Diabetes and Vascular Disease

March 15, 2001

Overview

Vascular disease is a relatively common complication of diabetes. Often referred to as “hardening of the arteries” by the lay public, atherosclerosis is the medical term that describes the development of deposits on the inside of arteries. These deposits consist of cholesterol, scar tissue, and calcium that gradually progress over months to years ultimately leading to blockage of the artery. Symptoms develop when the blockage becomes severe. For example, severe blockages in the coronary (heart) arteries cause heart attacks and blockages in the arteries of the legs cause pain with walking or gangrene.

Diabetes is often associated with other problems such as high blood pressure and elevated cholesterol, which further increase the risk of atherosclerosis. Diabetes often accelerates the development of atherosclerosis such that it can appear in patients as young as 30 to 40 years of age, where normally it is seen in patients over 70.

Sensory neuropathy (loss of sensation) in the foot is another common complication of diabetes that increases the likelihood of ulcers and infection. Because the diabetic patient may have no pain from an ulcer, appropriate treatment is often delayed leading to a high risk of amputation. Fortunately an intensive program of preventative care and prompt referral to physicians specializing in diabetic disease can minimize the risk of limb loss. The diabetologist, vascular surgeon, and podiatrist comprise the multidisciplinary team best able to care for these problems.

Signs and Symptoms of Vascular Disease

As mentioned above, loss of sensation in the foot puts the diabetic patient at risk for foot problems. Ulcers can occur from unrecognized foreign bodies in the shoe, poorly fitted shoes, untreated foot deformities associated with diabetes, and poor circulation. Many diabetic patients with normal circulation still have problems with foot ulcers but when the cause is determined and treated these ulcers should heal promptly. However, when the circulation is reduced due to atherosclerosis ulcers may heal slowly or not at all. In severe cases the circulation is so poor that one or more toes become gangrenous (turn black). Infection may also occur with or without ulceration and in patients with reduced circulation, inadequately treated infection is the most common cause for amputation. The presence of gangrene, non-healing ulcers, or persistent infection often indicates that poor circulation is present and is an indication for prompt referral to a vascular surgeon.

Milder forms of arterial blockage can cause exertional pain in the legs. This pain, called claudication, is a tightness or cramping sensation that occurs in the calf or thigh after walking. It occurs after a consistent level of exercise (i.e. 1 or 2 city blocks) and is relieved by rest. This is a benign condition that carries a minimal risk of ultimate limb loss. Surgery is usually performed only for severe symptoms. A program of regular exercise and risk factor control (i.e. control of high blood pressure and elevated cholesterol, smoking cessation) is the initial treatment and usually leads to improvement.

The following list summarizes the “Danger Signs” of infection or poor circulation in diabetic patients.

1) Foot or leg ulcers that don’t heal

2) Foot gangrene

3) Blue, white, or deep red discoloration of the foot

4) Increased swelling or redness around an ulcer

5) Continuous pain in the foot relieved by standing or hanging the foot off the side of the bed

6) Persistent fluid drainage from the foot

7) Foul odor

Prompt consultation with a vascular surgeon should be sought if any of these signs or symptoms is present.

Treatment for Arterial Blockages

The term “severe arterial insufficiency” is applied to patients with blockages in the arteries severe enough to cause ulcers or gangrene. If untreated the condition usually progresses such that more and more of the foot becomes involved and eventually leads to amputation. These patients are especially susceptible to infection and if it occurs can lead to rapid tissue destruction, amputation, and even risk of death if inadequately treated. The main objectives of surgical treatment are to remove dead or infected tissue and restore normal circulation so the foot can heal.

The surgeon assesses the circulation to the foot using a variety of methods. Often physical examination is all that is needed to make a diagnosis of severe arterial insufficiency. The surgeon feels for pulses along the leg and examines the appearance of the foot. Absences of pulses and dry thinned-out skin of the foot lacking hair is indicative of poor circulation. A pressure measurement using a blood pressure cuff on the ankle is often used and compared to the arm. A reading of 40% or less of the arm pressure indicates severe arterial insufficiency.

