Wikipedia:Osmosis/Peripheral vascular disease



Author: Tanner Marshall, MS

Editor: Rishi Desai, MD, MPH, Tanner Marshall, MS

With peripheral vascular disease, vascular refers to the blood vessels, and peripheral means the outer limits or edge of something, which in this case refers to essentially any vessels that aren’t supplying the heart or the brain, like the legs, arms, or other organs. Peripheral vascular disease is when one of these arteries becomes narrowed, which reduces blood flow, and this often affects the limbs.

Peripheral vascular disease, or PVD usually involves the arteries, and so sometimes it’s also referred to as peripheral artery disease or PAD. PVD is most often caused by a blockage, called organic PVD, most commonly caused by atherosclerosis, which is a buildup of lipids and fibrous material just under the inner lining of the blood vessel, called the tunica intima. When plaque builds up, it narrows the artery, which reduces perfusion to whatever tissue it tends to supply, this buildup usually happens over the course of years. Also though, the vessel could be blocked by an embolus, which can happen suddenly if a blood clot from some upstream artery lodges in a peripheral artery, which obviously stops blood flow from getting to the tissue the vessel supplies.

Besides organic PVDs though, there are also functional PVDs, where blood vessels stop blood flow by changing diameter, like with vasospasms, where the vessel constricts and blood flow is reduced. This type is usually short term and can come and go.

The most commonly affected vessels in peripheral vascular disease are the arteries supplying the legs, so when less blood gets to the muscle tissue in the legs, that tissue sees less oxygen and becomes ischemic. Ischemic cells release adenosine, a type of signaling molecule, which is thought to affect nerves in these areas, which is felt as pain. This pain in the legs is often referred to as claudication.

Sometimes, even though it’s narrowed, at rest there’s enough blood to meet the tissue’s demands, and many people are usually asymptomatic.

But if the person is walking or exercising then the leg muscles start to work harder and demand more oxygen, so demand becomes greater than what’s being supplied, which causes the claudication or pain.

The location of the pain is a clue on which artery’s involved—if it’s the hips and the buttocks, think lower aorta or iliac, if it’s the thigh, think iliac or common femoral artery, for the upper ⅔ of the calf, the superficial femoral artery, the lower 1/3—the popliteal artery, and finally for the foot—think tibial or peroneal artery.

Other symptoms include leg or foot wounds or ulcers that don’t heal up normally, as well as color changes of focal areas of the skin. So for example, if the leg’s been affected, the foot might turn pale white when it’s raised, called elevation pallor—since gravities sort of working against bloodflow to the lower extremities, which already has a hard time getting through the narrowed artery.

Likewise, the foot might turn red when it’s lowered—called dependent rubor, since gravities working with the bloodflow.We can see that gravity seriously starts to affect blood flow in the affected arteries.

As that arterial blockage gets bigger, less and less blood gets to the tissues, which can lead to more serious complications. First, rest pain describes a continuous burning or pain in the forefoot and toes when the legs are elevated, and then the pain is relieved when they’re lowered, like hanging the feet over the bed or walking around the room, which allows more blood to get down to the foot. If the blockage is severe enough, then the limb might be at risk of gangrene, death of the tissue, because without oxygen for long enough, the cells can actually die, or necrose. In which case the dead tissue would likely have to be removed—and in some cases the limb would have to be amputed.

The major risk factors and causes of peripheral vascular disease are the same as those for atherosclerosis, the same process that, if involved in the neck arteries—can cause a stroke, and if involved in the coronary arteries, can cause a myocardial infarction, or heart attack. Smoking seems to be the biggest contributor to PVD, but other diseases and conditions are also linked to a higher risk of PVD, like diabetes, dyslipidemia or an abnormal amount of lipids in the blood, and hypertension.

Diagnosing PVD usually involves listening to the pulse in the iliac arteries of the legs with a stethoscope. Since that artery’s been narrowed, it can make a whooshing sound, called a bruit. Another test that can be done is a doppler ultrasound, which is a non-invasive way of visualizing blood-flow.

The most common test though to diagnose peripheral artery disease is the ankle-brachial index, or ABI, where blood pressure is taken in the ankle and in the arm, and then compared. Peripheral artery disease is typically diagnosed if the systolic blood pressure in the ankle divided by the systolic blood pressure in the arm is less than 0.9.

In general, claudication is often seen in people with an ABI between 0.4 and 0.9, rest pain is seen between 0.2 and 0.4, and tissue loss, ulcers, and gangrene between 0 to 0.4.

Treating PVD often requires significant lifestyle changes that address the underlying risk factors, like quitting smoking, for one, as well as adopting healthy eating habits and exercising regularly. Alongside these, though, sometimes people with PVD will also get certain medications that typically aim to reduce the likelihood of blood clotting and obstruction of the blood vessels, surgical intervention like angioplasty or bypass surgery is rarely needed.