FLUOROSCOPIC DETERMINATION OF LATISSIMUS-DORSI MUSCLE SHORTENING FRACTION AFTER DYNAMIC CARDIOMYOPLASTY

Optimization of the skeletal muscle contraction during cardiac assist is important to achieve maximal cardiac assist and yet avoid overstimu lation that may injure skeletal muscle. Dynamic cardiomyoplasty suffer s from lack of an objective, reproducible, and accurate technique to m easure skeletal muscle shortening fraction after wrap and training of the muscle. A recruitment curve is considered the best way to select t he proper stimulation level to achieve supramaximal contraction withou t overstimulating the muscle. A fluoroscopic technique of determining latissimus dorsi recruitment curve was evaluated in five goats undergo ing dynamic cardiomyoplasty with an anterior cardio-subcutaneous wrap. Two pairs of stainless steel targets (0.5 and 1 cm of diameter) were implanted on each side of the muscle wrap. One pair of sonomicrometer crystals was also implanted. Displacement of the targets was measured under fluoroscopy at five different stimulation levels. Correlation co efficients between targets on the inside surface of the wrap and the s onomicrometer crystals, and targets on the outside surface of the wrap and the sonomicrometer crystals were 0.71 (P < 0.05) and 0.60 (P < 0. 05), respectively. Targets on the inside surface of the wrap were more accurate than targets on the outside surface of the wrap for measurem ent of skeletal muscle shortening fraction and establishment of a recr uitment curve. Adverse effects from the targets were not observed.