Echocardiographic changes in the thickness of porcine valves with time.

To assess the ability of M-mode echocardiography to detect the incidence and frequency of porcine xenograft valve thickening, echocardiograms were obtained in 147 mitral and aortic porcine xenograft valves implanted in 131 patients. The patients were divided into an early group in whom the echocardiograms were performed within two months of valve replacement, and intermediate group studied two to 48 months after surgery, and a late group 48 months or longer after surgery. The porcine cusp echoes were visualized with proper gain settings, enlarged, and then recorded on a strip chart. The mean thickness of both the mitral and the aortic cusps was measured with the valve in the coapted position. The mean thickness of the porcine mitral valve increased from 1.23 +/- 0.12 in the early group to 2.3 mm +/- 0.19 in the late group (P less than .02). Aortic valve thickness increased from 0.91 mm +/- 0.07 in the early group to 2.1 mm +/- 0.37 (P less than .05) in the late group. A significant change in valve thickness was not observed in the intermediate group. In the late group of valves, 21/82 (27 percent) had a thickness greater than 3 mm. Nine of these valves (43 percent) have required replacement because of clinical dysfunction. Only 1.6 percent (1/61) of the valves in the late group with a thickness of less than 3 mm had or developed severe porcine valve insufficiency (P less than 0.001). In all ten instances, the echocardiographic assessment of valve thickness was validated on gross examination of the valve removed at surgery. This study indicates that the thickness of both mitral and aortic porcine valves can be measured by M-mode echocardiography. Valve thickness increases after 48 months and those valves with thickening of 3 mm or more are at a higher risk of developing clinical evidence of valve dysfunction.