients under going MVR, actuarial analysis overestimates the 10-year risk of VD com pared with actual analysis (20.2% versus 7.4% for BP, 6.6% versus 4.6% for MP). In these patients, the actual freedoms from VD and all VRCs do not differ significantly between BP and MP. Thus, in this age group , the necessity for anticoagulation or its avoidance may be the predom inant factor in choosing a replacement mitral valve.