PHYSICAL EXAMINATION

LABORATORY STUDIES

Segmental blood pressure readings show a marked decrease in blood pressure when measured at the calf. Pulse volume readings are also reduced at the calf. The ankle-brachial index is 0.8 (normal: 0.95 to 1.20). Duplex ultrasound imaging shows an increased lumen blood flow velocity in both calves, indicating areas of stenosis. Contrast angiography reveals widespread arterial calcifications in the arteries below the knee.

DIAGNOSIS

Intermittent claudication

COURSE

Angioplasty of the lesions was performed, resulting in improved leg blood flow and restoring the ability to exercise.

PATHOPHYSIOLOGY OF KEY SYMPTOMS

Tissue blood flow is determined by the pressure gradient and the vascular resistance. The pressure gradient remains fairly constant, unless there is an abrupt decrease in arterial pressure. Vascular resistance, however, is regulated by local metabolic control, sympathetic nerves, and circulating vasoactive hormones.

During exercise there has to be an increase in muscle blood flow to provide sufficient oxygen and other nutrients and to remove metabolic wastes. Exercise results in an increase in adenosine triphosphate (ATP) consumption, and replenishing the ATP stores requires increased oxygen delivery to the muscle (Fig. 16-1). Hypoxia is a powerful local vasodilator, and a decrease in vascular resistance results in an increase in blood flow to the exercising muscle. Metabolic wastes also serve as vasodilators, and metabolic control results in the autoregulation of tissue blood flow (Fig. 16-2).

FIGURE 16–1 Effect of increasing rate of metabolism on tissue blood flow.