Prosthesis-Patient Mismatch after Mitral Valve Replacement: Comparison of Different Methods of Effective Orifice Area Calculation

The incidence of prosthesis-patient mismatch (PPM) after mitral valve replacement (MVR) has been reported to vary. The purpose of the current study was to investigate incidence of PPM according to the different methods of calculating effective orifice area (EOA), including the continuity equation (CE), pressure half time (PHT) method and use of reference EOA, and to compare these with various echocardiographic variables. We retrospectively reviewed 166 individuals who received isolated MVR due to rheumatic mitral stenosis and had postoperative echocardiography performed between 12 and 60 months after MVR. EOA was determined by CE (EOA(CE)) and PHT using Doppler echocardiography. Reference EOA was determined from the literature or values offered by the manufacturer. Indexed EOA was used to define PPM as present if ≤1.2 cm²/m². Prevalence of PPM was different depending on the methods used to calculate EOA, ranging from 7% in PHT method to 49% in referred EOA method to 62% in CE methods. The intraclass correlation coefficient was low between the methods. PPM was associated with raised trans-prosthetic pressure, only when calculated by CE (p=0.021). Indexed EOA(CE) was the only predictor of postoperative systolic pulmonary artery (PA) pressure, even after adjusting for age, preoperative systolic PA pressure and postoperative left atrial volume index (p