(P192) LONG-TERM OUTCOMES OF ISOLATED MECHANICAL VERSUS BIOPROSTHETIC MITRAL VALVE REPLACEMENT IN PROPENSITY MATCHED PATIENTS

Background: Prosthesis choice in mitral valve replacement (MVR) is often associated with age. Because of long-term durability, young patients often receive mechanical prostheses, whereas older patients often receive bioprostheses. However, in patients aged 55-75 years, optimal valve choice has not been definitively clarified. Previous studies comparing mechanical and bioprosthetic MVR have included large proportions of combined operations, wherein risks and benefits are influenced by concomitant procedures. The aim of the present study is to compare long-term outcomes of isolated mechanical versus bioprosthetic MVR using propensity matched populations.

METHODS AND RESULTS: From January 2000 to December 2017, 1954 isolated MVR (821 mechanical, 1133 bioprosthetic) were performed in British Columbia. Propensity matching based on demographics, cardiac and non-cardiac comorbidities, illness severity, and previous cardiac intervention yielded 445 each of mechanical and bioprosthetic MVR, each with 226 patients aged < 65 years and 171 patients aged 65-75 years. Patients were followed up for a mean 12.6 years. Primary outcomes included survival and freedom from reoperation. Combining all ages, 10-year survival was similar between groups (mechanical 51% vs bioprosthetic 36%; p=0.14). However, 10-year freedom from reoperation was significantly better with mechanical MVR (49% vs 32%; p=0.005). For patients younger than 65 years, 10-year survival with mechanical MVR was significantly higher than that with bioprosthetic MVR (53% vs 38%; p=0.048), as was 10-year freedom from reoperation (51% vs 31%; p< 0.001). For patients between 65-75 years, 10-year survival (50% vs 40%; p=0.74) and 10-year freedom from reoperation (49% vs 39%; p=0.23) were similar. Rates of post-operative stroke, gastrointestinal bleeding, renal failure, and permanent pacemaker insertion were similar between groups.

Conclusion: In patients younger than 65 years, mechanical MVR confers significantly higher long-term survival and freedom from reoperation when compared to bioprosthetic MVR. Patients aged 65-75 years appeared to have similar survival and reoperation rates. Focused, large study is likely required to elucidate optimal valve choice for patients aged 65-75 years.