Patient-prosthesis mismatch after mitral valve replacement: myth or reality?

Determining the risk of patient-prosthesis mismatch after mitral valve replacement is still controversial. In this study, we aimed to clarify incidence and clinical implications of such a complication. The accuracy of preoperative prediction of patient-prosthesis mismatch using published in vitro hemodynamic parameters was also investigated.

Ninety-two patients who underwent mitral valve replacement and received Carpentier-Edwards stented bioprosthesis (Edwards Lifesciences, LLC, Irvine Calif) were enrolled. Hemodynamic performances were evaluated at discharge, and the incidence of in vivo patient-prosthesis mismatch (indexed effective orifice area < or =1.2 cm2/m2) was evaluated. Correlation between in vivo patient-prosthesis mismatch and predicted patient-prosthesis mismatch, based on previously published in vitro hemodynamic parameters, was also investigated.

Five patients died within 30 days of the operation (5.4% mortality). Mean prosthesis size was 29.8 +/- 2. Mean postoperative effective orifice area and indexed effective orifice area (2.5 +/- 0.8 cm2 and 1.5 +/- 0.4 cm2/m2, respectively) compared favorably with those predicted in vitro (2.2 +/- 0.7 cm2 and 1.3 +/- 0.5 cm2/m2, respectively). In the subgroup of patients receiving prosthesis size of 27 or smaller, the difference reached statistical significance (2.47 +/- 0.83 and 1.61 +/- 0.7 for postoperative and predicted effective orifice areas, respectively; P < .001). Postoperative patient-prosthesis mismatch was recorded in 8 patients (8.6%), comparing favorably with the predicted patient-prosthesis mismatch (39% for overall population and 80% for patients receiving prosthesis size < or = 27). No significant correlation between size of prosthesis and early hemodynamic and clinical outcomes was shown.

In our study, stented mitral bioprostheses showed satisfactory postoperative hemodynamic performance, even in smaller prosthesis sizes (< or =27 mm). Risk of in vivo postoperative patient-prosthesis mismatch seems to be less relevant than preoperative risk prediction based on in vitro data. Further studies are needed to evaluate the potential clinical impact of mitral patient-prosthesis mismatch.