Comparison of porcine bioprostheses and mechanical prostheses in multiple valve replacemente operations. Discussion

The performance of porcine bioprostheses and mechanical prostheses in multiple valve replacement operations was evaluated in 494 patients with 553 operations between 1975 and 1992. Porcine bioprostheses were implanted in 351 multiple replacement operations and 202 operations were performed with mechanical prostheses. The mean age of the bioprosthesis group was 59.1 ± 14.4 years and of the mechanical prostheses group, 55.9 ± 13.3 years. Concomitant procedures, primarily coronary artery bypass grafting, were performed in 27.4% (96 patients) of the bioprosthesis group and 20.8% (42 patients) of the mechanical prosthesis group (p = not significant [NS]). The early mortality for the bioprosthesis group (BP) was 12.0% (42 patients), whereas for the mechanical prosthesis (MP) group it was 10.9% (22 patients) with no difference (p = NS) for the performance with or without concomitant procedures, primarily coronary artery bypass grafting. The total cumulative follow-up was 1,914 years for BP and 458 years for MP group. The late mortality was different between the groups (p < 0.05), 6.1%/patient-year for BP and 3.7%/patient-year for MP. The difference in late mortality was not different (p = NS) for performance of concomitant procedures and not different (p = NS) for the absence of concomitant procedures, 5.6%/patient-year for BP and 2.2%/patient-year for MP. The freedom from thromboembolism- and antithromboembolic-related hemorrhage favored the biological population (p < 0.05) at 10 years with 79.7% ± 3.4% for BP and 75.4% ± 5.0% for MP. The freedom from structural valve deterioration was 100% for MP, whereas for the BP group, 94.7% ± 1.6% at 5 years and 65.9% ± 4.3% at 10 years. The freedom from valve-related mortality was not different (p = NS), at 10 years, 83.9% ± 3.3% for bioprostheses and 96.8% ± 1.4% for mechanical prostheses. The freedom from residual morbidity (permanent impairment) was different (p < 0.05), 93.6% ± 2.2% for bioprostheses and 91.7% ± 3.1% for mechanical prostheses. The freedom from valve-related reoperation did not differentiate the groups (p = NS) for BP, 94.5% ± 1.5% at 5 years and 60.4% ± 4.4% at 10 years and for MP, 95.5% ± 2.5% at 5 years and 86.8% ± 8.5% at 10 years. The freedom from fatal reoperation was 93.5% ± 2.5% for BP and 98.8% ± 0.8% for MP at 10 years (p = NS). The overall complications favored the biological group (p < 0.05) with freedom at 5 years of 80.9% ± 2.5% for BP and 71.6% ± 5.0% for MP, but by 10 years it was 41.7% ± 4.1% for BP and 71.6% ± 5.0% for MP. The early mortality for reoperation in these multiple valve replacement groups was 16.3% overall, 15.3% for the bioprostheses group (13 of 85 patients) and 28.6% for the mechanical group (2 of 7 patients) (p = NS). Twenty-four patients had incidental replacement of an additional bioprosthesis at reoperation without a fatality. Bioprostheses in multiple valve replacement operations provided less valve-related morbidity and equivalent freedom from reoperative mortality when clinical performance of these bioprostheses and mechanical prostheses was evaluated.