Hemodynamic performance of the 21-mm Sorin Bicarbon mechanical aortic prostheses using dobutamine Doppler echocardiography

Background. Small-sized mechanical aortic prostheses are commonly associate d with generation of high transvalvular gradients, particularly in patients with large body surface area, and can result in patient-prosthesis mismatc h. This study evaluates the hemodynamic performance of 21-mm Sorin Bicarbon bileaflet mechanical prostheses using dobutamine stress echocardiography. Methods. Fourteen patients (7 women; mean age, 63 +/- 8 years) who had unde rgone aortic valve replacement with a 21-mm Sorin Bicarbon bileaflet mechan ical prosthesis 32.4 +/- 5.1 months previously were studied. After a restin g Doppler echocardiogram, a dobutamine infusion was started at a rate of 5 mug (.) kg(-1 .) min(-1) and increased to 30 mug (.) kg(-1 .) min(-1) at 15 -minute intervals. Pulsed-and continuous-wave Doppler echocardiographic stu dies were performed at rest and at the end of each increment of dobutamine. Both peak and mean velocity and pressure gradient across the prostheses we re measured, and effective orifice area, discharge coefficient, and perform ance index were calculated. Results. Dobutamine stress increased heart rate and cardiac output by 83% a nd 81%, respectively (both p < 0.0001), and mean transvalvular gradient inc reased from 15.6 +/- 5.5 mm Hg at rest to 35.4 +/- 11.9 mm Hg at maximum st ress (p < 0.0001). Although the indexed effective orifice area was signific antly lower in patients with a larger body surface area, this was not assoc iated with any significant pressure gradient. The performance index of this valve was unchanged throughout the study. Regression analyses demonstrated that the mean transvalvular gradient at maximum stress was independent of all variables except resting gradient (p = 0.05). Body surface area had no association with the changes in cardiac output, transvalvular gradient at m aximum stress, and effective orifice area. Conclusions. These data show that the 21-mm Sorin Bicarbon bileaflet mechan ical prosthesis offers an excellent hemodynamic performance with full utili zation of its available orifice when implanted in the aortic position. The lack of significant transvalvular gradient in patients with a larger body s urface area suggests that patient-prosthesis mismatch is highly unlikely wh en this prosthesis is used. (C) 2001 by The Society of Thoracic Surgeons.