Subendocardial blood flow in children with congenital aortic stenosis.

Subendocardial blood flow may be estimated from the ratio of flow to the subendocardium to myocardial oxygen consumption. The first may be estimated from the diastolic pressure time index (area between aortic and left ventricular (LV) pressure during diastole) and the latter by the tension time index (integral of LV pressure during systolic ejection). Subendocardial flow index (SEFI) averaged 1.27 (0.96-1.78) in 13 children with normal aortic valves. SEFI averaged 0.88 (0.43-1.65) in asymptomatic children with congenital aortic stenosis and was never greater than 0.9 in symptomatic children. Aortic valve area and systolic pressure difference did not correlate well with symptoms. SEFI and aortic valve area increased in 26 of 28 patients after surgery. However, 23 of 28 had varying degrees of aortic regurgitation following valvotomy. Since calculation of SEFI is not affected by aortic regurgitation, it would appear to be a more useful measure of surgical success than aortic valve area.