By William Kirk, MD
Unfortunately, as the title of this article suggests, diabetes and lower extremity peripheral vascular disease go hand-in-hand. Studies show that lower extremity ischemia, stroke or death from ischemic heart disease occurs in more than 60 percent of diabetic patients. In a busy San Antonio vascular surgery practice, a majority of patients will have diabetes mellitus that is typically manifested by lower extremity vascular disease with threatened
limb loss or renal insufficiency necessitating dialysis access.
The number of patients with diabetes in the United States is estimated to be 20 million, projected to double in 20 years. In this century, diabetes will be the most common chronic medical condition affecting Americans. Approxi-mately 90 percent of patients affected have diabetes mellitus (DM) type II, which is seen in genetically susceptible individuals in association with the metabolic syndrome of central obesity, hypertension, hyperlipidemia and glucose intolerance. Its underlying mechanism is insulin resistance. In contrast, DM type I is secondary to pancreatic islet cell destruction caused, again, by genetic susceptibility, but likely prompted by a viral infection.
Diabetic patients often develop atheroschlerosis which results from prolonged elevated glucose levels. This occurs at the microvascular level causing pathology, for example, in the kidneys, eyes and nerves secondary to thickened basement membranes. Similarly, it causes pathology at the macrovascular level affecting the large named arteries with the development of vessel lumen obstructing atherosclerotic plaques. Of course, there are often additional risk factors for atherosclerosis such as hypertension, hyperlipidemia and smoking. Other risk factors for peripheral arterial disease include increased fibrinogen levels and hyperhomocysteinemia.
In studies evaluating the reduction of the major risks for atherosclerosis, only smoking cessation has been shown to im-prove lower extremity vascular symptoms (This study was not conducted solely on diabetic patients). While elevated glucose levels are known to contribute to atherosclerotic plaque forma-tion, subsequent “tight” glucose control has failed to demonstrate a reduction in cardiovascular risks, leading me to doubt its effectiveness in reducing peripheral vascular risk, as well.
Ultimately, the key to management of DM (type II) is prevention initiated early in life through healthy lifestyle, proper diet and exercise, and of course, never reaching for a cigarette.
Atherosclerotic plaque and resulting lesions may be present for quite some time in the diabetic patient before symptoms such as claudication, rest pain or tissue loss occurs. It is typically not until then, unfortunately, that the vascular surgeon is called upon for evaluation. The location of lower extremity atherosclerotic lesions in diabetics is unique. The typical non-diabetic patient with symptomatic peripheral vascular disease will have atherosclerotic plaques above the knee with sparing of the important collateral profunda femoral artery. In diabetic patients, however, the arterial territory most likely to be affected is below the knee or infrageniculate as well as affecting the profunda femoris.
Surprisingly, the foot arteries are frequently spared. Surgical intervention is typically reserved for patients with tissue loss or gangrene. Because the arterial beds of diabetics are usually distal in the lower extremities with patency of the arteries of the foot, a bypass is often possible. Other invasive procedures that may be beneficial include angioplasty, stenting and atherectomy devices.
In my practice, it has concerned me greatly that few medical therapies have demonstrated benefit to the diabetic patient. Aspirin and clopidrogel, which are both antiplatelet agents that act via different mechanisms, have shown no benefit in ameliorating claudication-type symptoms. Aspirin does, however, apparently reduce the risk of peripheral vascular surgery.
The statin agents which lower LDL cholesterol and also reduce plaque inflammation, likely stabilizing these plaques, have been shown to be of great benefit in the coronary circulation. However, these agents have not been fully evaluated for lower extremity atherosclerosis in diabetics or non-diabetics. In fact, LDL cholesterol may be only minimally associated with lower extremity peripheral arterial disease, if at all. A study which included a significant percentage of diabetics has shown that Cilostazol, which is a phosphodiesterase III inhibitor with antiplatelet, antithrombotic and vasodilatory effects, improves walking performance in vascular claudicants.
In light of the enormously increasing diabetic population, as well as the increasing amount of money spent to fight this disease, political leaders and the general public need to be aware of and interested in prevention of this devastating health issue.
Dr. Kirk is a board certified vascular surgeon, practicing with Peripheral Vascular Associates since 1993. His practice primarily covers the Northeast Baptist and Northeast Methodist hospitals.
