Improved Exercise Tolerance After Losartan and Enalapril in Heart Failure: Correlation With Changes in Skeletal Muscle Myosin Heavy Chain Composition

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In congestive heart failure, fatigue-resistant, oxidative, slow type I fibers are decreased in leg skeletal muscle, contributing to exercise capacity (EC) limitation. The mechanisms by which ACE inhibitors and AII antagonists improve EC is still unclear. We tested the hypothesis that improvement in EC is related to changes in skeletal muscle composition toward type I fibers.


Six months' treatment with L and with E produces an improvement in EC of similar magnitude. These changes are accompanied by a reshift of MHCs of leg skeletal muscle toward the slow, more fatigue-resistant isoforms. Magnitude of MHC1 changes correlates with the net peak VO2 gain, which suggests that improved EC may be caused by favorable biochemical changes occurring in the skeletal muscle. (Circulation. 1998;98:1742-1749.)

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