Published: Nov. 20, 2006
Updated: Mar. 11, 2011
Who among us hasn’t experienced aches or pain in our legs after a long walk or hours of gardening on hands and knees?
But when debilitating leg pain occurs after a short walk from the car to the store, it often signals a serious problem -- atherosclerosis, a condition in which fatty material collects along the walls of arteries.
This fatty material hardens into plaques that can form in the arteries in the legs, neck, kidneys, and even the intestines, restricting blood flow as they grow. When blockage occurs in the leg arteries, the most common site outside of the heart, it’s known as peripheral artery disease, or PAD.
People with the hallmark symptom of PAD, intermittent claudication -- leg pain during exercise that abates with rest -- often think the problem is a normal sign of aging.
Unchecked, the condition may progress to critical limb ischemia, a severe blockage of the arteries that seriously decreases blood flow to the extremities, with a high risk of gangrene and amputation.
Moreover, PAD is often a harbinger of life-threatening cardiovascular events.People who have intermittent claudication, gangrene, or undergo amputations because of critical limb ischemia typically don’t die directly from these conditions -- instead, they die of heart attacks or strokes, and this fact underscores the need to provide comprehensive care to address both the immediate problem and prevention.”
It’s estimated that more than 8 million Americans over age 40 have PAD. Most don’t realize they have it because nearly 75 percent have no overt symptoms or mistake them for something else.
The most reliable noninvasive screening test is the ankle brachial index (ABI). The 15-minute test employs a Doppler stethoscope to determine the ratio of the systolic blood pressure reading in the ankle to that in the arm (obtained the traditional way).
An ABI less than 0.9 is abnormal, and the lower the number, the greater the blockage -- and the greater the risk of critical limb ischemia, heart attacks, and strokes.
Along with obtaining an ABI, vascular technicians at Duke often take segmental blood pressures at various sites on the leg and the toe and pulse volume recordings, which provide a qualitative assessment of blood flow. The tests are especially informative in patients whose arteries are calcified and hard to compress, resulting in artificially high blood pressure readings.
Other diagnostic tests that pinpoint the location and extent of the blockage include ultrasound, computed tomographic or magnetic resonance angiography, and X-ray angiography using contrast dye, which remains the gold standard for vascular imaging.
The risk factors for PAD parallel those for heart disease: diabetes, tobacco use, hyperlipidemia (such as high cholesterol and high triglyceride levels), and high blood pressure. ABI screening is recommended for everyone with diabetes over age 50, and other high-risk groups -- the elderly, current smokers, African-Americans, and people with reduced kidney function -- should also be considered for screening.
• PAD risk factors parallel those for heart disease and include diabetes, tobacco use, high cholesterol, and high blood pressure
• Screening is recommended for everyone with diabetes over age 50
• Other high-risk groups -- the elderly, current smokers, African-Americans, and people with reduced kidney function -- should also be considered for screening
PAD management strategies include:
• Smoking cessation
• Aggressive control of diabetes
• Control of cholesterol levels
• Dietary changes, such as a low-saturated-fat and low-cholesterol diet; weight loss if needed
• Exercise training to help improve blood flow to the legs and improve pain-free walking distances
• Good blood pressure control to reduce the risk of heart attack and stroke
• Medications to diminish the risk of blood clot formation, heart attack, and stroke, as well as slow the progression of PAD
In the case of disabling claudication or critical limb ischemia (with its specter of amputation), invasive measures to increase blood flow may be necessary. Depending on the location and severity of the blockage, treatment options include balloon angioplasty, often with stenting; a variant using a low-temperature balloon (cryotherapy); and plaque-excising atherectomy.
For severely obstructed arteries, surgery may be required to clear out or bypass the blockage, notes vascular surgeon Jeffrey Lawson, MD, PhD. PAD was traditionally the purview of vascular surgery before less invasive procedures became more common, Lawson adds, and he and fellow vascular surgeons continue to offer PAD patients a host of medical therapies, surgical options, and stenting, depending on the nature of the blocked artery and the patient’s needs.
The SilverHawk plaque excision system has become a popular alternative to angioplasty among Duke’s interventional radiologists and cardiologists. The working end of the catheter used during the procedure contains a rice grain-sized carbide cutting blade that shaves and collects the plaque lining the artery.
Duke researchers are pursuing therapeutic angiogenesis--promoting the growth of new, healthy blood vessels to increase blood flow to the legs. In one study, vessel growth in rabbits was successfully jump-started by injecting their legs with a gene-containing plasmid, a circular unit of DNA. The gene codes a protein responsible for activating the gene for vascular endothelial growth factor, a substance made by cells that stimulates new blood vessel formation.
Another innovative treatment being tested involves a type of adult stem cell responsible for developing blood vessels early in life and repairing them in adulthood. Bone marrow is harvested from a patient with critical limb ischemia who has no other treatment options. The stem cells are isolated, then injected into the patient’s calf. Early results are promising.
Plans are to continue expanding the multidisciplinary approach to PAD and other vascular diseases at Duke, through research and by integrating conventional and experimental therapies. Promoting awareness and increasing the diagnosis of PAD are top priorities of Duke’s Peripheral Vascular Disease Program.