Patient prosthesis mismatch is rare after aortic valve replacement: Valve size may be irrelevant - Discussion

Background. Although small valve size and patient-prosthesis mismatch are both considered to decrease long-term survival, little direct evidence exists to support this hypothesis. Methods. To assess the prevalence of patient-prosthesis mismatch and the influence of small valve size on survival, we prospectively studied 1,129 consecutive patients undergoing aortic valve replacement between 1990 and 2000. Mean and peak gradients and indexed effective orifice area were measured by transthoracic echocardiography postoperatively (3 months to 10 years). Abnormal postoperative gradients were defined as those patients with mean or peak gradient above the 90th percentile (mean gradient ≥ 21 or peak gradient ≥ 38 mm Hg). Patient-prosthesis mismatch was defined as those patients with indexed effective orifice area below the 10th percentile (< 0.60 cm2/m2). Results. A multivariable analysis identified internal diameter of the implanted valve as the only independent predictor of abnormal gradients postoperatively. However, there was no significant difference in actuarial survival between normal and abnormal gradient groups (7 years: 91.2% ± 1.5% versus 95.0% ± 2.2%; p = 0.48). Freedom from New York Heart Association class III or IV (7 years: 74.5% ± 3.1% versus 74.6% ± 6.2%; p = 0.66) and left ventricular mass index were not different between normal and abnormal gradient groups. Patients with and without patient-prosthesis mismatch were similar with respect to postoperative left ventricular mass index, 7-year survival (95.1% ± 1.3% versus 94.7% ± 3.0%; p = 0.54), and 7-year freedom from New York Heart Association class III or IV (79.3% ± 6.6% versus 74.5% ± 2.5%; p = 0.40). In patients with patient-prosthesis mismatch and abnormal gradients, the majority had prosthesis dysfunction owing to degeneration. Conclusions. Severe patient-prosthesis mismatch is rare after aortic valve replacement. Patient-prosthesis mismatch, abnormal gradient, and the size of valve implanted do not influence left ventricular mass index or intermediate-term survival. © 2002 by The Society of Thoracic Surgeons.