PREDICTION OF POSTOPERATIVE EXERCISE TOLERANCE AFTER AORTIC-VALVE REPLACEMENT

Valve size selection for aortic valve replacement is still a controver sial matter, particularly in patients with small aortic annuli. To ass ess 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 replacemen t with a St. Jude Medical valve. This assessment was carried out at a mean of 2.2 years postoperatively using ergometer exercise testing. Th ese levels were evaluated as a measure of the percentage of predicted. At rest, there was no significant correlation between the predicted p eak oxygen consumption and the pressure gradients across the prosthese s, as measured by Doppler ultrasound. In 18 patients with aortic regur gitation, the preoperative dimensions of the left ventricle in end-dia stole and end-systole correlated inversely (p < 0.05) with the percent age of predicted peak oxygen consumption. In 21 patients with aortic s tenosis, the linear regression line (p < 0.01) was derived from the co rrelation between the percentage of predicted peak oxygen consumption and the valve area index (geometric valve orifice area/body surface ar ea). We conclude that the preoperative end-systolic and end-diastolic dimensions should be less than 50 mm and 70 mm, respectively, in the s etting of aortic regurgitation, and a valve area index, though it prov ed to be weakly correlated with the percentage of the peak oxygen upta ke, should probably be more than 1.5 cm(2)/m(2) in the setting of aort ic stenosis to achieve good exercise capacity postoperatively (> 80% o f predicted peak oxygen consumption).