Ultrastructural and capillary adaptation of gastrocnemius muscle to occlusive peripheral vascular disease.

The effect of chronic occlusive peripheral vascular disease (PVD) on the histochemistry and capillarity of the gastrocnemius muscle was studied in 129 biopsies taken from 93 subjects. Sixty-three patients underwent biopsy during surgical procedures, and data related to walking distance and ankle systolic pressure. Thirty biopsies taken from normal subjects post mortem served as a control group, and data were analyzed for fiber type distribution, fiber area, fiber type grouping, and fiber capillarity. Fiber type distribution did not alter significantly between the patients with PVD and the control group, but the mean fiber area of the type 1 fiber in male patients with intermittent claudication (IC) was reduced when compared to that in age-matched controls (4608 +/- 1181 mu 2, IC +/- 1 SD; 5795 +/- 1771 mu 2, controls +/- 1 SD) (P less than 0.05). When bilateral biopsies were taken from the gastrocnemii of patients with unilateral occlusions, the type 2 fibers in the diseased leg were significantly smaller than fibers of the control group (2821 +/- 953 mu 2, IC +/- 1 SD; 4318 +/- 1504 mu 2, controls +/- 1 SD) (P less than 0.02). Fiber type grouping, evidence of denervation and reinnervation of muscle, appeared to be more common in patients with more severe limb ischemia. Overall capillary numbers did not appear to alter with degree of ischemia, but fiber shrinkage appeared to compensate for any loss of capillaries in the more ischemic muscle. These data suggest that the limb of the untrained patient with IC does not adapt to ischemia by adjusting its exercise capacity but merely shows evidence of disuse. These adaptations suggest that there may be much to be gained by nonsurgical methods of treating IC.