Hemodynamic Evaluation of St. Jude Medical Aortic Valve Prostheses Using Dobutamine Stress Echocardiography

Background: Small-sized mechanical aortic prostheses are proposed to be associated with high trans-prosthetic gradients and consequent patient-prosthesis mismatch. This study aimed to assess the hemodynamic performance of patients with St. Jude aortic mechanical prostheses of various sizes. Methods: Dobutamine infusion was performed in 39 patients with three different sizes of St. Jude Medical aortic prostheses. A graded infusion of dobutamine was administered at increments of 5, 10, and 20 µg/kg/min at 15-minute intervals. Pulse-wave and continuous-wave Doppler echocardiograms were performed at rest and stress. Hemodynamic parameters were measured and calculated. Results: In response to dobutamine infusion, mean blood pressure, heart rate and cardiac output were increased by 14%, 50%, and 52%, respectively, at maximum stress. Dobutamine stress produced a similar increase in cardiac output in patients with 21-, 23-, and 25-mm, aortic prostheses. Peak trans-prosthetic pressure gradient of 21-, 23-, and 25-mm prostheses increased from 32.7±12.3, 23.8±5.9, and 20.6±5.8mm Hg, respectively, at rest to 75.3±20.3, 57.2±23.1, and 51.2±20.8 mm Hg, respectively, at maximum stress. Using one-way ANOVA, significantly higher peak trans-prosthectic pressure gradient was shown in 21-mm aortic prostheses at rest and maximum stress (p = 0.004, and 0.03 respectively). Effective orifice area index, discharge coefficient, and performance index were comparable in the three valve sizes at rest and maximum stress (all p values ＞ 0.05). Conclusions: St. Jude Medical 21-mm prosheses carriers had higher peak trans-prosthetic pressure gradients at rest and stress but had comparable effective orifice area and effective orifice area index.