The Double Whammy: When Peripheral Artery Disease Complicates Peripheral Neuropathy
When it comes to your feet, it’s important to know where you stand. Foot problems are the most common reason for diabetes-related hospitalizations, and people with diabetes are up to fifteen times more likely to have a lower limb amputation than those without diabetes.
The problem is caused by two mechanisms: macrovascular (affecting the big arteries) problems and microvascular (affecting the small arteries and capillaries) problems. Microvascular problems, created by high circulating levels of glucose over long periods, cause diabetic peripheral neuropathy (DPN). DPN is a nerve condition that may result in either prickling pain or the inability to feel sensation in your feet and legs. Without the ability to feel pain, you may end up overlooking an injury to your foot. And if you also have peripheral artery disease (PAD), it’s likely that any such injury won’t heal well.
When you have PAD, the big arteries supplying your legs and feet are narrowed, weakened, and hardened. It’s the same mechanism that causes atherosclerosis in the cardiac arteries. The result is called ischemia, which is when the body part supplied by the blocked artery does not get enough oxygen-carrying blood. This macrovascular problem results in poor circulation that impairs healing: Without sufficient oxygen, even a minor injury can develop into a serious infection.
The lack of oxygen can trigger various symptoms, including pain in the calves, thighs, or hips when walking (called “intermittent claudication” which means “occasional limping”). It can also cause cold feet and bluish discoloration, absence of hair on the legs, and even gangrene, which is when the affected body part begins to die from lack of oxygen. When blood vessels in the legs are completely blocked, leg pain at night is common, causing the sufferer to hang his or her feet down to ease the ache. Pulses in the leg are decreased or absent, indicating a lack of arterial blood flow.
About half of people with PAD either do not have symptoms or believe that their symptoms are simply part of normal aging. To discover PAD in such a person, one widely-used test is the Ankle/Brachial Index (ABI), a measure that compares the blood pressure in the arm (brachial) with the blood pressure in the legs. In a person with healthy blood vessels, the pressure is higher in the legs than in the arms. In a person with PAD, it’s the opposite.
People with PAD can be treated with lifestyle changes, medications or both. Lifestyle changes that lower risk include stopping smoking, controlling blood sugar and blood pressure, being physically active, and eating a low-saturated-fat, low-cholesterol diet. Medications include those to help increase walking distance (cilostazol and pentoxifylline); anti-platelet agents; and cholesterol-lowering agents (statins).
If these measures don’t work, angioplasty may be necessary. Angioplasty is a non-surgical procedure that can be used to widen narrowed or blocked peripheral arteries. A thin tube called a catheter, with a balloon on its tip, is pushed into the narrowed artery segment and then inflated. After it widens the artery, the balloon is deflated and the catheter is withdrawn. Often a stent (a cylindrical wire-mesh tube) is also pushed into the artery, where it expands and locks open to keep blood flowing. Sometimes the stent is coated with slow-release drugs that inhibit re-growth of the blockage; if so, it’s called a drug-eluting stent.
Another procedure, called excimer laser ablation, employs the same type of laser used in LASIK eye surgery. A small fiber optic catheter is threaded into the artery, where it sends short precise bursts of “cool” ultraviolet energy into the top of the plaque blockage. Layer by layer, the laser energy disintegrates (ablates) the plaque into tiny particles that are easily absorbed into the blood stream. One treatment option is Spectranetics’ laser ablation system. The procedure is generally covered by insurance.
If the narrowing involves a long section of an artery, bypass surgery can be used. A vein from another part of the body, or a synthetic blood vessel, is attached above and below the blocked area to detour blood around the blockage.
Sources: Medical Journal of Australia
American Diabetes Association