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

T he 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,s-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. The patient group consisted of 34 children and adolescents (aged 3 months to 24 years [mean f SD 10.5 f 6.4 years, median 111) with isolated valvar AS who underwent cardiac catheterization at our institution between 1985 and 1990. Their weights ranged from 6.8 to 105 kg (mean 43.5 f 27.5). Peak systolic AS gradient at rest in these children rangedfrom I3 to 109 mm Hg, and the degree of aortic regurgitation ranged from 0 to 3+ (on a 0 to 4+ scale). Twenty children had native valvar AS (i.e., noprior treatment) and 14 children had undergone prior balloon valvuloplasty. No children with prior surgical valvotomy were included in this study. Cardiac catheterization was performed percutaneously after light sedation with morphine sulfate and chloral hydrate. Complete rightand left-sided cardiac catheterization was performed, and cardiac output was measured in triplicate using the thermodilution technique. The left-sided pressures were recorded using 2 identical 4 to 7 Fr pigtail catheters (UMI, Ballston Spa, New York) and fluid-filled transducers (Sorenson, No. Chicago, Illinois). In each patient both pigtail catheters were initially positioned side-by-side in the descending aorta to confirm that identical waveforms were recorded.