Transcutaneous electrical nerve stimulation induces vasodilation in healthy controls but not in refractory angina patients.

Abstract

Transcutaneous electrical nerve stimulation (TENS) is an effective treatment option to relieve ischemic pain in refractory angina pectoris (RAP). In healthy persons, TENS enhances local blood flow, but the mechanism responsible for the anti-ischemic effect in RAP seems to be different. The aim of the present investigation was to compare the difference in blood flow and vasodilatory response to TENS between angina patients and healthy controls and evaluate how vascular response in these groups is affected by amperage dosage above and below motor threshold levels. Our study evaluated upper limb vascular responses to low- and high-dose TENS (below and above motor threshold) in RAP patients compared with healthy controls. TENS was applied on the nondominating forearm. Forearm blood flow (FBF) was measured by venous occlusion plethysmography. Forearm vascular resistance (FVR) was determined (mean arterial pressure [MAP]/FBF). Measurements were done during baseline, low-dose TENS, high-dose TENS, and during recovery. A significant dose-dependent increase in FBF in response to TENS stimulation was seen in controls (n=18) but not in RAP (n=23) (P=0.008). There was no significant difference in FVR ratio (FVR(stim)/FVR(ctrl)) between control (n=7) and RAP (n=23) groups at low dose (controls, 5.7+/-21%; RAP, 9.7+/-20%) or recovery (controls, -4.6+19%; RAP, 5.9+25%). High-dose TENS resulted in a significantly reduced FVR ratio (-16.8+/-11%) in controls (n=7) compared with RAP (1.6+/-32%, n=23) (P=0.02). High-dose TENS induces forearm vasodilation in healthy subjects but not in patients with RAP. These findings suggest that TENS has different vascular effects in patients with severe coronary artery disease compared with healthy controls.