Update on aortic valve prosthesis-patient mismatch in Japan.

The influence of aortic valve prosthesis-patient mismatch (VP-PM) on the clinical outcome has been an ongoing controversy. The reported prevalence of VP-PM after aortic valve replacement (AVR) ranges widely between 20 and 70 %. The inconsistent impact of VP-PM on short-term and long-term mortality, regression of left ventricular (LV) hypertrophy, and exercise capacity may be explained by differences of the patient populations, the definition of VP-PM, and the use of different prostheses. Moreover, many factors other than the severity of VP-PM should be taken into account when considering its impact on individual patients after AVR. Although the concept of VP-PM is easy to understand, it cannot be applied to the whole patient population. In Japan, the age of the candidates for AVR has increased markedly in recent years, but almost all elderly patients with a small BSA (<1.6 m(2)) have received newer-generation prostheses with a small outer diameter and large effective orifice area. Indeed, previous studies of Japanese patients have demonstrated that VP-PM was no more than moderate in most cases and its impact on clinical outcomes was generally acceptable. Although severe VP-PM is infrequent and its clinical implications are still unproven in elderly Japanese patients, it would seem reasonable to try to prevent severe VP-PM. Thus, VP-PM itself cannot be accepted as an independent risk factor in Japanese patients, but the useful preventive strategies for severe VP-PM in inactive very elderly persons remain controversial. The implantation of newer-generation biological or mechanical prostheses with or without aortic annular enlargement should be considered according to the characteristics of the patient and the risk-benefit ratio for carrying out a particular procedure in an individual patient.