Tasca G et al. (2006) Impact of prosthesis–patient mismatch on cardiac events and midterm mortality after aortic valve replacement in patients with pure aortic stenosis. Circulation 113: 570–576

Prosthesis–patient mismatch (PPM) occurs when a prosthetic aortic valve with a smaller effective orifice area (EOA) than that of the patient's native valve is implanted. PPM results in abnormally high transvalvular pressure gradients, but it is unclear whether postoperative survival is affected. Tasca et al. investigated the effect of PPM, defined as an INDEXED EOA, on overall out-of-hospital mortality and cardiac events after aortic valve replacement (AVR).

The study included 315 patients who underwent AVR for pure aortic stenosis at a hospital in Brescia, Italy, from September 1997 to September 2003. Follow-up visits at 3 months and annual telephone interviews were used to investigate mortality and cardiac events (cardiac death, sudden death, hospital readmission for angina, heart failure or syncope). Mean follow-up was 3.7 ± 1.7 years.

PPM occurred in 47% of patients. Patients with PPM were older, had higher body surface area, had a higher BMI and were more likely to be female than patients without PPM (P <0.001, P = 0.007, P <0.001 and P = 0.003, respectively). More deaths occurred in the PPM group than in the non-PPM group (23 vs 6 deaths; P = 0.003), and PPM patients were also more likely to experience a cardiac event (30 vs 11 patients; P = 0.006).

The authors conclude that PPM has strong predictive value in terms of mortality and cardiac event risk in patients with pure aortic stenosis undergoing AVR. They note that these risks could be reduced substantially by estimating indexed EOA before prosthesis implantation.