Validation of applications of indexed aortic prosthetic valve areas calculated by Doppler echocardiography

Abstract

Doppler echocardiographic evaluation of aortic valve prostheses is based on the use of variables heretofore validated mostly for native valves. Accordingly, this study examined the validity and relative usefulness of the Doppler valve gradient and area measurements in 31 patients (mean age 69 ± 10 years) 20 ± 4 months after implantation of a given type of aortic bioprosthesis ranging in size from 19 to 29 mm.Valve area data obtained with both the standard and simplified continuity equations were compared with known in vitro prosthetic valve area measurements and an excellent correlation was obtained between the standard and simplified continuity equations (r = 0.98, SEE ± 0.07 cm2, p < 0.0095) and between in vivo and known in vitro prosthetic valve areas (r = 0.86, SEE ±0.16 cm2, p < 0.0005). Peak gradient ranged from 10.8 to 75.0 mm Hg (mean 35 ± 16) and mean gradient from 7.6 to 43.7 mm Hg (mean 20.5 ± 9.5). The correlations between prosthetic valve gradient and in vivo area were r = −0.53, SEE ±14 mm Hg and r = −0.49, SEE ±8.63 mm Hg for peak and mean gradient, respectively. These relations were improved by indexing valve area by body surface area. The best correlations were obtained between indexed valve area and a quadratic function of the gradient (r = −0.72, SEE ±11.72 mm Hg and r = −0.70, SEE ±7.28 mm Hg for peak and mean gradient, respectively), reflecting a curvlrelation.This study validates the use of either the standard or the simplified continuity equation for the noninvasive Doppler echocardiographic assessment of intrinsic aortic bloprosthesis performance. Peak and mean valve gradient data are less useful because they depend on cardiac output, which increases with body size. The exponential relation demonstrated between pressure gradient and indexed prosthetic valve area may allow the formulation of preoperative guidelines to avoid mismatch between prosthesis size and body size.