Peripheral arterial disease (PAD) is a type of peripheral vascular disease (PVD) – a group of diseases that affects the body’s blood vessels (arteries, veins and capillaries). Peripheral arterial disease describes all of the conditions that can affect the arteries of the body outside of the heart (within the heart, these conditions are called coronary artery disease or CAD).

The vast majority of PAD conditions are caused by atherosclerosis (“hardening of the arteries”), this process by which plaque deposits slowly form on the inside walls of arteries. Atherosclerosis is also the process responsible for nearly all of the coronary artery disease (CAD) in the United States. CAD, also referred to as heart disease, is the number one cause of death in America. Coronary artery disease is atherosclerosis that occurs in the small coronary arteries supplying the heart muscle with oxygen-rich blood. When these arteries are blocked, the heart muscle dies (heart attack).

PAD is closely linked to CAD because of the nature of atherosclerosis. Researchers have discovered that atherosclerosis is a widespread disease, often present throughout the whole arterial system. When atherosclerosis is discovered in one artery, it is likely present in other arteries. While atherosclerosis in many areas of the body may not be dangerous or produce symptoms, it does create a higher likelihood that significant and dangerous disease exists in more critical areas. For that reason it is important to be aware of all the symptoms and dangers of both cardiac atherosclerosis and peripheral atherosclerosis. 

Not all PAD is caused by atherosclerosis. There are a variety of other conditions that may affect the peripheral arteries, but these conditions are responsible for less than 10 percent of all cases of symptomatic PAD. These other causes of PAD include blood clot or embolism, vasculitis (inflammation of the blood vessels), aortic dissection, and tumor (extremely rare). 

Atherosclerosis is a degenerative process that occurs in the lining of the arteries. It begins as a small plaque or “blemish” on the wall of the artery called a lesion. In the early stages, this lesion is harmless or benign. As the disease progresses, the lesion grows in both size and complexity, becoming a mixture of cells (e.g. smooth muscle cells, inflammatory cells), cholesterol crystals and calcified tissue. As this mixture grows, there is less room within the artery through which blood can flow. In response, the artery expands to keep the width of the artery normal. When the lesion progresses into its most advanced stages, the artery can no longer expand to accommodate the growing plaque lesion and the plaque begins to narrow the lumen (the space within the artery). This is referred to as stenosis or occlusion of the affected artery.

In addition to blocking the artery, the plaque may become unstable. In this case, there is the increasing possibility that pieces of plaque may break off and travel down the artery (an embolism). These pieces continue to travel until they lodge in a smaller artery and block the flow of the blood to the tissues and organs beyond the blockage. Alternatively, the body may identify the ruptured plaque deposit as an injury and a blood clot can rapidly form over the site. In either case, the supply of oxygen-rich blood will be limited beyond the obstruction, causing the rapid death of tissue and organs.

The consequences of PAD vary greatly based on the artery and organ system it affects. Diagnostic tests to diagnose the location and extent of the disease, as well as appropriate treatments, also differ. It is beneficial to examine the particular area of blood vessels (“circulatory bed”), such as the brain or kidneys, when describing symptoms, testing and treatment.

The major areas where atherosclerosis produces symptoms in the peripheral artery beds are:

Another possible consequence of atherosclerotic arterial disease is the formation of an aneurysm. This generally occurs in the aorta, which is the central artery of the body, or the “trunk” of the arterial tree. Aortic aneurysm is a significant cause of death in the United States, with over 15,000 deaths each year. The vast majority of these deaths (more than 95 percent) are preventable if the aneurysm is detected. Unfortunately, aortic aneurysms frequently do not have symptoms, and the first indication is a rupture. Less commonly, an aneurysm can form in the popliteal and femoral arteries of the legs. This generally occurs without warning or prior symptoms

The likelihood of acquiring PAD increases with age. Nearly 20 percent of Americans over the age of 65 have PAD, yet studies have shown that only 25 percent of these patients are undergoing treatment. Researchers believe this low figure is due to the widespread belief that symptoms of PAD are part of the normal aging process. In reality, the vast majority of diagnosed patients are able to control this progressive condition with proper medical treatment.