The Italian study of the Mitroflow postoperative results (ISTHMUS): a 20-year, multicenter evaluation of Mitroflow pericardial bioprosthesis

Objective: A multicentre experience with the Mitroflow pericardial bioprosthesis has been evaluated longitudinally over a 20-year period. Methods: From 1988 through 2008, 1591 patients (mean age, 75.3 ± 6.8 years, and 60.1% female) from 12 centres had a Mitroflow in the aortic position. Concomitant coronary artery bypass was performed in 41.9% (n = 666) of patients, urgency/emergency surgery in 9.5% (n = 152) and replacement of degenerated prosthesis in 2.3% (n = 36). Follow-up (7.447 patient-years) was 99.2% complete. Median follow-up was 61.9 months (interquartile range (IQR) 30.8-90.9 months). The study was carried out following American Association for Thoracic Surgery/Society for Thoracic Surgeons/European Association for Cardio-Thoracic Surgery (AATS/STS/EACTS) Guidelines for reporting valve morbidity and mortality. Results: The early (30-day) mortality was 6.5% (n = 104). Actuarial survival rates at 10, 15 and 18 years were 53%, 34% and 27%, respectively (2.2 patient/year). Re-operation was required in 96 patients (5.9%), of whom 59 patients (3.7%) for structural valve degeneration. Actuarial freedom from prosthetic valve degeneration at 18 years was 65.5% (78% in patients >70 years) with a linearised rate of 1.4 patient/year (0.8 patient/year in patients >70 years). At 18 years, freedom from embolism was 82% (0.9 patient/year), freedom from valve endocarditis was 89% (0.6 patient/year) and freedom from bleeding episodes was 95% (0.2 patient/year), respectively. Conclusions: This independent multicentre study indicates that the Mitroflow pericardial bioprosthesis provides favourable long-term postoperative results with a low rate of valve-related events and need of re-intervention, particularly in patients older than 70 years.