RESUMO
BACKGROUND: Aortic prosthetic valves with superior hemodynamic performance are associated with more complete regression of left ventricular hypertrophy and better left ventricular function postoperatively. The near normal function of the pulmonary autografts at rest is well documented, however, exercise data has been seldom reported. The purpose of this study is to evaluate the hemodynamic performance of pulmonary autografts in the aortic position and the homografts used to reconstruct the right ventricular outflow tract during conditions of high cardiac output by means of dobutamine stress echocardiography. METHODS: Between May 1995 and February 1998, 67 patients were submitted to a Ross operation at our institution. Twenty of these patients had a mean age of 28.6+/-8.3 years and a mean follow-up time of 15.7+/-5.9 months. They were studied by dobutamine stress echocardiography to evaluate rest and exercise hemodynamics of the pulmonary autografts as well as of the aortic and pulmonary homografts used to reconstruct the right ventricular outflow tract. Dobutamine infusion was started at 5 microg/kg with incremental doses up to 40 microg/kg in every case. RESULTS: With dobutamine infusion, heart rate increased from 71+/-10 to 142+/-11 beats/min, left ventricular systolic volume from 86.8+/-33.9 mL to 115.9+/-52.6 mL, and cardiac output from 6.3+/-2.9 L/min to 16.8+/-7.4 L/min. Left ventricular function was considered satisfactory at rest and during exercise in all patients. The mean gradient across the autograft increased from 1.03+/-0.95 mmHg to 4.03+/-2.05 mmHg and maximal instantaneous gradient from 2.45+/-2.21 mmHg to 9.54+/-4.85 mmHg. The mean effective orifice area for the autografts were 3.5+/-1.3 cm2 at rest and 3.3+/-1.4 cm2 during exercise. The patients with mild aortic insufficiency at rest had no increase in the degree of regurgitation with exercise. In the right ventricular outflow tract, the mean gradient across the homograft increased from 9.06+/-5.29 mmHg to 17.55+/-9.76 mmHg and maximal instantaneous gradient from 21.4+/-12.5 mmHg to 41.5+/-23.1 mmHg. CONCLUSIONS: Pulmonary autografts exhibit normal hemodynamic performance at rest and during exercise after the Ross operation. However, mild-to-moderate gradients are common at the right ventricular outflow tract and should be carefully monitored.
