Distribution of muscle changes in experimental ischemic myopathy.

The distribution of ischemic changes was examined in the medial gastrocnemius muscle of the cat, following transient simultaneous clamping of the aorta and femoral artery. Initial changes occurred in the middle portion of the muscle, in the areas corresponding to watershed zones of the primary arteries of the muscle. The superficial layers of the muscle, the regions close to the main stem of the primary arteries, and the entire distal portion of the muscle were the most resistant to ischemic damage. These studies demonstrate that in the feline medial gastrocnemius muscle, the vascular pattern is the primary factor in determining the distribution of ischemic changes. The role of differential muscle fiber vulnerability is only secondary.