Enhanced external counterpulsation improves endothelium-dependent vasorelaxation in the carotid arteries of hypercholesterolemic pigs

Background Enhanced external counterpulsation (EECP) has been demonstrated to be an effective method for the treatment of atherosclerotic vascular disease. However, the exact mechanism underlying the beneficial effects of EECP is not completely clear. We hypothesized that EECP leads to improvement in endothelial function, contributing to its clinical benefits. Methods Fifteen male domestic pigs were initially divided into 2 dietary groups: one consumed a normal feeding (NF) of pig chow (n = 5), and one consumed a high-fat (HF) pig chow (n = 10). After 8 weeks on the NF or HF diet, 5 HF pigs received EECP treatment (HF + EECP) 1 h daily for 6 weeks and the remaining 5 HF pigs continued to be fed by high cholesterol diet. At the end of 6-week EECP treatment, the carotid arterial rings from all of the pigs were harvested. Endothelium-dependent and -independent vasorelaxation to acetylcholine (ACh) and sodium nitroprusside (SNP) were measured in a dose-dependent manner. Results The high fat diet resulted in increase in plasma cholesterol and triglyceride levels (p < 0.05). Endothelium-dependent vasorelaxation was decreased in the HF group compared to the NF control (p < 0.05). However, EECP treatment partially improved impaired endothelium-dependent vasorelaxation in the HF + EECP group compared to the HF control (p < 0.05). Endothelium-independent vasorelaxation was not significantly different among the three groups. Conclusions Endothelium-dependent vasorelaxation is impaired in the hypercholesterolemic pigs. EECP treatment significantly improves hypercholesterolemia-induced diminished endothelium-dependent vasorelaxation. It suggests that amelioration in endothelial function may at least in part contribute to the beneficial effects of EECP treatment in clinical practice.