Effects of Beta‐Adrenergic Activity on T‐Wave Amplitude

This study addresses the hypothesis that electrocardiographic T‐wave amplitude is influenced by beta‐adrenergic stimulation of the heart. Beta‐adrenergic activity was manipulated both pharmacologically and through behavioral challenge. Under resting conditions, 12 healthy men underwent infusion of placebo and then the beta‐agonist, isoproterenol, and the beta‐blocker, propranolol, in a counterbalanced, crossover design. During infusion of placebo, subjects also underwent two behavioral challenges, a structured interview and mental arithmetic. Analysis of the resting data indicated that propranolol produced a significant increase in T‐wave amplitude, and isoproterenol produced significant T‐wave amplitude attenuation. As previously reported, drug effects were also in evidence for heart rate. Behaviorally‐induced reduction of T‐wave amplitude was observed for mental arithmetic but not structured interview, which again paralleled heart rate data. Both pharmacological and behavioral data reported in this study support the hypothesis that the T‐wave is significantly affected by beta‐sympathetic influence on the heart. However, a nonspecific effect of heart rate change on T‐wave amplitude would also account for these results. The findings are discussed in terms of their implications for the utility of T‐wave amplitude in psychophysiological research.