Effects of isoproterenol on T-wave amplitude and heart rate: a dose-response study.
This report examines the hypothesis that electrocardiographic T-wave amplitude is sensitive to graded increases in beta-sympathetic stimulation of the heart. Beta-adrenergic activity was manipulated pharmacologically in 9 healthy men by bolus infusion of isoproterenol in each of six doses: 0.1, 0.25, 0.5, 1.0, 2.0, and 4.0 micrograms. Results indicated that elevations in heart rate above placebo values increased as a linear function of isoproterenol dose. In contrast, the dose-response curve for T-wave amplitude was best described by a quadratic function: an initial reduction in T-wave amplitude at low levels of isoproterenol infusion was followed by a significant reversal of this effect at higher doses. Comparison of the heart rate and T-wave amplitude data points to limitations in the use of the latter as an index of beta-adrenergic activity. One of several possible explanations for the T-wave results would entail a mechanism that preserves ventricular function at high levels of beta-sympathetic stimulation.
Contrada
R J
RJ
Department of Psychology, Rutgers-The State University, New Brunswick, New Jersey 08903.
Dimsdale
J
J
Levy
L
L
Weiss
T
T
D000328:Adult; D004305:Dose-Response Relationship, Drug; D004562:Electrocardiography / Q000187:drug effects*; D006321:Heart / Q000294:innervation; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology*; D008297:Male; D011943:Receptors, Adrenergic, beta / Q000187:drug effects
D011943:Receptors, Adrenergic, beta; D007545:Isoproterenol