AN ENGINEERING MODEL OF DYNAMIC CARDIOMYOPLASTY - I

Dynamic cardiomyoplasty (DCM) is an emerging surgical procedure for he art failure in which the patient's latissimus dorsi (LD) muscle is wra pped around the heart and stimulated to contract in synchrony with the heartbeat as a cardiac assist measure. A 6 week training protocol of progressive electrical stimulation renders the normally fatiguable ske letal muscle fatigue-resistant and suitable for chronic stimulation. T o date, over 500 procedures have been performed in worldwide clinical trials. Investigators typically report symptomatic improvement and mod est hemodynamic improvement in patients. Controversy exists regarding the exact mechanism of DCM. To test the hypothesis that DCM augments c ardiac stroke volume through improvement in systolic function, we form ulated an engineering model of dynamic cardiomyoplasty to predict stro ke volume. The heart and the LD were modeled as nested (series) elasta nce chambers, and the vasculature was represented by a two-element Win dkessel model. Using five healthy goats, we verified model predictions of stroke volume for both stimulator ON beats (y=1.00x-0.08, r=0.87, p <0.0001) and OFF beats (y=1.01x+1.06, r=0.91, p <0.0001), where x an d y are the measured and predicted stroke volumes, respectively. The m odel confirms that using untrained latissimus dorsi applied to the nor mal myocardium produces only moderate increases in stroke volume and s uggests that future research should focus on increasing LD strength af ter training. (C) 1998 Biomedical Engineering Society.