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Peripheral Arterial Disease in People with Diabetes
 While it has long been recognized that diabetes is a risk factor for the development of peripheral arterial disease (PAD), it was not clear to many doctors and their patients the exact prevalence and the impact on the quality of life which PAD has in people with diabetes. PAD refers to the narrowing and blockages that occur in the lower extremities that limit blood flow and circulation to the legs and feet. The impression has been that people with diabetes are more commonly afflicted with PAD.
In 2003, the American Diabetes Association (ADA) convened a panel of experts to present their knowledge in order to reach a consensus on the issues of PAD in people with diabetes. Several striking conclusions were presented in the consensus statement issued by the ADA and endorsed by VDF.
First, PAD is much more common in people with diabetes than previously thought. Based on several large screening studies, PAD was found to be present in approximately 25% of the subjects, or one in four individuals with diabetes over the age of 50. The development of PAD seems to "incubate" during the stage of pre-Type-2 diabetes, where the blood sugar may still be relatively normal. The metabolic changes in blood fats or lipids, blood pressure rises, and resistance to the healthy effects of the body's own insulin, all may explain why many people with Type 2 already have PAD at the time when they are first diagnosed with diabetes.
The reason that PAD in people with diabetes has gone undetected for so long is that most people have no symptoms. Most do not have intermittent claudication, the gripping pain in the calves or legs with walking that is relieved by rest. If people do have symptoms, they may be subtle initially, such as slow walking speed, or fatigue, or heaviness of the legs. These are often not recognized as being a disease but instead are believed to be changes that occur simply from getting older. Worse yet, research has shown that, unless addressed and treated, these functional changes will continue to deteriorate and can lead to disability.
Diabetes increases the likelihood that PAD will be present without symptoms. As a risk factor, diabetes is unique in that it allows PAD to affect the smaller blood vessels below the knee rather than the usual impact in the larger blood vessels in the thigh or in the pelvis. This makes PAD in the presence of diabetes less likely to cause pain and symptoms. In addition, PAD in diabetes is almost always accompanied by neuropathy, or nerve damage in the lower legs, which may also mask circulation discomfort. Despite the lack of symptoms, people with PAD and diabetes often have significant functional impairment, especially in walking speed and distance. Diabetic patients with both neuropathy and PAD are also at increased risk for developing a non-healing sore on the legs, or even needing an amputation.
PAD has been associated with a high risk of heart attack or stroke, and this is even more so in a person with diabetes and PAD, where it is estimated that about one out of three will have such an event over five years. Fortunately, a lot of this excess risk can be lowered with proper treatments of diabetes, cholesterol, and blood pressure. Blood thinners such as aspirin may be used.
Even though most people have no symptoms, screening for and diagnosing PAD are important. It can identify someone at high risk for heart attack and stroke, and can uncover symptoms and poor function of movement which could lead to disability and, at worst, amputation or death.
The best way to screen for PAD is a measurement of the blood pressure in the ankle. When this blood pressure is compared to that in the arm, an ankle-brachial index (ABI) can be calculated. The blood pressure in the ankle should be about the same as that in the arm. When the ankle pressure is lower than that in the arm, the diagnosis of PAD is made.
The test can be performed in a doctor's office or a hospital laboratory using a blood-pressure cuff and a special microphone called a Doppler. According to current treatment guidelines, an ABI should be performed on anyone with diabetes over 50 years of age.
When someone with diabetes has been found to have PAD, there should be focus on two treatment objectives. The first is strictly addressing the high risk of heart attack and stroke by treating the factors of diabetes, hypertension, cholesterol, and blood clots. The second treatment objective is to improve the symptoms and function of the legs in order to prevent disability and limb loss.
To prevent heart attack and stroke, the ADA recommends that patients "know your ABCs," which are explained as follows.
The goals of treatment are listed below:
- A1c: less than 7%
- Blood Pressure: less than 130/80
- LDL Cholesterol: less than 100 mg/dl
While the blood sugar (A1c measurement above) is important for overall health, the benefits are greater with cholesterol and blood pressure management. Almost every person with diabetes and PAD should be on a "statin" drug with a goal of an LDL cholesterol under 100 mg/dl, and, for some, even less than 70 mg/dl. As for blood-pressure control, more than one medication is often required.
In addition, all patients with diabetes should be taking something to prevent the blood clots that cause heart attacks and strokes, such as a baby aspirin. Some patients with diabetes and PAD may benefit more from a prescription medication called clopidogrel.
For symptoms and poor walking ability from PAD, supervised exercise in a rehabilitation facility or clinic has been shown to be extremely effective treatment. The recommendation is 35 minutes of treadmill walking three times a week initially, and a gradual increase to 50 minutes per session. A prescription medication, cilostazol, may also increase walking distance. In more severe cases, invasive procedures such as balloon angioplasty, stenting, or bypass surgery may be required.
If you are over 50 years of age and have diabetes, ask your provider about checking for PAD. There are many things that can be done to save limbs and lives.
About the Author: Peter Sheehan, MD serves as a senior faculty member at the Mount Sinai School of Medicine and has a particular interest in peripheral neuropathy, foot ulcerations, charcot osteoarthropathy, and peripheral arterial disease.
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