Background: Surgeons traditionally avoid the use of "small" aortic prostheses because of the potential for residual left ventricular outflow tract obstruction and persistent transvalvular gradients. This study examines the ratio between prosthetic valve size and the body surface area (BSA) of patients undergoing aortic valve replacement (AVR). We sought to determine the effect of potential "prosthesis-patient" mismatch on long-term survival.
Methods and results: Follow-up was conducted on 2981 patients who underwent AVR with stented bioprostheses between 1976 and 1996. To account for differences between manufacturers' labeled valve sizes, we calculated the ratio between the prosthetic valve effective orifice area (EOA) and the patient's BSA (recorded for 2154 patients). The lowest decile in this cohort had a calculated EOA/BSA of <0.75 cm(2)/m(2) (Small group, n=227) compared with the control group (n=1927), in whom the EOA/BSA ratio was >0.75 cm(2)/m(2). Operative mortality was higher in the Small group (8% versus 5%, P:=0.03). Actuarial survival at 12 years was 50+/-5% in the Small group compared with 49+/-2% in the control group (P:=0.27). However, freedom from valve-related mortality was significantly lower in the Small group (75+/-5% versus 84+/-2%, P:=0.004). Cox regression analysis determined age and NYHA functional class to be the multivariate predictors of overall mortality, whereas advanced age and EOA/BSA <0.75 cm(2)/m(2) were found to be the predictors of valve-related mortality.
Conclusions: Prosthesis-patient mismatch results in significantly higher early and late mortality after bioprosthetic AVR. We recommend careful selection of stented bioprostheses to ensure an adequate ratio of EOA to BSA. An EOA/BSA ratio of >0.75 cm(2)/m(2) may avoid residual left ventricular outflow tract obstruction and persistent transvalvular gradients. Careful prosthesis-patient matching will improve both early and late survival after AVR.