Dobutamine stress echocardiography and left ventricular mass changes of mechanical aortic valve replacement in four years follow-up

Aim. The aim of this study was to investigate the differences in cardiac response to stress according to the size of the prosthetic valve in patients who underwent aortic valve replacement (AVR) and to evaluate the relationship between the size of the prosthetic valve and cardiac recovery-remodeling after the operation. Methods. Thirty patients who had undergone AVR (12 patients) or double valve replacement (18 patients) underwent dobutamine-stress echocardiography 4.2 years after the operation to evaluate response to stress . They were divided into 2 groups according to valve prosthesis size. The small-size AVR group (group 1, n=17) had prosthetic aortic valves £21 mm; the large-size AVR group (group 2, n=13) had valves >21 mm. Response to stress and preoperative and postoperative echocardiographic findings were compared. Pulsed and continuous-wave Doppler studies were performed at rest and at the end of each stage. Peak and mean aortic gradients, left ventricular diastolic and systolic functions were measured for each group. Results. Dobutamine stress increased heart rate and blood pressure in both groups. Peak pressure gradient across the aortic valve prostheses was 42.1 mm Hg in group 1 and 20.9 mm Hg in group 2 (P<0.05) at rest. After dobutamine infusion, the peak pressure gradient across the aortic valve prostheses increased to 85.1 mm Hg in group 1 and 54 mm Hg in group 2 (P<0.05). Isovolumetric relaxation time returned to normal in both groups following dobutamine infusion; this decrease was significant only in group 1. Patients achieved a decrease in left atrium and left ventricular diameters and volumes, as evidence of remodeling following AVR. Left ventricular mass index (LVMI) decreased from 127.6±47.6 to 98.1±36.9 and from 159.9±16.1 to 125.3±10.1 in groups 1 and 2, respectively, but this decline was not statistically significant. Conclusion. Smaller valves have higher gradients and this significant difference increases under stress. Significant improvement in echocardiographic diameters, cardiac filling volumes and LVMI reflects the benefit of the operation. Cardiac remodeling is independent of valve size, although high transprosthetic gradients occur during stress conditions.