A simplified method for calculating wall stress in infants and children.

Measurement of the end-systolic wall stress-mean velocity of circumferential fiber-shortening relation, a load-independent measure of contractility, has enabled cardiologists to assess ventricular function under various loading conditions and at different heart rates. Unfortunately, it is time-consuming and difficult to perform in routine pediatric practice. Because a close relationship was noted between end-systolic pressure and mean blood pressure, we estimated wall stress by mean blood pressure in 115 patients. There was an excellent correlation between end-systolic blood pressure and mean arterial pressure (r = 0.84) and end-systolic wall stress and mean systolic wall stress (r = 0.98). The difference in mean blood pressure was 5.1 mm Hg (95% confidence interval-10.5 to 20.6 mm Hg), and the difference in mean wall stress was 2.7 gm/cm2 (95% confidence interval-2.0 to 3.8 gm/cm2). More important, substitution of mean blood pressure for end-systolic pressure allowed accurate identification of patients with normal contractility (55/56) and abnormal contractility (57/59).