Muscle fiber characteristics in patients with peripheral arterial disease

Purpose: There have been conflicting reports of muscle Fiber type changes i n patients with peripheral arterial disease (PAD). The purpose of this stud y was to examine the myosin heavy chain (MHC) expression as well as histoch emical changes in the gastrocnemius muscle in patients with symptomatic PAD . Methods: Needle biopsy specimens were obtained from the medial gastrocnem ius of 14 subjects with PAD (mean age (+/- SD), 69.7 +/- 4.8 yr) and eight activity-matched control subjects (mean age, 65.1 +/- 6.6 yr). Ankle-brachi al index was assessed using Doppler ultrasound to determine the hemodynamic status of the patients, and maximal walking performance was determined dur ing a graded treadmill test. Expression of MHC isoforms was determined by S DS-PAGE. Results: The proportion of MHC I was significantly smaller in PAD than in the controls (45.6 +/- 9.1% vs 58.8 +/- 15.0%). The proportion of M HC IIx was also larger in the subjects with PAD compared with the controls (22.9 +/- 9.1% vs 16.0 +/- 11.3%). In addition, there was a significant dec rease in the cross-sectional area of the type I and type IIA fibers in the subjects with PAD as well as enhanced capillary density. Conclusion: This s tudy showed a significant modification in the expression of MHC isoforms an d muscle fiber type in the gastroenemius in patients with symptomatic PAD. These results suggest that muscle ischemia resulting from PAD is an importa nt factor in causing the adaptations in the contractile apparatus of the mu scle.