Effects of enhanced external counterpulsation on carotid circulation in patients with coronary artery disease.

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 beta 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 beta 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 beta 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.

Cyclic GMP release by acute enhanced external counterpulsation.

BACKGROUND: Enhanced external counterpulsation (EECP) is a noninvasive, pneumatic technique that provides favorable effects in patients with coronary artery disease and heart failure. The mechanisms by which EECP exerts its beneficial effects remain poorly understood. Cyclic GMP (cGMP) regulates vascular smooth muscle tone that may improve arterial function. We investigated the effect of a single session of EECP on plasma and platelet cGMP in asymptomatic subjects with cardiovascular risk factors (HCVR) and in patients with coronary artery disease (CAD). METHODS: Fifty-five subjects were included (25 HCVR and 30 CAD) and randomized into two groups to receive either sham (control) or active EECP during 1 h. Plasma and platelet cGMP were measured immediately before and after EECP by radioimmunoassay. RESULTS: One hour of EECP increased cGMP plasma concentration by 52% +/- 66% (SD) (P < .001) and platelet content by 19% +/- 28% (P < .01). The increase in plasma cGMP was particularly marked in CAD patients receiving active EECP (P < .01), mainly in those with low LDL-cholesterol. Platelets, inhibition of nitric oxide synthesis by N(G)-monomethyl-l-arginine (L-NMMA) reduced cGMP by 23% +/- 31% (P < .001), whereas presence of superoxide dismutase and inhibition of phosphodiesterase-5 increased cGMP by 46% +/- 49% and 70% +/- 77%, respectively (P < .001). In all of the cases EECP increased additional platelet cGMP content, which suggests nitric oxide synthase activation. CONCLUSIONS: Acute external counterpulsation showed that very early treatment increases the cGMP production that may participate in the mechanism by which EECP exerts its clinical benefit. Analysis of the modulation of platelet cGMP content suggests that EECP activated the nitric oxide-dependent pathways.