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

Background: Enhanced external counterpulsation (EECP) is an effective nonin vasive treatment for patients with angina pectoris. However, the hemodynami c effects of EECP are still unknown and have been theorized to simulate the clinical use of the intra-aortic balloon pump, enhancing cardiac output, s troke 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 tho racic electrical bioimpedance method. Results: One hour of EECP treatment revealed a significant decrease in card iac output, stroke volume, contractility, afterload, preload, and myocardia l energy production, but systolic time ratios and thoracic fluid content we re unchanged. However, after 35 hours of therapy, stroke volume (P less tha n or equal to0.05), index of contractility (P less than or equal to0.05), a nd 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 th erapy and its efficacy for patients with angina pectoris.