Incidence of prosthesis-patient mismatch in patients receiving mitral Biocor® porcine prosthetic valves

Background: The aim was to assess the incidence of prosthesis-patient mismatch (PPM) after mitral valve replacement (MVR) in patients receiving Biocor (R) porcine or mechanical valves, and to evaluate the effect of PPM on long-term survival. Methods: All patients undergoing MVR between 2009 and 2013 received either mechanical or bioprosthetic valves (Biocor (R) porcine). PPM was defined as severe when the indexed effective orifice area was <0.9 cm(2)/m(2), moderate between 0.9 cm(2)/m(2) and 1.2 cm(2)/m(2) or absent > 1.2 cm(2)/m(2). The primary endpoint was all-cause long-term mortality. Results: Among a total of 136 MVR, PPM was severe in 27%, moderate in 44% and absent in 29% of patients. Implanted valves were 57% mechanical and 43% bioprosthetic. Only 3% of patients with mechanical valves had severe PPM vs. 59% with bioprostheses (p < 0.0001). Sixty-month survival with severe mismatch was 0.559 (SE 0.149) and with no mismatch 0.895 (SE 0.058) (p = 0.043). Survival of patients suffering from severe mismatch, or moderate mismatch with pulmonary hypertension (PH) was 0.749 (SE 0.101); while for patients with no mismatch or with moderate mismatch without PH, survival was 0.951 (SE 0.028) (p = 0.016). Conclusions: About one-fourth of patients had severe PPM and almost all of them had received a bioprosthesis. Sixty-month survival was significantly lower in patients with severe mismatch, or moderate mismatch with PH. Specifically, when a bioprothesis is chosen and while further evidence on the impact of PPM on clinical outcomes appears, surgeons are recommended to follow a preoperative strategy to implant a mitral prosthesis of adequate size in order to prevent PPM.