If the surgeon makes a diagnosis of arterial insufficiency in the setting of ulcers or gangrene then surgery is indicated to improve blood flow, which will facilitate healing and prevent amputation. Prior to performing surgery, an arteriogram (or angiogram) is performed. This is an outpatient procedure performed in the radiology department whereby a catheter is placed in the leg artery at the groin level and dye is injected. X-rays are taken during the dye injection and these indicate the location and extent of the blockages. Using this information the vascular surgeon plans the appropriate operation to bypass the blocked vessels and maximize the blood flow to the affected area of the foot. Other tests may also be obtained prior to surgery. Since diabetic patients with vascular disease have a high incidence of heart disease, tests to assess heart function are often performed to determine the level of risk from surgery.

The specific operation depends on the location and severity of blockages. Typically a segment of vein is removed from the inner aspect of the leg (called the saphenous vein) that lies just underneath the skin. The upper end of the vein is connected to the artery above the blockage, usually in the groin, and the lower end to an artery below the blockage. This “arterial conduit” then provides normal blood flow to the leg and foot beyond the blocked vessels. Sometimes an artificial tube is used, made of modified Teflon material, when the blockage is only limited to the thigh area. The artificial tubes don’t last as long as vein grafts and are more prone to infection. The saphenous vein is also used to bypass diseased heart arteries during open heart surgery and can be removed without long term problems.

Outcome After Surgery

Modern vascular surgery is very successful at restoring circulation and preventing amputation. The overall success rate of surgery is greater than 90%. This may be reduced if the patient has had leg veins removed during cardiac surgery or from a vein stripping procedure. In these cases we may use vein segments from the arms that often need to be spliced together. Such procedures take much longer and have a reduced success rate. Slightly reduced success is also seen with patients who have already had previous surgery on their legs and have recurrent blockages.

Problems patients note after surgery include wound healing difficulties and leg swelling. Patients with diabetes and particularly those who are obese frequently have healing problems and infection of their leg incision. Leg swelling is common after vascular surgery but improves over the course of months.

Statistically 70 –80% of bypass grafts are still functional after 5 years. Some grafts may require another operation due to the development of narrowed areas from scar tissue. We routinely monitor bypass grafts using ultrasound every 6 months after surgery and will repair narrowed areas to prevent ultimate graft occlusion and failure.

Prevention of Vascular Disease

Although diabetes cannot yet be cured, patients can still take steps to reduce their risk of developing vascular disease in the future as well as preventing foot ulcers and infection. As mentioned above, risk factors for the development of vascular disease include high blood pressure, elevated cholesterol, smoking, and family history. Close follow up with your physician and diligent treatment of high blood pressure, elevated cholesterol, and diabetes will help minimize the risk. Smoking among diabetic patients is particularly harmful as this combination can dramatically accelerate the progression of atherosclerosis and increase the risk of amputation despite aggressive surgical treatment. Exercise is beneficial at reducing the progression of vascular disease and the risk of heart attack.

For patients with diabetes and neuropathy, meticulous foot care is critical to preventing ulcers that can lead to infection. These patients should wear properly fitted shoes with socks. They should not walk barefoot and need to check their shoes for stones and other foreign bodies before slipping them on. Regular foot and nail care by a podiatrist is beneficial.

Future Prospects

There has been tremendous growth in noninvasive vascular technologies that allow treatment of blockages using catheters, balloons, and stents without the need for making incisions. However this technology has limited applications in treating blockages in the small vessels of the legs that are commonly seen in diabetic patients. The most likely major development will be of drug and genetic therapies that treat the disease of atherosclerosis and either halt or even reverse its progression. Undoubtedly advances in the management of diabetes will play a crucial role in this.