Influence of epinephrine, propranolol, and atrial pacing on spatial distribution of recovery time measured by body surface mapping in congenital long QT syndrome.

Abstract

Sympathetic stimulation plays an important role in the genesis of QT(U) prolongation and ventricular arrhythmias in congenital long QT syndrome (LQTS). Permanent pacemaker as well as beta blockers are reported to be effective in the management of this syndrome. The purpose of this study was to examine influence of epinephrine (alpha- and beta-adrenergic stimulation), propranolol (beta blocker), and atrial pacing on the spatial distribution of repolarization using body surface recovery time (RT) in congenital LQTS. Body surface mapping was recorded in 16 patients with congenital LQTS and 20 control patients before and after epinephrine infusion (0.1 microg/kg per min), oral propranolol (1 to 2 mg/kg per day), addition of epinephrine during oral propranolol, atrial pacing at a cycle length of 600 or 750 msec, and addition of epinephrine during atrial pacing. The RT, that is, the interval between the QRS onset and the maximum dV/dt point in the ST-T segment, was measured automatically by a computer from each of the 87 mapping leads, and the corrected RT (RTc) was calculated using Bazett's method. In patients with congenital LQTS, epinephrine markedly changed the T(U) wave morphology and spatial distribution of RT, especially the distribution of maximum RT of the left anterior chest and back. Epinephrine prolonged the maximum RTc and the minimum RTc in 87 leads and increased the RTc dispersion (difference between maximum and minimum RTc in each patient). Neither propranolol nor atrial pacing changed the T(U) wave morphology, spatial distribution of RT, or any RTc parameters at rest. Propranolol prevented the influences of epinephrine on the T(U) wave morphology, spatial distribution of RT, and RTc parameters, whereas atrial pacing did not. In control patients, marked changes of the T(U) wave morphology and RTc parameters were not recognized during the entire protocol. Our results indicate that epinephrine markedly changes the spatial distribution of repolarization and increases the dispersion of repolarization, which probably are linked to arrhythmogenesis in congenital LQTS. The data suggest that propranolol but not atrial pacing are effective to suppress repolarization abnormalities during sympathetic stimulation.