Prosthesis-patient mismatch affects survival after aortic valve replacement

Area of Science:

• Cardiovascular Surgery
• Biomedical Engineering
• Clinical Outcomes Research

Background:

• Surgeons traditionally avoid small aortic prostheses due to concerns about left ventricular outflow tract obstruction and transvalvular gradients.
• Prosthesis-patient mismatch, where the prosthetic valve size is inadequate for the patient's body size, is a significant concern in aortic valve replacement (AVR).

Purpose of the Study:

• To investigate the impact of prosthesis-patient mismatch on long-term survival after AVR.
• To determine the relationship between the effective orifice area to body surface area (EOA/BSA) ratio and patient outcomes.

Main Methods:

• Retrospective analysis of 2981 patients undergoing AVR with stented bioprostheses (1976-1996).
• Calculation of the EOA/BSA ratio for 2154 patients to define a 'Small' group (<0.75 cm(2)/m(2)) and a control group (>0.75 cm(2)/m(2)).
• Comparison of operative mortality, long-term survival, and freedom from valve-related mortality between groups using Cox regression analysis.

Main Results:

• The 'Small' group (EOA/BSA <0.75 cm(2)/m(2)) experienced higher operative mortality (8% vs. 5%, P=0.03).
• Actuarial survival at 12 years was similar (50% vs. 49%, P=0.27), but freedom from valve-related mortality was significantly lower in the 'Small' group (75% vs. 84%, P=0.004).
• Advanced age and EOA/BSA <0.75 cm(2)/m(2) were predictors of valve-related mortality.

Conclusions:

• Prosthesis-patient mismatch leads to increased early and late mortality following bioprosthetic AVR.
• An EOA/BSA ratio greater than 0.75 cm(2)/m(2) is recommended to avoid obstruction and gradients.
• Careful prosthesis-patient matching is essential for improving survival after AVR.