CARDIOMYOPLASTY - DEGENERATION OF THE ASSISTING SKELETAL-MUSCLE

This study determined effects of surgical dissection and chronic stimu lation on degeneration of the latissimus dorsi muscle (LDM), the muscl e used for contractile assistance in cardiomyoplasty. LDMs from 10 goa ts were allocated into four groups: N-LDM (normal), D-LDM (dissected m uscle and collateral vessels ligated, muscle remained in original anat omic location), S-LDM (electrically stimulated for 62-75 days), and DS -LDM (dissected and stimulated). S-LDM had nearly a complete transform ation to type I fibers throughout the length of the muscle. Both group s of dissected muscles (D-LDM and DS-LDM) showed lesser transformation and significant damage. Type I myosin heavy chain and citrate synthas e activity were less in the distal compared with the proximal LDM. Mor phology of the N-LDM and S-LDM was normal, whereas dramatic morphologi cal abnormalities were observed in the D-LDM and DS-LDM, including lip id-containing ghostlike fibers, atrophied and hypertrophied fibers wit hin the same fascicle. In conclusion, muscle degeneration associated w ith the cardiomyoplasty procedure was caused by surgical dissection, w hich was exacerbated by chronic stimulation but was not caused by stim ulation alone.