CHANGES IN SKELETAL-MUSCLE MORPHOLOGY AND BIOCHEMISTRY AFTER CARDIAC TRANSPLANTATION

Skeletal muscle biopsies (vastus lateralis) were performed in 12 patie nts (mean age 47 +/- 11 years) before and at 3 and 12 months after car diac transplantation. Fiber type analysis revealed a predominance of t ype II fibers before cardiac transplantation (66 +/- 10%); the ratio d id not change after transplantation. Fiber cross-sectional area increa sed by 35% to 39% in all fiber types by 12 months after cardiac transp lantation. Fiber cross-sectional area, however, remained below the rep orted normal values. The number of capillaries surrounding each fiber did not change after cardiac transplantation, Skeletal muscle enzyme a ctivity of phosphofructokinase, citrate synthase, and beta-hydroxyacyl coenzyme A dehydrogenase increased by 26%, 47%, and 63%, respectively , after cardiac transplantation (p < 0.05). Peak oxygen uptake also in creased significantly after cardiac transplantation (19.5 +/- 8.1 ml/k g/min at 12 months vs 9.8 +/- 1.4 ml/kg/min before transplant, p < 0.0 1); however, uptake remained 40% below that of predicted. Thus, signif icant improvement in skeletal muscle morphology and biochemistry occur s in the first year after cardiac transplantation in association with improved exercise capacity. Recovery, however, may be incomplete, whic h could explain residual impairment of exercise capacity in these pati ents. (C) 1997 by Excerpta Medica, Inc.