Changes in arterial levels and myocardial metabolism of catecholamines during pacing-induced angina pectoris.

In order to elucidate the effects of atrial pacing on cardiac catecholamine metabolism, 11 patients were studied during cardiac catheterization. Blood samples were drawn from a peripheral artery and the coronary sinus for estimation of catecholamine concentrations. Heart rate was increased by 10 beats/min each minute, and all patients experienced chest pain at maximal pacing rate. Coronary sinus blood flow rose from 122 +/- 19 at rest to 208 +/- 25 ml/min at final pacing rate, and myocardial lactate extraction ratio decreased. There was no significant change in arterial epinephrine levels, whereas the extraction ratio decreased (p less than 0.05). The norepinephrine arterial levels increased at the final pacing rate (p less than 0.01). The calculated myocardial release increased as well, but not to a statistically significant degree. The exact mechanisms of the rise in sympathetic activity and arterial norepinephrine levels cannot be ascertained with the present study design. Myocardial ischemia with subsequent chest pain seems to be a probably cause for the increased sympathetic outflow.