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PERIPHERAL VASCULAR ULTRASOUND
essential to have an emergency call system close at hand. In the absence of a treadmill it is possible to exercise the patient along the known length of a corridor. Another alternative is to use commercially available foot flexion devices to exercise the calf muscles while the patient sits on the examination table. This reduces cardiac stress. Exercise testing is also a particularly useful screening test, as some patients exhibiting symptoms of claudication may have other disorders producing their symptoms, such as spinal stenosis, sciatica or musculoskeletal prob- lems. In these cases, the post-exercise pressures will be normal. Unfortunately, there is a wide range of exercise protocols used by vascular laboratories (e.g., speed 2–4 km/hour, exercise duration 2–5 min and treadmill incline 10–12%). This can make com- parisons of results among units difficult. However, individual patients’ performance can be measured on sequential visits to monitor their treatment or progress.
SYMPTOMS OF LOWER LIMB ARTERIAL
DISEASE
Intermittent claudication
Atherosclerosis is a major health problem in devel- oped countries where lifestyle factors, such as diet and smoking, can accelerate the progression of the disease. It is estimated that intermittent claudication affects approximately 4.5% of the population aged between 55 to 74 years, and there is evidence that persons with claudication have a significantly higher mortality rate from cardiac disease than non- claudicants (Fowkes et al 1991). Intermittent clau- dication is caused by arterial narrowing in the lower limb arteries, and symptoms may develop over a number of months or years. Claudication is typified by pain and cramping in the muscles of the leg while walking, which usually forces the patient to stop and rest in order to ease the symptoms. The severity of pain experienced and the distance a patient is able to walk can vary from day to day, but, generally, walking briskly or on an incline will produce rapid onset of symptoms. The location of pain (i.e. calf, buttock or thigh) is often associated with the distribution of disease. For instance, aortoil- iac disease often produces thigh, buttock and even- tually calf claudication whereas femoropopliteal
disease is associated with calf pain. There are some- times physical signs of deteriorating blood flow in the lower limb, such as hair loss from the calf and an absence of nail growth. Claudication only occurs during exercise because, at rest, the muscle groups distal to a stenosis or occlusion remain ade- quately perfused with blood. However, during exercise the metabolic demand of the muscles increases rapidly, and the stenosis or occlusion will limit the amount of additional blood flow that can reach the muscles, so causing claudication.
Many patients with intermittent claudication are treated by conservative methods. This includes reduction or elimination of risk factors associated with atherosclerosis, such as smoking. Patients are also advised to undertake a controlled exercise pro- gram to build up the collateral circulation around the diseased vessel, which may ease symptoms over time. If necessary, serial ABPI measurements or exercise tests can be performed to monitor the patient’s progress. Interventional treatment is mainly by angioplasty which involves the dilation of stenoses or occlusions with percutaneous balloon catheters (see Ch. 1). Arterial stents are sometimes used to prevent re-stenosis, although in-stent stenosis is known to occur in a proportion of cases due to the development of intimal hyperplasia (see Fig. 9.21). Sometimes the arterial lesion is so hard, the stent will not fully expand, leaving a residual stenosis. Duplex scanning can be used to detect and monitor in-stent stenosis. Surgical bypass is usually avoided, unless the patient is suffering from severe claudica- tion, as there is a small but potential risk of compli- cations occurring during or after surgery, which in extreme cases could lead to amputation or even death.
Chronic critical lower limb ischemia
Critical lower limb ischemia occurs when blood flow beyond an arterial stenosis or occlusion is so low that the patient experiences pain in the leg at rest because the metabolic requirements of the distal tissues cannot be maintained. This is frequently typi- fied by severe rest pain at night, forcing the patient to sleep in a chair or to hang the leg in a dependent position over the side of the bed. This improves blood flow due to increased hydrostatic pressure. Ulceration and gangrene may also be present