Peripheral Artery Disease - What You Should Know

What You Should Know About Peripheral Artery Disease (PAD)

Imran Afridi, MD, FACC, RPVI

Dallas Heart and Vascular Consultants

www.dallasheartandvascular.com

Arteries are muscular tubes that carry nutrient and oxygen rich blood from the heart to the entire body including brain, limbs and organs. Peripheral Arterial Disease (PAD), also known as peripheral vascular disease (PVD,) is a medical condition in which arteries become blocked due to build up of fat and cholesterol inside their walls thus limiting blood flow (Figure 1).

This process is also known as atherosclerosis and can affect arteries in any part of the body including the heart itself (coronary artery disease).

This article will focus on PAD that affects arteries of the legs. This is a very common, frequently unrecognized, cause of leg pain and if untreated can lead to gangrene and loss of limb.

The purpose of this article is to provide information on who is at risk, what are alerting symptoms of Peripheral Artery Disease, who should be screened for it, and how is it diagnosed and treated.

Prevalence

Estimates of US population with PAD vary from 4-12 million people or nearly 2-3% of the population. Both men and women are at risk and the incidence increases with age rising from 5% in 50-59 year olds to 16% in age group 60-75 and over 25% in those 80 years or older. The prevalence is even higher in those with risk factors for the disease.

For example among diabetics or smokers age 50-69 nearly one out of three have some degree of Peripheral Artery Disease. With out screening many individuals at risk are not diagnosed in time to prevent progression and present with late consequences of the disease such as serious leg infection or gangrene.

Causes

PAD is caused by atherosclerosis or build of plaque inside the wall of the artery that narrows the lumen thus reducing blood flow. The plaque is primarily composed of cholesterol, inflammatory cells along with fibrous tissue and calcium. The primary risk factors that lead to atherosclerosis are:

Smoking
Diabetes
High blood pressure (Hypertension)
High cholesterol
Older age

In addition, obesity, sedentary life style, and family history of atherosclerosis also increase risk of developing PAD. Frequently, PAD co exists with other forms of atherosclerotic diseases.

In patients undergoing treatment for PAD two out of three also have coronary artery disease. Those who have suffered other forms of atherosclerotic diseases such as stroke or heart attack should be evaluated for PAD.

Signs and Symptoms

The classic symptom of PAD is claudication which is discomfort in the leg that occurs on walking or climbing and is eased after resting. Typically patients complain of aching, heaviness, cramps or numbness involving buttock, thigh, calf or foot depending on the location of the blockage in blood flow.

There are many other signs and symptoms that suggest presence of PAD such as weak pulses in legs on exam, ulcers or sores that fail to heal, and coldness of the affected leg or foot.

Another common manifestation of Peripheral Artery Disease, particularly in diabetics is erectile dysfunction which occurs due to narrowing of blood vessels in pelvis reducing blood flow to penis. A small number of people present with sudden pain and coldness of a foot or leg.

This suggests that a clot has formed inside the affected artery with complete loss of circulation. This is a medical emergency and requires immediate attention.

It is important to recognize that only 10-15% of those with PAD present with classic claudication. Another 20-30% can be identified by other signs and symptoms. However 50% of people affected by PAD have not obvious symptoms and have silent disease.

It is therefore important for patients and their physicians to recognize who is at risk for PAD and consider PAD screening evaluation of those at high risk of the disease.

Who should be screened

The American Heart Association and American College of Cardiology identify the following individuals as at risk for PAD who should be considered for screening:

Age less than 50 with diabetes and one other risk factor (smoking, high cholesterol or high blood pressure)
Age 50-69 with diabetes of history of smoking
Age 70 or older
Symptoms of leg pain suggestive of PAD
Abnormal leg or foot pulses on exam
Other forms of atherosclerotic diseases such as stroke, or heart attack

Diagnosis

There are many tools for evaluation of PAD. The simplest method is ABI or ankle brachial index. This involves measurement of blood pressure in the arm and at both ankles (Figure 2). ABI is calculated as ratio of ankle pressure to arm pressure. An ABI of 0.9 to 1.3 is normal.

This is a non invasive, quick and reliable method to screen for Peripheral Artery Disease. Usually if ABI is abnormal the next step is to perform an ultrasound examination of the leg arteries, also known as arterial Duplex. It allows visualization of the inside of the arteries and measurement of blood flow.

This test helps in localizing the site of artery blockage and estimating severity and provides guidance for treatment. The final step in evaluating PAD is usually a peripheral angiogram or arteriogram. This is a specialized exam that involves placing a small tube in a leg artery and then injecting dye and taking X-ray movie of the circulation (Figure 3).

This allows assessment of precise location and extent of PAD that is required for selecting the optimal treatment. Other ways to identify PAD include special forms of CT and MRI scanning.

Treatment

The primary goals of managing Peripheral Artery Disease are relief of symptoms and prevention of progression and complications. In addition it is also important to include in the goals a comprehensive assessment and treatment of risk factors, evaluation of other co-existing atherosclerotic diseases such as coronary artery disease and life style education.

Medical treatment for PAD is aimed at controlling risk factors, using blood thinners and medication for reducing symptoms. Treatment of risk factors typically includes cholesterol lowering medications called statins, and blood pressure medications.

Patients with Peripheral Artery Disease are generally recommended to take aspirin daily to reduce risk of complications such as heart attack, stroke or loss of leg circulation from clot formation.

In selected patients other stronger blood thinners such as clopidogrel or warfarin may be recommended. In patients with PAD that have symptoms of leg pain medications are prescribed that may improve symptoms and increase the distance one can walk before symptoms occur.

In patients with severe disease, particularly those with severe symptoms, non healing ulcers or gangrene definitive treatment usually involves angioplasty. Angioplasty or PTA (percutaneous transluminal angioplasty) is a procedure that involves placing a special tube or catheter at the site of blockage in the artery, usually via a blood vessel in the groin. The catheter has a collapsed balloon at its tip.

Once the catheter tip is at the site of blockage, the balloon is inflated to break up the plaque. In some cases a metallic coil, called stent, is placed inside the artery to prevent is from collapsing. There are many variations of the procedure including use of laser to dissolve plaque or applying a special plaque cutting device (atherectomy).

The specific procedure used is dependent of technical factors and decided by the cardiologist performing the treatment.

In a small sub set of patients, catheter based techniques are not feasible and treatment requires open surgery with a bypass of the blocker artery either using blood vessel from another part of the body or synthetic material.

Contrary to popular belief, use of high potency vitamins, mineral supplements and chelation therapies are not helpful in treatment of Peripheral Artery Disease and not recommended.

Prevention

The key to preventing Peripheral Artery Disease or reducing its progression is adopting a healthy life style that includes smoking cessation, low cholesterol diet and regular exercise. Those with claudication can frequently improve symptoms by regular exercise, either treadmill or track walking.

The American Heart Association recommends walking at speed and/or incline that brings on claudication in 3-5 minutes. Once symptoms occur, rest until relief, then exercise again. Such a regimen done for 30-40 minutes, 3-5 times a week, is shown to improve claudication distance.

Those with PAD who continue to smoke have a four fold higher risk of developing further disease despite aggressive treatment.

The desirable cholesterol goal for patient with Peripheral Artery Disease is to keep the “bad cholesterol”, also known as LDL cholesterol less than 100 mg/dl, and the lower the better. In certain high risk individuals LDL of less than 70 is the target.

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