THE TELEMETERED EXERCISE ELECTROCARDIOGRAM IN CONGENITAL AORTIC STENOSIS

Abstract

Since children with aortic valve stenosis, who are at risk of syncope or sudden death, cannot be identified by the resting electrocardiogram or vectorcardiogram, the exercise electrocardiogram was evaluated and compared with the hemodynamic data obtained during cardiac catheterization. Telemetered exercise electrocardiograms were obtained in 31 children, ages 8 to 18 years, with aortic valve stenosis and in 25 normal children of comparable age. Electrocardiographic leads V1, V₅, and V₆ were obtained prior to, during, and following exercise on a variable resistance bicycle ergometer. Subjects pedalled until a heart rate of 170 per minute or greater was attained and maintained for at least 2 minutes. An increase in T-wave amplitude was observed in both control children and in those with aortic stenosis. No S-T segment abnormalities were noted in the normal children. Of the 16 patients with peak systolic left ventricular to aortic pressure gradients of less than 50 mm Hg, only one showed a segmental S-T depression. Of the 15 children with aortic valve gradients of 50 to 100 mm Hg, however, all except one showed an S-T segment depression in lead V5 of 2 mm or greater.

No correlation between the resting electrocardiogram or the vectorcardiogram and the aortic valve gradient or left ventricular peak systolic pressure could be made. In addition, the abnormal S-T segment response to exercise could not be predicted from or correlated with the resting electrocardiogram. Since an ischemic S-T segment response to exercise was found uniformly in those with the higher gradients, this test appears to have a high degree of specificity in the clinical evaluation of these patients.