Force and histochemical changes in rabbit pectoral muscle induced by chronic electrical stimulation for use in...

Before the application of skeletal muscle in a cardiac-assist device, a preconditioning procedure is required in order to overcome the easy fatigability of this muscle. We evaluated the effect of preconditioning muscles while keeping their collateral blood supply. In 15 male rabbits, a skeletal muscle ventricle (SMV) was constructed from silicone and pectoralis major muscle with minimal dissection. In six rabbits, the muscle was electrically preconditioned. The pressure generated by the SMV was measured under various conditions. Histochemical fiber grouping was performed using myosin ATPase staining. The pressure rose with preconditioning despite an increase in slow-twitch fibers. The cross-sectional area of both slow-twitch and fast-twitch fibers increased significantly. The rise in pressure is attributable to muscle hypertrophy. The use of muscles with minimal dissection may avoid or shorten the vascular delay because of a well maintained blood supply and nearly isometric preconditioning.