The vast majority of peripheral arterial disease is caused by arteriosclerosis obliterans (ASO), a progressive occlusive disease of the arteries. ASO is believed to begin by the formation of a fatty streak in the artery called atherosclerosis. These fatty streaks localize in the wall of the blood vessel and harden over time forming ASO. Complete occlusion of the artery results in disruption of blood flow to the target organ. Males are more predisposed to ASO and are subsequently more inclined to develop wound healing problems associated with PAD. Other factors that contribute to non-healing wounds include mechanical stress, lipid disorders and high blood pressure. Tobacco use, whether smoking, snuff or chew is a significant contributing factor. Circulating levels of nicotine make the blood more acidic. As a result, nicotine makes the artery wall much more permeable to atherosclerotic plaque, increasing the likelihood of ASO.

Arterial foot and leg ulcers occur as a result of advanced peripheral arterial disease. Occlusion of the arteries of the leg and foot impair healing resulting in non-healing wounds and chronic ulcerations. Wagner described the classification used to describe arterial ulcers and wounds used most commonly today.

Wagner Grade 0 - Irritation of the skin with no break in the skin.

Wagner Grade 1 - Superficial wound with no infection. Skin is intact but erythematous.

Wagner Grade 2 - Partial to full thickness erosion of the skin. Infection possible. No deep tissue or bone involvement.

Wagner Grade 3 - Full thickness, deep tissue involvement. Wound is infected with probably bone infection.

Wagner Grade 4 - Deep, extensive infection with gangrene.

Diagnosis of peripheral arterial disease begins with a history and physical exam. Painful cramps at night, called nocturnal claudication, are one symptom of compromised arterial circulation. Another finding of PAD would include an inability to walk distances due to pain or heaviness in the legs. This symptom is called intermittent claudication. Patients with advanced peripheral arterial disease find it difficult to raise their feet to sit in a recliner chair or lay in bed. With compromised arterial flow, blood has a difficult time ascending the leg. Therefore, many patients with PAD will sleep with their foot hanging off the edge of the bed.

The physical exam in cases of peripheral arterial disease starts with the palpation of pedal pulses. Patients with advanced PAD will present with an absence of both pedal pulses.  Additional physical exam findings in patients with PAD include loss of hair growth and thin, shiny skin. Delayed capillary refill time (CFT) is suggestive of small artery disease. Normal CFT is less than 3 seconds. CFT greater than 5 seconds is considered suggestive of PAD.

Vascular testing for PAD is initially performed by office based Doppler exams. Doppler exams are helpful in two respects.  Doppler exams used for PAD can both quantify and qualify peripheral arterial flow.  To quantify peripheral arterial flow, lower extremity measurements are compared to blood pressure readings of the arm.  This comparison is called an ankle brachial index or ABI.  ABI testing is crucial to determining the ability of a foot wound to heal.  Doppler exams can also be used to qualify vascular testing.  The waveform generated during the Doppler exam can describe the degree of elasticity vs calcification (hardening) of the artery. If ABI testing shows a significant decrease in arterial flow, hospital based x-ray studies using dye, called an arteriogram, are used to determine the exact location of arterial blockage of the leg.

Treatment of Peripheral Arterial Disease and Ischemic Ulcers

Treatment of PAD consists of a combination of medical and surgical care. Patients who are smokers will benefit greatly from smoking cessation. Statin therapy to decrease lipid levels is also imperative.  Blood pressure must be carefully regulated to prevent hardening of arteries.  Increased exercise may contribute to collateral circulation and may improve blood flow to ischemic limbs.

Several oral medications are used to treat peripheral arterial disease. Calcium channel blockers (Verapamil, Calan), although primarily used as antihypertensive agents, may be used to increase small vessel peripheral blood flow. Trental (pentoxifylline) is an oral medication that is used to treat PAD decreasing the viscosity of the blood. Trental coats the red blood cell so that it becomes slippery and able to travel through occluded vessels. Pletal (cilostazol) is another oral medication used to treat PAD. Pletal inhibits cellular phosphodiesterase resulting in dilation of arterial vascular beds. Recent studies have shown a significant reduction in intermittent claudication symptoms with the use of Pletal.

Arterial bypass surgery, developed during the 1970's, is still a common surgical method used today but may only be used on the medium to large vessels of the leg. Until recently, revascularization was limited to bypass grafting with harvested grafts or synthetic grafts. During the past twenty years there have been significant advances in endovascular techniques used to revascularize the leg and foot.  Endovascular techniques focus on clearing the blockage of the leg by using balloons to compress plaque or devices to ream plaque, re-opening occluded vessels.  There is an ongoing controversy among both physicians who perform these procedures and insurance companies who pay for these services, as to which procedure (open vascular bypass or endovascular angioplasty) has the best long term success rate.  Although the debate is ongoing, there is a clear consensus that endovascular procedures are indicated for patients who are high risk patients due to co-morbidities such as advanced age, diabetes or advanced heart disease.

Wound care is an important aspect of PAD treatment. Treatment of wounds with serial debridement of devitalized tissue is imperative.  Treatment of infection any be necessary with antibiotics, whether topical, oral or IV. Protection (off-loading) of the wound is essential. Many devices have been invented for this purpose to act as a cradle or pad for the wound. Many physicians use adjunctive wound therapies such as topical enzymes for wound debridement or wound growth factors to enhance wound healing.

Unfortunately, amputation is still all too common for advanced cases of peripheral arterial disease. The level of amputation is dictated by vascular testing that includes Doppler exam and/or aortic arteriogram.  The post-operative success of amputation depends to a great extent upon the patient's functional capacity going into their surgery.  Patients greater that 70 y/o have a three fold higher risk of death from amputation surgery when compared to a patient 20 years younger.  Older patients are also less likely to use prosthetics post amputation and are 4 times more inclined to loose their independent living status post amputation when compared to similar patients age 50 y/o or less.  These outcome statistics remain the same regardless of surgical method used (open vs endovascular). 

Two additional factors may negatively influence the outcomes of amputations performed for PAD.  These two factors are diabetes and end stage renal disease.  Patients with diabetes or end stage renal disease have significantly poorer long term success rates with revascularization, regardless of method of revascularization.  In patients with diabetes, the risk of PAD increases with age.  Patients with diabetes who are over the age of 40 y/o are 2-3 times more likely to have PAD.  The lifetime risk for diabetics patients for amputation is 15-25%.  Diabetic patient tend to have more distal symptoms of PAD with occlusion distal to the knee and are less likely to benefit from revascularization compared to PAD patient who are not diabetics.