THE EFFECT OF TRANSCUTANEOUS ELECTRICAL NERVE-STIMULATION ON CORONARYAND SYSTEMIC HEMODYNAMICS IN SYNDROME-X

Background Neurostimulation techniques have been shown to be beneficia l in patients with angina and syndrome X but the mechanism remains unc lear, We examined the effect of transcutaneous electrical nerve stimul ation (TENS) on coronary artery blood flow in a group of patients with syndrome X. Methods Coronary blood flows were measured in 11 patients with angiographically normal coronary arteries, positive results from exercise tests and angina (syndrome X) using intracoronary Doppler ca theters combined with quantitative coronary angiography. Results The m ean coronary flow velocity did not increase in any patient during TENS therapy; in fact, there was a fall from 5.2+/-2.8 to 4.3+/-1.9 cm/s ( P=0.02) and the coronary blood flow index fell from 47+/-22 to 38+/-16 cm/s per mm(2) (P=0.007). This was associated with a fall in the rate x pressure product from 0.92+/-0.22 to 0.83+/-0.18 mmHg/min (P=0.038) . The coronary vascular resistance rose from 2.4+/-1.1 to 3.0+/-1.6 mm Hg/cm per s per mm(2) (P=0.041). There were no major changes in the ep icardial coronary artery diameter during TENS and there was no signifi cant effect on the response to the cold-presser test. Conclusions In t his group of patients with syndrome X, TENS produced a small but signi ficant fall in coronary artery blood flow associated with a reduction in the rate X pressure product. TENS had no significant effect on coro nary vasomotion during sympathetic stimulation by the cold-presser tes t. Thus, TENS is unlikely to have a direct effect on coronary artery v asomotion or haemodynamics in syndrome X but reduces the rate X pressu re product and thus myocardial oxygen consumption.