Acute and chronic hemodynamic effects of enhanced external counterpulsation in patients with angina pectoris

Background: Enhanced external counterpulsation (EECP) is an effective noninvasive treatment for patients with angina pectoris. However, the hemodynamic effects of EECP are still unknown and have been theorized to simulate the clinical use of the intra-aortic balloon pump, enhancing cardiac output, stroke volume, and retrograde aortic diastolic flow. Methods: Twelve hemodynamic parameters were measured, using the BioZ System (CardioDynamics International Corporation, San Diego, Calif) after I hour (n=22) and after 35 hours (n=16) of EECP treatment compared with baseline. The BioZ System noninvasively measures hemodynamic parameters using the thoracic electrical bioimpedance method. Results: One hour of EECP treatment revealed a significant decrease in cardiac output, stroke volume, contractility, afterload, preload, and myocardial energy production, but systolic time ratios and thoracic fluid content were unchanged. However, after 35 hours of therapy, stroke volume (P less than or equal to0.05), index of contractility (P less than or equal to0.05), and thoracic fluid content (P less than or equal to0.01) were decreased. Conclusions: The acute reduction in contractility, preload, and concurrent bradycardia may have favorable hemodynamic effects for patients with angina pectoris. Further studies are needed to elucidate the mechanism of EECP therapy and its efficacy for patients with angina pectoris.