ABNORMALITIES IN VENTRICULAR ACTIVATION AND REPOLARIZATION IN SICKLE CELL DISEASE AND NORMAL SIBLINGS

Abstract

Prolongation of the QTc interval can result from lengthening of ventricular activation and/or repolarization due to ischemia. Although we have previously reported exercise induced ischemic-like ST depression in children with sickle cell disease, the response of the QT interval to exercise has not been reported. We studied 68 children with various hemoglobinopathies including hemoglobin (Hgb) SS (sickle cell) disease (n=36), Hgb AS (n=15), Hgb SC (n=12) and Hgb AC (n=5) during upright cycle ergometry. Siblings (n=20) of patients with Hgb SS, who had normal Hgb, were also evaluated. The QT interval was measured at rest (R) and peak exercise (PE), and then corrected for heart rate with Bazett's Formula. These results were compared to those of 48 normal (NL) children (Hgb AA). All patients has a normal QRS duration (<0.08 sec.). (*P<0.001 vs. NL)At Both rest and peak exercise, patients with a hemoglobinopathy had prolongation of their QTc interval as compared to normal. Siblings of patients with Hgb SS, who had NL Hgb, also demonstrated QTc prolongation. We conclude that there are abnormalities of ventricular activation/repolarization suggestive of ischemia in patients with sickle cell disease and their normal family members which are independent of hemoglobin type.