FACTORS AFFECTING THE INTEGRITY OF LATISSIMUS-DORSI MUSCLE GRAFTS - IMPLICATIONS FOR CARDIAC ASSISTANCE FROM SKELETAL-MUSCLE

Background: Severe latissimus dorsi muscle damage may compromise cardi omyoplasty performance. We analyzed factors underlying the damage prod uced in 20 sheep latissimus dorsi muscles by isolating the influences of electrical stimulation, mobilization (with some loss of vascular su pply), loss of normal resting tension, or a combination of these. Meth ods: In group I (n = 3), the muscle was mobilized except for its neuro vascular pedicle and reattached at normal resting length. In group II (n = 3), the muscle was mobilized and reattached at about 80% of resti ng length. Groups III (n = 6) and IV (n = 4) were as groups I and II e xcept that continuous indirect stimulation at 2 Hz was added after 2 w eeks. In group V (n = 4), the undisturbed muscle received stimulation alone. After 10 to 12 weeks, muscle samples were taken for morphometri c analysis. Results: Loss of resting muscle tension appeared to be the sngle most damaging intervention, though mobilization and stimulation had further deleterious effects. The worst damage was seen when all t hree factors were combined, when 60% of the muscle crosssection was oc cupied by connective tissue and fat. The changes were significantly mo re severe in the distal than in the proximal part of the muscle, impli cating ischemia as a contributory factor. Conclusions: Fiber damage re duces the effectiveness of muscle grafts used for cardiac assistance a nd merits further systematic investigation.