Peripheral Arterial Disease

Peripheral artery disease (PAD) is a condition of the blood vessels that leads to narrowing and hardening of the arteries that supply the legs and feet. This results in inadequate blood supply to the extremity.

PAD is caused by cholesterol plaque, which accumulates in the inner lining of the artery and causes the artery channel to narrow, thus impeding blood flow. In severe cases, the plaque can completely block and occlude the artery.

PAD usually develops after the age of 50, and is more common in men than in women. It is closely associated with coronary artery disease and is frequently present, to some degree, in patients who have coronary disease. Other risk factors for PAD include smoking, high cholesterol, diabetes, and hypertension.

When arteries become narrowed with PAD, the blood flow to the legs and feet diminishes. This leads to “oxygen starvation” of the muscles, which causes symptoms of pain in the thigh or calf. The pain typically occurs on exertion, such as during walking—especially walking up an incline—and resolves after a few minutes of rest. Diminished blood flow to the skin can cause skin breakdown and development of ulcers. These ulcers typically occur on the tips of the toes, where the oxygen levels are lowest. In severe cases, the oxygen deficiency can lead to tissue death, a process known as gangrene.

PAD is a serious condition, not simply because of its effects on the circulation of the legs, but also because it implies the presence of atherosclerosis in other vascular beds. A patient with PAD has a risk of future heart attack that is equal to a patient with known coronary artery disease. A patient with PAD also has an increased risk of cerebrovascular arteriosclerosis and stroke.

Diagnosing PAD

PAD can usually be diagnosed with a thorough history and physical exam performed by a vascular specialist. In addition, there are several tests that are helpful in diagnosing PAD and in assessing its severity. The ankle-brachial index (ABI) is the simplest of the tests. It involves measuring the blood pressure in the arms to that at the ankles. A normal ratio of the ankle pressure to the arm pressure, the “ankle-brachial index,” is 1.0. An ABI < 0.9 indicates mild PAD, an ABI < 0.7 indicates moderate PAD, and an ABI < 0.5 indicates severe PAD.

The mainstay PAD testing is the lower extremity arterial ultrasound. This test is painless, does not require any preparation, takes about an hour, is relatively inexpensive, and is widely available. It is performed in a dedicated vascular ultrasound lab. The test involves imaging the arteries of the leg with an ultrasound probe, and assessing the dynamics of blood flow through the legs. The arterial ultrasound provides a thorough and very precise assessment of the health of the peripheral arterial vasculature, and the adequacy of blood flow through the legs.

A slightly more invasive imaging test is the CT angiogram or MR angiogram. This involves imaging the arteries of the legs using a CT scan or MRI scan. These tests require an IV and administration of IV iodine contrast (CT) or gadolinium contrast (MRI). Some patients with kidney problems may not be able to tolerate either of these types of contrast.

Lastly, if the above testing is equivocal, then formal angiography can be performed. This involves direct imaging of the leg arteries by inserting a catheter into the femoral artery and imaging with iodine contrast using x-ray visualization.

Treating PAD

The first step in treating PAD is risk factor modification. This consists of smoking cessation, low-fat diet, exercise, and control of diabetes. An exercise/walking program is an important component of this treatment, as exercise stimulates the development of new arterial vessels to supply blood to the oxygen-deficient muscle. The second line of therapy is the initiation of medications to stabilize the disease. These include aspirin and cholesterol-lowering medication. Lastly, percutaneous or surgical interventional procedures are available to open the diseased arteries and restore blood flow to the foot.

Surgical intervention involves open repair or bypass of the diseased artery, under general anesthesia. Percutaneous intervention involves repair of the artery via a small (2mm) puncture made in the femoral artery at the groin. Through this puncture, catheters are introduced and positioned to the area of disease, under x-ray imaging. The artery is then repaired by performing a balloon angioplasty and stent procedure. Sometimes, if the artery contains extensive clot in addition to cholesterol plaque, powerful clot-dissolving medicine is infused through the catheter to dissipate the clot and open the artery. The percutaneous intervention is done in a hospital angiography lab, but in most cases, does not require overnight hospitalization.