Catecholamine metabolism during pacing-induced angina pectoris and the effect of transcutaneous electrical nerve stimulation

Abstract

The arterial levels of norepinephrine and epinephrine were estimated in 14 patients with severe coronary artery disease in order to assess the catecholamine metabolism during pacing-induced angina pectoris and to evaluate the effects of transcutaneous electrical nerve stimulation (TENS). Arterial levels of epinephrine and norepinephrine increased significantly during pacing to angina pectoris ( p < 0.05 and p < 0.001, respectively), indicating that maximal atrial pacing induced an increase in sympathetic tone. At the corresponding pacing rate during TENS, myocardial lactate production was improved ( p < 0.01) and the ST segment depression was less pronounced ( p < 0.05). The maximal pacing rate during TENS was 141 ± 24 compared to 123 ± 19 ( p < 0.01) and the heart rate-blood pressure product was also significantly higher ( p < 0.01), suggesting an elevation of the anginal threshold by TENS. Systemic vascular resistance and systolic blood pressure were significantly reduced (both p < 0.01). These beneficial results may be caused by a decrease in left ventricular afterload as reflected by a fall in systolic blood pressure and may be explained by reduced sympathetic activity. TENS may decrease the sympathetic activity either directly or indirectly as a consequence of pain inhibition. This hypothesis is supported by the fact that arterial levels of epinephrine and norepinephrine dropped during TENS in TENS responders.