Peripheral arterial disease and diabetes

Diabetes mellitus (DM) is a global disease affecting approximately 10% of the world population. Long standing diabetes in the body results in complications affecting almost all organ systems causing a multitude of disabling symptoms and disabilities. These complications include nephropathy (diabetes related kidney failure), vasculopathy (diabetes related arterial disease – heart, brain and limbs), retinopathy (eyes) and many more. Diabetic vascular disease affecting the coronary arteries can result in heart disease including myocardial infarction (heart attack). Peripheral Arterial Disease (PAD) in the diabetic population is a distinct disease that causes blockage of the arteries supplying blood to the legs and brain. PAD affecting vessels that supply the brain can result in stroke while PAD in the lower limb arteries may result in amputation and loss of limbs. These devastating complications often affect the middle aged diabetic population, which effectively robs them of their most productive years in life.

PAD – Signs and Symptoms

In the earliest stages of PAD, the patients are asymptomatic. In these situations, the presence of PAD is often detected during routine examination of diabetic patients. Such routine examination is generally recommended at least on an annual basis and includes examination of pulses in both feet. Any reduction or absence of foot pulses indicates the presence of early PAD which allows the physician to take necessary action including medication.

The first actual symptom that patients complain of with PAD is ‘intermittent claudication’. This is a cramping ache or pain occurring in the calf muscles or thighs typically brought about by walking. The pain occurs only while walking and disappears within 1-2 minutes of rest. The distance that the patient can walk before getting the pain is often constant and the pain is reproducible on walking again after rest.

More extreme presentations of PAD include rest pain (where there is severe foot pain even at rest) and tissue loss (where there is severe painful non-healing wounds, ulcers or blackening of toes). These symptoms are collectively referred to as Critical Limb Ischemia (CLI).

Diabetic Foot Ulcers

Presence of diabetes can lead to chronic non-healing wounds or ulcers in the legs, which if not treated properly, may result in a major amputation above or below the knee. The factors that contribute to diabetic ulcers include:

• Diabetic Peripheral Neuropathy

This causes dysfunction of sensory, motor and autonomic nerves in the legs and feet. The sensory nerve dysfunction leads to a foot that is numb and devoid of normal sensation causing repeated traumatization and wounding. The dysfunction of the motor nerves results in minor deformities of the foot and toes that in turn increase the possibility of repeated traumatization and pressure in certain vulnerable areas of the foot. The autonomic nerve dysfunction disrupts the normal protective mechanisms of the skin including sweating and hydration leading to a dry cracked skin prone to ulceration.

• PAD

Diabetes is a major risk factor for atherosclerosis. Atherosclerosis is a process that affects the arteries in the body causing deposition of substances in the inside of the arterial wall, thereby diminishing the diameter of the artery and thereby reducing the blood flow in that artery. In addition, diabetes also causes severe calcification of the arteries that diminish the functionality of the arteries. The end result is a significant reduction in the blood flow to the foot (ischaemia) that promotes and propagates ulcers.

• Increased Risk of Infection

Diabetes increases the risk of infection and reduces the inherent immune status of the individual. Hence, any pre-existing ulcer has a high risk of infection and these infections generally spread much more rapidly than in a person without diabetes.

All the above factors contribute to a situation where the diabetic individual has a ‘high risk foot’. This implies a foot that is devoid of the natural protective mechanisms, is more prone to get traumatized and wounded, has poor blood supply and thereby poor oxygen supply to heal any wounds and has a very high risk of rapid spreading infection. Therefore, in the presence of a wound, unless prompt action is taken to rectify the situation, the risk of losing the leg to an amputation is very high.

Diagnosis

The diagnosis of PAD in a diabetic depends mainly on clinical examination. Routine examination of foot pulses is the key to identifying any underlying PAD. This can be done by any doctor or care giver at any stage. In situations where further testing is required, a specialized scan such as Doppler, duplex scans and angiograms are used. However, these specialized scans are needed only in the presence of severe symptoms or CLI where definite interventions are planned.

Treatment

The treatment of diabetes related PAD depends on the severity of the condition.

In the asymptomatic individual where PAD has been diagnosed on a routine examination, the treatment includes identifying all other possible risk factors (hypertension, high cholesterol levels, smoking etc.) and controlling them. In addition routine medications to prevent progression of the symptoms are also used. Some of these medications include aspirin, anti-cholesterol tablets, etc.

In the patient who complains of intermittent claudication (calf pains), again treatment includes identification and control of all risk factors. Strict control of diabetes, control of blood pressure and cessation of smoking will greatly minimize the progression of symptoms and appearance of complications. In addition, above mentioned medications are also routinely prescribed to control disease progression.

In those patients where claudication is very severe that it disrupts day-to-day living and those who have CLI (rest pain, ulcers, gangrene etc.) will require definitive intervention to rectify the PAD. This involves scanning to identify exact location and degree of the disease and measures taken to re-establish blood flow to the foot (revascularization).

Revascularization of the affected leg can be by either peripheral angioplasty or surgical bypass operation. Angioplasty is usually reserved for those patients who are unsuitable for operations and have a limited life span. This involves introducing a wire in to the affected artery and ballooning it to increase its diameter and improve the blood flow. Occasionally this also requires an artificial stent to keep the blood vessel open long term and allow the symptoms to subside or wounds to heal.

Angiogram showing blocked arteries to the leg

Surgical bypass is a more robust and durable option for those suffering from severe diabetic PAD. This involves reconstructing the affected leg by creating a new blood vessel most often using the patient’s own veins. This procedure allows a healthy new channel to supply blood to the affected area. The long term durability of such a bypass is far superior to angioplasty especially in otherwise fit patients and overall results are more durable.

Successful control of risk factors and revascularization can alleviate the ischaemic symptoms in the leg and allow proper wound healing in diabetic PAD. This is the first and the most important step in preventing a major amputation. However, the treatment does not end here. In order to maintain blood flow and prevent repeated ulceration the patient needs to comply with the following:

• Continue all medications prescribed for preventing diabetic related complications including diabetic medication, aspirin, blood pressure medication and cholesterol medication
• Continue to avoid smoking and other risk behavior
• Protective specialized footwear – avoid barefoot walking and always wear a special diabetic footwear to protect against repeated wounding
• Regular follow up visit with the physician and surgeons to identify any problems early and take remedial measures