What is Peripheral Arterial Disease (PAD)?
Peripheral arterial disease (PAD) is a condition in which there is a build-up of plaque inside the major arteries in the body, particularly affecting those arteries that carry blood to your head, major organs, arms and legs. The plaque consists of an accumulation of cholesterol, calcium and fat. This causes the arteries to narrow as well as lose their suppleness and elasticity and become hardened. This process of arterial hardening and narrowing is called atherosclerosis.
Atherosclerosis reduces the amount of oxygen-rich blood that is circulated to your vital organs and other parts of the body. The plaque can often become inflamed, unstable and may rupture causing a blood clot to form in that area, resulting in major reduction of the downstream circulation. The is often the underlying mechanisms for major conditions such as heart attacks, strokes and critical/sudden reduction in blood supply to the legs.
Atherosclerosis of the heart arteries (Coronary Artery Disease) is classified separately from Peripheral Arterial Disease but the underlying process is the same for both problems.
What are the risk factors for PAD & Atherosclerosis?
There are several risk factors that can lead to PAD. These include, but are not limited to:
- Smoking (this is the main risk factor along with Diabetes).
- Obesity (BMI >30)
- High cholesterol levels blood pressure
- Increasing age
- High Blood pressure
- A family history of atherosclerosis (peripheral artery disease, heart disease or stroke)
- Renal/Kidney disease (particularly if already on hemodialysis)
- Poor eating habits
Symptoms of Peripheral Arterial Disease
Many people who have underlying PAD don’t exhibit any symptoms or mistake their symptoms as being due to some other cause (eg. Arthritis etc). The most common symptoms involve the lower limbs where people may experience:
- Claudication (Painful cramping in the buttock region, thigh or calf muscles after activity)
- A cold leg/foot when compared to the other side
- Non-healing minor wounds on the foot/lower leg
- Slowing or loss of hair and/or nail growth on the lower leg/foot
- Erectile dysfunction in men
- If involving the arteries supplying the brain, TIA (Transient Ischemic Attacks), also known as ‘mini-strokes’ or large stroke
- In cases of severe PAD, the pain in the foot can start to occur when at rest or lying down. This is known as ischemic rest pain and is often helped by hanging the legs over the side of the bed at night or having to get up and walk around the room
Diagnosis of PAD
The diagnosis is based on a review of your symptoms and physical examination by the doctor or vascular specialist. The examination usually consists of checking the pulses around the body, including the arms, neck, abdomen and legs. The quality and presence of pulses will often, but not always, act as a good guide as to whether there is any significant underlying peripheral vascular disease. In addition, a stethoscope may be used to listen for any bruits, (noise cause by turbulent blood flow that results for an underlying narrowing or stenosis in the artery). In addition, the colour of your hands and feet and other subtle signs (hair growth on the legs, quality and health of nails etc) offer useful information to aid with the diagnosis.The blood pressure in both arms is often checked and can be compared and contrasted against the blood pressure in the leg, around the level of the ankle, a bedside test known as an Ankle Brachial Pressure Index (ABPI or ABI). If the PAD is moderate to severe and requires intervention to help alleviate the symptoms, further tests such as CT scans, MRI scans and Ultrasounds may be required to help plan surgical intervention.
Ankle Brachial Pressure Index (ABPI or ABI)
- This is the most common bedside investigation performed by the Vascular Specialist. The test directly compares the blood pressure in the arms to the blood pressure at the legs, around the level of the ankle. It is a painless exam, which if done correctly, can often accurately diagnose and confirm the diagnosis of PAD.
- In healthy patients without underlying PAD, the blood pressure at the ankle should be the same as that in the arms, such that the ratio is close to 1.0 (normal value between 0.9 and 1.2)
- This suggested that there is the same volume/pressure of blood in the legs as in the arms
- When the pressure at the ankle is reduced compared to the arms, that ratio (ABI) is reduced.
- An ABI between 0.5-0.9 indicates PAD that is likely to be symptomatic , usually in the form of claudication, and may need surgical intervention.
- An ABI of 0.4 or less is usually associated with critical peripheral arterial disease and warrants urgent surgical intervention to minimise the chance of gangrene or amputation.