Improved prediction of peak left ventricular pressure by echocardiography in children with aortic stenosis

Prediction of peak left ventricular pressure by echocardiography in children with aortic stenosis assumes that wall stress is normal. The recent finding that stress is subnormal in many children with aortic stenosis and elevated ejection performance requires reevaluation of this noninvasive technique. By using M-mode echocardiography, left ventricular end-diastolic dimension and wall thickness and left ventricular shortening fraction were measured in 27 children with aortic stenosis undergoing left ventricular pressure measurement by cardiac catheterization. Similar echocardiographic measurements and systolic blood pressure determinations by the cuff method were obtained from 29 normal children.Peak circumferential wall stress and shortening fraction were calculated from the echocardiographic and pressure data. It was found that stress was inversely proportional to shortening fraction for all patients with aortic stenosis (p < 0.001, r = −0.86). In a subgroup of patients with a shortening fraction of less than 0.40, stress was 262 ± 20 mm Hg, similar to 280 ± 30 mm Hg in the normal group but greater than 205 ± 27 mm Hg in patients with a shortening fraction of 0.40 or greater (p < 0.001). In patients with aortic stenosis, the ratio of left ventricular end-diastolic wall thickness to cavity dimension predicted peak left ventricular pressure moderately well (r = 0.83, standard error of the estimate [SEE] = 23). The stress-shortening fraction relation was used to estimate stress and correct this ratio in patients with diminshed stress and a shortening fraction greater than or equal to 0.40. This yielded a significantly improved correlation (r = 0.93, SEE = 15, p < 0.05). It is concluded that echocardiographic prediction of peak left ventricular pressure should include correction for diminished wall stress in children with an elevated ejection performance.