Transforming skeletal muscle for myocardial assist: a feasibility study.

Canine experiments were undertaken to determine the feasibility of transforming skeletal muscle for myocardial assistance. Initially, a rectus-muscle pedicle flap was used to power a ventricular assist conduit. A specially designed "pulse-train" stimulator produced skeletal muscle contractions capable of augmenting myocardial function. Statistically significant increases in either systolic or diastolic pressures were achieved by appropriate synchronization and signal delays of the stimulator. Then, the left rectus muscle was conditioned by stimulating it at low frequencies (2 to 10 Hz) for 6 to 12 weeks. The degree of transformation from type II (fast) to type I (slow) fibres was examined and the resultant tolerance to fatigue studied. Preliminary data show that a greater proportion of type I fibres is associated with increased resistance to fatigue. Such transformed skeletal muscle should therefore be more suited to power the cardiac assist devices.