HEMODYNAMICS OF ST-JUDE MEDICAL PROSTHESES IN THE SMALL AORTIC ROOT -IN-VIVO STUDIES USING DOBUTAMINE DOPPLER-ECHOCARDIOGRAPHY

Background and aims of the study: The well known correlation between p rosthetic valve orifice area and transvalvular pressure drop has raise d concerns about the presence of significant residual gradients when o nly a small-sized prosthesis can be implanted, particularly in patient s with a large body surface area. The aim of this study was to study t he hemodynamic performance of small-size St. Jude Medical aortic prost heses using dobutamine echocardiography. Methods: Fifteen patients (14 females, one male, of mean age 67 years) who had undergone aortic val ve replacement with size 19 mm St. Jude Medical prostheses at a mean o f 19 +/- 8 (SD) months previously were studied. Dobutamine infusion wa s started at a rate of 5 mu g/kg/min and increased to 10 and subsequen tly to 20 mu g/kg/min at 15-min intervals. Pulsed and continuous-wave Doppler studies were performed at rest and at the end of each stage. E ffective orifice area (EOA) and mean gradient across each prosthesis w ere calculated, and cardiac output (CO) was determined by Doppler meas urement of flow in the left ventricular outflow tract. Results. Dobuta mine-stress increased heart rate and cardiac output by 57% and 86% res pectively (both p<0.0005), and mean transvalvular gradient increased f rom 22.0 +/- 4.9 mmHg at rest to 41.9 +/- 9 mmHg at maximum stress (p< 0.0001). Regression modeling analyses demonstrated that maximum stress gradient was independent of all variables except resting gradient (p= 0.0068). Body surface areas had no effect on the changes in cardiac ou tput, effective orifice area or transprosthetic gradient at maximum st ress. Conclusions: These data demonstrate that the size 19 mm St. Jude Medical prosthesis exhibits favorable hemodynamic performance. Transv alvular gradients remained within a clinically acceptable range, both at rest and under stress conditions. Moreover, in the patient populati on studied, overall hemodynamic performance indicates that with St. Ju de Medical aortic valves, patient-prosthesis mismatch is unlikely to b e a problem of clinical importance.