Reoperation in biological and mechanical valve populations : fate of the reoperative patient. Discussion

From 1975 through 1992 inclusive, reoperative valve replacement (REOP) was required by 12.9% of patients (708/5,499). Of 1,355 patients with mechanical prostheses (MP), 46 (3.4%) came to REOP versus 662 of 4,144 patients (16%) with biological prostheses (BP). Early REOP mortality rate was 17.4% (8/46) for MP and 10.6% (70/662) for BP (p = not significant). It was higher with age greater than 75 years (p < 0.05) and trended higher with concomitant procedures and with increasing number of REOPs (p = not significant). The percentage freedom from REOP at 5 and 10 years for all BP was 96.0% ± 0.4% and 74.9% ± 1.1% compared with 93.6% ± 1.2% and 87.9% ± 2.5% for MP. The most common cause of REOP in the BP patients was structural valve deterioration, which was uncommon in patients with MP (72% versus 2% of REOP but only 15% versus 0.1% of initial implants). Nonstructural dysfunction was the leading cause of REOP in the MP group (65% versus 11%). Prosthetic valve endocarditis (18% versus 10%) and thromboembolic complications (10% versus 1%) were also more frequent causes of REOP in MP patients. However, the increased relative role of these factors with MP is due to the minimal incidence of structural valve deterioration. When related to the original choice of MP versus BP, only thromboembolic complication (3.8 times) was more prevalent as a cause of REOP in patients receiving MP at their previous procedure (p = not significant). For patients who previously received BP, structural valve deterioration (69 times) was more likely to lead to REOP than with MP (p < 0.01). At REOP a patient with MP is much more likely to get a second MP (85%) than a BP patient to get a second BP (58%). This study demonstrates a 1.9 times increase in REOP procedural risk with MP versus BP, but when related to initial/previous prosthesis selection, only 0.24%/pt-y (8/1,309) and 0.28%/pt-y (70/3,482) patients died at REOP, no difference in risk if a BP had been selected initially. The probability of REOP death was low regardless of the type of prosthesis first implanted, and long-term results after REOP were generally excellent except in the previous MP to BP replacement group. Selective prescription of MP versus BP based on age, risk of systemic anticoagulation, lifestyle, and other individual features remains appropriate.