Effects of Enhanced External Counterpulsation on Carotid Circulation in Patients with Coronary Artery Disease

Abstract

Background: Enhanced external counterpulsation (EECP) is a noninvasive method previously shown to improve measures of myocardial ischemia in patients with coronary artery disease. However, the concomitant effects of EECP on large and small arterial properties have been poorly examined. In a randomized controlled study, we investigated whether arterial stiffness and resistance of the carotid circulation are altered by EECP. Methods: Thirty patients with angiographically demonstrated coronary artery disease were randomized into two groups to receive either ‘sham’ or active EECP therapy for 35 1-hour sessions. The β stiffness index was calculated by the ln(Ps/Pd)/DD equation where Ps and Pd = systolic and diastolic blood pressure, and DD = the ratio between carotid pulse and diastolic diameter, measured by ultrasound sequential frames during the cardiac cycle. Carotid vascular resistance was calculated as the ratio between mean arterial pressure and mean common carotid blood flow. Results: No significant between-group differences were seen in clinical characteristics or carotid hemodynamics at baseline. The β stiffness index and carotid vascular resistance were significantly reduced after 35 h of active EECP (p < 0.01), and the decrease was significantly different when compared with controls (p < 0.05 for β stiffness index and p < 0.001 for carotid vascular resistance). These reductions persisted after multiple covariate adjustment. Conclusions: This study suggests that EECP exerts clear arterial effects on large and small vessels of the carotid circulation. The combined effects on arterial stiffness and vascular resistance are of particular interest in cardiovascular disease involving reduction in blood flow, in which techniques that increase regional blood flow may be beneficial.