Factors affecting the integrity of latissimus dorsi muscle grafts: implications for cardiac assistance from skeletal muscle.
BACKGROUND: Severe latissimus dorsi muscle damage may compromise cardiomyoplasty performance. We analyzed factors underlying the damage produced in 20 sheep latissimus dorsi muscles by isolating the influences of electrical stimulation, mobilization (with some loss of vascular supply), loss of normal resting tension, or a combination of these. METHODS: In group I (n = 3), the muscle was mobilized except for its neurovascular pedicle and reattached at normal resting length. In group II (n = 3), the muscle was mobilized and reattached at about 80% of resting length. Groups III (n = 6) and IV (n = 4) were as groups I and II except that continuous indirect stimulation at 2 Hz was added after 2 weeks. In group V (n = 4), the undisturbed muscle received stimulation alone. After 10 to 12 weeks, muscle samples were taken for morphometric analysis. RESULTS: Loss of resting muscle tension appeared to be the single most damaging intervention, though mobilization and stimulation had further deleterious effects. The worst damage was seen when all three factors were combined, when 60% of the muscle cross section was occupied by connective tissue and fat. The changes were significantly more severe in the distal than in the proximal part of the muscle, implicating ischemia as a contributory factor. CONCLUSIONS: Fiber damage reduces the effectiveness of muscle grafts used for cardiac assistance and merits further systematic investigation.