DYNAMIC EVALUATION OF THE 21-MM MEDTRONIC INTACT AORTIC BIOPROSTHESISBY DOBUTAMINE ECHOCARDIOGRAPHY

Background. High residual transvalvular gradients have been reported w ith the use of small Medtronic Intact aortic valve prostheses. The aim of this study was to evaluate the hemodynamic performance of 21-mm pr ostheses using dobutamine Doppler echocardiography. Methods. Ten patie nts (7 women; mean age, 79 years) who had undergone aortic valve repla cement with 21-mm Medtronic Intact prostheses 19.1 +/- 9.9 (standard d eviation) months previously were studied. Dobutamine infusion was star ted at a rate of 5 mu g.kg(-1).min(-1) and increased to 10 and 20 mu g .kg(-1).min(-1) at 15-minute intervals. Pulsed and continuous-wave Dop pler studies were performed at rest and at the end of each stage. Effe ctive orifice area, performance index, and discharge coefficient of ea ch valve were calculated, and peak and mean velocity and pressure drop across the prostheses were measured. Cardiac output was determined by Doppler measurement of now in the left ventricular outflow tract. Res ults. Dobutamine stress increased heart rate and cardiac output by 68% and 65%, respectively (both p < 0.005), and mean transvalvular gradie nt increased from 19.1 +/- 5.1 mm Hg at rest to 33.2 +/- 7.7 mm Hg at maximum stress (p < 0.0001). Regression analyses demonstrated that max imum-stress gradient was independent of all variables except resting g radients (p < 0.004). Body surface area had no effect on the changes i n cardiac output, effective orifice area, or transprosthetic gradient at maximum stress. Conclusions. These data show that the 21-mm Medtron ic Intact aortic prosthesis exhibits acceptable hemodynamic performanc e. Transvalvular gradients remained within a clinically acceptable ran ge, both at rest and at maximum stress. Moreover, overall hemodynamic performance suggests that patient-prosthesis mismatch is unlikely to b e a problem of clinical importance when this prosthesis is used. (C) 1 997 by The Society of Thoracic Surgeons.