Aortic valve replacement with a small valve prosthesis: a review of clinical and echocardiographic studies for impact of prosthesis-patient mismatch

Aortic valve replacement (AVR) has become standard therapy for treating diseases of the aortic valve. However, the selection of a prosthetic valve is considered to be an important factor determining postoperative recovery of cardiac function and quality of life, because the use of small valve prostheses may cause residual obstruction to left ventricular outflow. The situation in which "the effective prosthetic valve area, after insertion into the patient, is less than that of a normal human valve," has been described as "prosthesis-patient mismatch (PPM)." The most commonly used measure of PPM is the valve effective orifice area indexed to body surface area (EOAI), and PPM is generally defined as EOAI < or =0.85cm(2)/m(2). In this paper, we review clinical and echocardiographic studies of small valve prostheses in the aortic position to investigate the clinical impacts of PPM on short- and long-term outcomes after AVR. Some studies have shown decreased symptom resolution, poor regression of left ventricular mass, or decreased survival with an EOAI < or =0.85cm(2)/m(2), while others have observed no adverse effects of PPM on short- and long-term results of AVR. Therefore, even in Western countries, in studies involving large numbers of patients, conclusions drawn concerning the impact of PPM differ greatly among reports. In conclusion, it is desirable to examine in detail, in many patients, whether the use of prosthetic valves with EOAI < or =0.85cm(2)/m(2) is also a risk factor for poor prognosis in Japanese patients, whose body size is in general smaller than that of Western patients.