Subvalvular gradients in patients with valvular aortic stenosis: prevalence, magnitude, and physiological importance.

BACKGROUND Although subvalvular gradients in patients with aortic stenosis have been described, their behavior and response to exercise have not been well characterized. METHODS AND RESULTS Left ventricular and aortic pressures and linear flow velocity were measured with a catheter-tip manometer at rest and during supine exercise in 27 patients with valvular aortic stenosis. A subvalvular gradient was measured in each patient that represented, on average, 48% of the total resting transvalvular gradient. With exercise, both total (rest: 80+/-26 mm Hg; exercise: 90+/-25 mm Hg) and subvalvular gradients (rest: 37+/-13 mm Hg; exercise: 60+/-22 mm Hg) increased significantly. There was a significant inverse relationship between change in exercise cardiac output and total and subvalvular gradients. However, only the exercise subvalvular gradient predicted cardiac output response. CONCLUSIONS Subvalvular pressure gradients are universally present in patients with severe aortic stenosis and comprise approximately half of the total transvalvular gradient. The extent of exercise cardiac output increase is inversely related to the subvalvular gradient magnitude.