Hemodynamic determinants of the peak systolic left ventricular-aortic pressure gradient in children with valvar aortic stenosis

Abstract

The peak systolic pressure gradient (the difference between peak left ventricular [LV] and peak aortic systolic pressures) has been used for many years as a primary measure of severity in children with valvar aortic stenosis (AS).1-3 Reliance on the peak systolic pressure gradient in clinical decision-making was based on the practice of measuring the gradient at catheterization by withdrawing a single catheter from the left ventricle to aorta. In recent years it has become common, however, to measure LV and aortic pressures simultaneously with dual catheter techniques.4 The time-honored peak systolic gradient does not actually exist in time, because peak LV pressure in AS occurs well before peak aortic systolic pressure. The pressure gradients that actually exist in real time between the left ventricle and aorta (the instantaneous gradients) vary throughout systole. These instantaneous pressure gradients, which include peak instantaneous gradient and mean systolic gradient (the integral of the systolic instantaneous gradients) can be estimated noninvasively,5-7 unlike peak systolic gradient. Nevertheless, clinicians continue to rely on peak systolic pressure gradient as an important index of severity for clinical decision-making in children with valvar AS. The purpose of this study was to define, at cardiac catheterization, the relation between peak, mean and peak instantaneous systolic pressure gradients in children with valvar AS.