Peripheral vascular disease
Causes and associated conditions
There are many conditions obstructing blood flow to the limbs. However, the most common cause by far is atherosclerosis, which results in narrowing of the artery due to fatty deposits on the inside of its walls. These fatty, cholesterol-containing plaques prevent normal blood flow and may grow so large that they totally block the artery, shutting off the blood supply to the limb.
Atheromatous plaques form in all arteries, so patients with PVD nearly always have plaque in their heart arteries too. Major risk factors for PVD are thus the same as for heart disease in general:
- family history of PVD or heart disease
The characteristic symptom of PVD is Intermittent claudication: this means pain in the affected region (arm or leg), which is brought on by exercise and relieved by rest. As the disease progresses, there may be pain even at rest when the blockage becomes critical. Many patients gain relief of pain by sitting with the affected foot hanging down over the side of the bed. Total blockage can lead to gangrene if an alternative blood supply is not available. If the disease affects arteries of the intestine, pain is felt when the bowel is active immediately after eating.
The main site of obstruction also influences symptoms, which arise in parts of the limb below the blockage, which are deprived of normal blood flow. Thus, a blockage near the knee may cause calf pain, but one higher up near the groin will cause pain in the whole leg.
Disease in head and neck arteries may cause dizziness, transient ischaemic attacks, or even a stroke.
In diabetes, even the very small vessels are affected, including those which provide blood supply to the peripheral nerves, which themselves then lack adequate oxygenated blood. During exercise like walking, a diabetic may thus not experience intermittent claudication, because his nerves are damaged and he can no longer feel the pain. Diabetics thus often do not feel angina as a warning of heart disease.
A clear description by the patient of intermittent claudication makes this a clinical diagnosis, which is confirmed by the following findings on examination:
- poor/absent pulses below the narrowing
- audible murmur over the site of the obstruction
- a cool limb with shiny skin
- poor wound healing
- hair loss and nail changes
- in severe cases, ulceration or even gangrene.
Tests done to assess the PVD, and plan management, include:
- ankle/arm index, which compares blood pressure in the ankle and arm before and after exercise
- ultrasound of the obstructed part of the limb
- MRI scan gives a clear picture of the diseased areas
- arteriography: this is an invasive procedure in which dye is injected into the arteries, and video X-rays are taken to show the blockages. This is usually done only in preparation for surgery.
- full cardiac assessment by a cardiologist – this is crucial, because PVD patients nearly always have coronary artery disease as well, which could be more immediately life-threatening, and thus need treating even before managing the PVD.
Unless the blockage is critical, most patients are first treated medically in the following way:
1. The most important first step is to modify risk factors
- stop smoking immediately
- lower blood pressure
- lower cholesterol
- manage diabetes if present
2. Exercise: mild, and increasing gradually within the tolerance of the patient, may help to open up new routes of blood supply to the limb. The benefits persist for as long as the patient continues with regular exercise.
3. Medication: Most important here is Aspirin, alone or in combination with other drugs also affecting platelets: these prevent clots forming on the cholesterol plaques, which may block the artery completely.
4. Other: Balloon angioplasty may be used to open a blockage. This is done by inserting a thin catheter into the artery and inflating a balloon at the site of obstruction to force it open again. This can then be kept open by inserting a stent.
In patients who do not respond well to medical therapy (continued pain), or whose disease progresses despite full medical therapy, or who have critical blockages, surgery is performed.
The commonest procedure is to bypass the narrowed part of the artery with a graft; the graft may be an artificial artery or a vessel removed from elsewhere in the patient’s body. Recently, successful stenting of even small peripheral vessels in diabetics has been done. Stents in carotid arteries to the brain are also done with good results.
In severe cases, bypass or stenting may not be possible and amputation of the limb may be necessary.
Disease in the aorta, the main artery of the body, is in a separate category and surgery here is a major procedure. Aortic vascular surgery often consists of repairing an aneurysm (a weakened part of the wall), which may have to be done as an emergency because of actual or imminent rupture. In some selected cases a stent may be placed in the aorta via a catheter, saving the patient open abdominal surgery.
With good treatment and strict risk factor control most patients will have improvement of symptoms. They will also have significant protection against heart disease and stroke. Up to 20% may have worse pain and 2% may need surgery. The worst outcome is in diabetics who continue to smoke, especially if they have pain at rest.
The most important step, especially with a positive family history, is to modify your risk factors. Of these, the single most important one is to never smoke, or to stop immediately if you do.
Dr AG Hall
The information provided in this article was correct at the time of publishing. At Mediclinic we endeavour to provide our patients and readers with accurate and reliable information, which is why we continually review and update our content. However, due to the dynamic nature of clinical information and medicine, some information may from time to time become outdated prior to revision.