Relationship between gastrocnemius capillary supply and walking capacity in Peripheral Arterial Disease

Purpose Patients with Peripheral Arterial Disease (PAD) have a reduced exercise tolerance, the exact causes of which are poorly understood. We aimed to investigate the capillary supply of the medial gastrocnemius muscle and walking capacity in a group of PAD patients (n = 16, age: 63y) and healthy control subjects (n = 13, age: 62 years). Methodology Exercise capacities were measured with an incremental treadmill-walking test. A resting muscle sample was taken from the medial gastrocnemius of the most diseased limb in the PAD patients and a randomly chosen limb in the CON subjects, and it was analysed histochemically for fibre type, fibre area, capillary to fibre ratio and capillary contacts per fibre. Results Exercise performance was 50–60% lower in the PAD patients compared with CON. PAD patients had a relatively greater proportion of type IIA (PAD:27%; CON:16%) and lower proportion of type I (PAD: 49%; CON:62%) muscle fibres, fewer capillaries per fibre (PAD:1.63; CON:2.12), and tended to have smaller fibre areas (∼10%). In PAD patients only, the area of all three fibre types and the capillary contacts with type I and IIA fibres were positively correlated (P less than 0.05) with treadmill walking performance. Conclusion These data suggest that a low muscle capillary supply may contribute to the exercise intolerance of PAD patients