Dr. David B. Raynor, Best Foot Forward, 09/18/12

Peripheral arterial disease (PAD) affects millions of Americans and can have devastating effects: cramping; pain; difficulty walking; cardiac, carotid artery, brain, kidney and wound healing issues are all ailments that may be attributed to PAD.

PAD is the slowing of circulation in the peripheral arterial system away from the heart. Buildup of plaque in a single area of turbulence or damage in an artery, arteriole or capillary may occur resulting in the diminished flow of oxygen-rich blood to the tissue downstream of the blockage. This compromise can lead to symptoms and even death or necrosis of the tissue undersupplied with needed blood.

A gradual narrowing of the diameter of the blood vessel along its course from the heart can also produce the same effects and symptoms. Injury can produce a thrombus (a local clot) or embolus (a thrombus that breaks off and is lodged in a smaller, downstream location), causing a reduction or arrest in blood flow.

Plaque, buildup of cholesterol, fat, proteins, blood cells and calcium can lead to stenosis or the narrowing of the diameter of a vessel, thereby reducing flow in a single area. Or it can also break off and lodge in smaller areas.

Diabetes, hypercholesterolemia and smoking tobacco are some of the causes of diffuse vascular disease. Here, a gradual narrowing of the vessels occurs the further the vessel travels from the heart, producing symptoms rather than a complete, isolated blockage in one arterial segment.

Claudication is a phenomenon in which cramping or pain is produced in muscles when blood flow is inadequate to keep up with the metabolic demands of the activity. Claudication in the feet and legs is a common complaint of those who have PAD. Rest pain or pain in the legs and feet is another common complaint of those with PAD. Ulcers, difficulty healing, non-healing wounds, necrosis or gangrene are often late complications of PAD.

Complications of PAD are very difficult to overcome when the disease gets a large head start. “Catching up” to infection, ulceration and gangrene complications after PAD is established as the culprit can be difficult, frustrating, painful and expensive in many cases.
Early detection is tremendously important in the prevention and treatment of vascular complications from PAD. Lifestyle modification, medication, therapy and surgery for PAD detected early greatly improve the chances of long-term quality of life.

Screening for PAD can be performed by feeling pulses, listening for “turbulence” in arteries, or observing suspicious changes in skin appearance. Testing for PAD ranges from non-invasive to invasive.

Non-invasive testing generally produces results in numbers or ratios. The number or ratio produced can have a predictive value in diagnosing PAD or in determining whether there is enough circulation to heal a wound.

A PVR/ABI uses Doppler technology and blood pressure cuffs to assess the circulation of the lower extremity compare to the upper extremity. It is more sensitive than feeling a pulse and is a good, safe screening test for PAD, but has limitations especially in the face of atherosclerosis or diabetes. A PVR/ABI test result of less than 0.60 is the accepted “cut-off” for wound healing.

In other words, if one has a toe wound or ulcer and the test is scored 0.51 then, all indications are there is not enough blood flow to the area to heal. More testing and surgery is likely necessary in this case.

TBI is a similar test, but performed on the toe and is thought to give a more accurate assessment on the circulation status of the foot for foot and toe ulcers. The test has limitations due to the difficulty in applying the apparatus in many cases. Transcutaneous oxygen pressure (TcPO2) is a test used to quantify the oxygen perfusion in the skin using electrodes, but again has some limitations in accuracy.

Skin perfusion pressure (SPP) is another relatively new non-invasive test to evaluate for the presence and severity of PAD. SPP testing uses non-invasive laser technology and pressure cuffs to assess the perfusion of blood into the tissues of the extremity. This testing seems to have distinct advantages over other forms of non-invasive testing with regards to sensitivity, especially in diabetes and atherosclerosis. SPP should be a consideration in assessing PAD, but it is relatively new and not always readily available.

Invasive studies for PAD include arteriogram using radiopaque dye; CT angiogram, which is similar; and MRA, which use mainly gadolinium contrast agents. These studies are much more sensitive, but are invasive, more expensive, and have their own potential risks.

David B. Raynor, DPM, is a podiatrist in Inverness and can be reached at 352-726-3668 with questions or suggestions for future columns.