Numerical simulation of enhanced external counterpulsation.

Enhanced external counterpulsation (EECP) is a noninvasive, counterpulsative method to provide temporary aid to the failing heart by sequentially inflating cuffs on the lower extremity out-of-phase with the left ventricle. Optimization of the method necessitates consideration of the hemodynamics created by EECP and the mode of action providing patient benefit. A computational model based on the governing one-dimensional equations is developed that simulates cardiovascular hemodynamics during EECP. The model includes a 30-element arterial system including the left ventricle, bifurcations, and peripheral arterial vessels. Effects of vessel collapse as external pressure is applied, arterial refilling on pressure release, changes in aortic pressure, and shear stress generated in the arteries are each investigated. Device parameters are systematically varied to determine their effect on system performance. Results show the potential for significant collapse and shear augmentation throughout the arteries of the lower extremity. Performance is strongly influenced by the mean level of external pressurization and the timing of cuff inflation, but less so by the relative timing and pressure differences between cuff segments.