Prediction of postoperative exercise tolerance after aortic valve replacement

Abstract

Valve size selection for aortic valve replacement is still a controversial matter, particularly in patients with small aortic annuli. To assess optimal valve size, exercise capacity, as measured by peak oxygen consumption levels, was determined in 39 patients (age range, 18 to 77 years; mean, 56 years) who underwent isolated aortic valve replacement with a St. Jude Medical valve. This assessment was carried out at a mean of 2.2 years post-operatively using ergometer exercise testing. These levels were evaluated as a measure of the percentage of predicted. At rest, there was no significant correlation between the predicted peak oxygen consumption and the pressure gradients across the prostheses, as measured by Doppler ultrasound. In 18 patients with aortic regurgitation, the preoperative dimensions of the left ventricle in end-diastole and end-systole correlated inversely ( p < 0.05) with the percentage of predicted peak oxygen consumption. In 21 patients with aortic stenosis, the linear regression line ( p < 0.01) was derived from the correlation between the percentage of predicted peak oxygen consumption and the valve area index (geometric valve orifice area/body surface area). We conclude that the preoperative end-systolic and end-diastolic dimensions should be less than 50 mm and 70 mm, respectively, in the setting of aortic regurgitation, and a valve area index, though it proved to be weakly correlated with the percentage of the peak oxygen uptake, should probably be more than 1.5 cm 2/m 2 in the setting of aortic stenosis to achieve good exercise capacity postoperatively (>80% of predicted peak oxygen consumption).