- November 19, 2019
- Posted by: cmcdonald
- Category: Peripheral Artery Disease
Peripheral Arterial Disease (PAD), also known as peripheral vascular disease, happens when blood vessels narrow and restrict blood supply to the body’s peripheral limbs and organs. This narrowing of the blood vessel lumen (space inside the vein or artery) leads to an inadequate supply of oxygen and nutrition to peripheral areas. This can lead to ischemia (reduced blood flow) and organ damage. PAD raises the risk of stroke and heart attack. Limbs are most commonly affected by Peripheral Arterial Disease, with legs affected eight times more than arms.
Incidence and prevalence of PAD
An estimated 8.5 million people in the United States have Peripheral Arterial Disease. People over age 50, in particular, are at risk for this condition. As one of the most common cardiovascular diseases, PAD affected 118 million people worldwide in 2017.
The PAD-related mortality rate has increased by 57.8% in a decade, resulting in 70,200 deaths globally in 2017 compared to only 45,087 deaths in 2007. Two main factors are responsible for PAD’s high mortality rate, the lack of screening programs and the asymptomatic course of the disease.
Peripheral Arterial Disease Pathology
The blood vessel’s lumen’s gradual narrowing deprives the peripheral tissues of their nutrients and oxygen supply, which promotes ischemic tissue damage. The tissue ischemia releases VEGF (vascular endothelial growth factor, a signal protein) to start forming new blood vessels (called angiogenesis), which helps compensate for decreased blood flow to the ischemic tissue. This, in part, restores the blood supply to the ischemic area and decreases the severity of the disease.
Typically, the vein or artery’s interior must be more than 70% blocked before symptoms occur. While the body’s own compensation process may reduce the severity of symptoms below 70% blockage, tissue damage still occurs if:
- Physical exertion strains a normally symptom-less patient’s blood “demand to supply gap,” leading to ischemia.
- Rupture of plaque (fatty deposit) occurs, leading to limb-threatening consequences.
- An embolus (mobile plaque) plugs the already stenosed vessel resulting in a sudden and complete occlusion of the blood vessel.
PAD Risk factors
Peripheral Arterial Disease shares common risk factors with Coronary Artery Disease (CAD—or coronary heart disease). Risk factors include:
Atherosclerosis accounts for 90% of narrowed blood vessels (arterial stenosis) or blockages (occlusions). Atheroma, a sticky fatty tissue that accumulates on the inner surface of arteries, makes blood vessels hard and stiff. After a long-time, the fatty plaque becomes part of the vessel wall or it may dislodge from larger arteries into smaller arteries. This phenomenon is called an embolism.
Normal blood pressure is essential to cardiovascular health. Increased blood pressure thickens the muscular layer of arteries, causing them to harden and become unadaptable to changes in blood pressure. This inelasticity narrows down the arterial lumen and results in Peripheral Arterial Disease.
About 5-10% of people with PAD are diabetics. People suffering from diabetes have a problem using blood sugar to generate energy to help break down fatty deposits. This makes them vulnerable to a myriad of diseases due to high circulating levels of sugar, triglycerides, and other fats.
Cigarette smoking, a modifiable risk factor for PAD, causes more cases of Peripheral Arterial Disease than Coronary Artery Disease. Smoking causes endothelial dysfunction, disrupts coagulation, and affects platelet function, which multiplies the risk of PAD 7 times.
Clinical Manifestation of Chronic PAD
Chronic arterial occlusion presents along a broad spectrum but divides into 3 progressively severe categories:
- Asymptomatic disease (no symptoms felt)
- Intermittent claudication
- Critical limb ischemia
Signs and symptoms vary with each category and other factors, such as the site and onset of occlusion, size of the artery, and the area it supplies. Since the lower limbs are most commonly involved in PAD, we discuss the symptom phases for these below.
Physical exertion, such as walking or running, may cause pain or fatigue in lower limb muscles. The distance between taking the first step where the pain is typically absent and the onset of pain is called the claudication distance. It represents a measure of the severity of the disease.
Critical limb ischemia
Compared to intermittent claudication, caused by occlusion of single vessels and partially or completely compensated by collateral blood flow, critical limb ischemia is caused by multiple lesions affecting different arterial segments down the leg.
Ischemic rest pain
Rest pain typically develops in the forefoot and is characteristically worse at night. This stems from reduced circulation in the skin and subcutaneous tissue as blood pressure and cardiac output are lower at night and lying down alters the effects of gravity on limbs. When pain awakens a patient at night, it may be relieved by hanging the limb off of the bed. At this point in the disease, even a minor injury to the foot will often fail to heal—resulting in ulcers, gangrene, and limb loss.
Patients with PAD may present with painful non-healing ulcers in the distal foot and toes.
If you or a loved one has a non-healing wound, please contact American Endovascular & Amputation Prevention today to schedule a consultation.
Loss of blood supply eventually leads to the death of the tissues and gangrene.
Erectile dysfunction can also occur as a consequence of PAD. The involvement of both hypogastric arteries may contribute to impotence and decrease sperm count.
In the setting of mild ischemia, the sensory function remains intact in nations with PAD. In patients with severe ischemia, a sensory loss may occur. In general, if patients have isolated sensory loss or pins and needle sensation in the toes, they are more likely to have peripheral neuropathy.
Signs of chronic lower limb PAD
Ankle-brachial pressure index (ABPI)
Ankle-brachial pressure index represents the ratio of blood pressure in the ankle to that in the arm. In healthy individuals, this pressure is the same, with an ABPI value of 1 or greater. In chronic lower limb PAD, the blood pressure of the ankle is diminished as compared to the blood pressure in the arm.
In people with intermittent claudication, the ABPI is typically 0.5-0.9 and in critical limb ischemia, ABPI is less than 0.5. A value of less than 0.3 is indicative of imminent necrosis and gangrene of the tissue.
The ischemic limb is usually cold but in some cases, it can be warm if the ischemia is mild.
The pulse rate increases in response to exercise in normal individuals. In patients with PAD, the pulse may disappear with exercise.
Chronic ischemia of soft tissue can cause atrophy of the muscles supplied by the artery affected by PAD.
The decreased blood supply to the periphery produces a loss of hair, skin scaling, and thickening of nails due to slowed keratin turn over.
Doctors work not only to find the cause of PAD but to assess the severity of the disease.
Since atherosclerosis is the most common cause of PAD, a physician orders test to learn causative factors for atherosclerosis and look for related complications. These include:
- Blood tests to exclude anemia, diabetes, and renal disease.
- Lipid profiles to see the LDL, cholesterol and triglycerides concentration.
- Platelet counts and coagulation profiles to check for hypercoagulable states.
- EKGs/ECGs (heart tracing) and echocardiography (heart ultrasound) to rule out any cardiac abnormalities that can potentiate PAD with an atheroembolic event.
Specific investigations are used to detect the site and severity of arterial obstruction. They also help in planning for surgical management if the disease has an advanced course.
Doppler ultrasound, a special type of ultrasound, measures blood flow in vessels. The Doppler ultrasound can only be used to check the presence of blood flow in the limb. It cannot tell if that flow is sufficient to ensure the survival of involved tissue.
Duplex scanning, an advanced form of Doppler ultrasound, is the gold standard for vascular flow studies. Although more expensive than a Doppler ultrasound, duplex scanning produces highly accurate color images of blood flow.
A CT angiogram gives a complete anatomical roadmap of the arterial system, checking the vessel wall abnormalities, anatomical lesions, and patency (openness) of the arteries. During CT angiography, a dye is injected into a vein and travels into the leg artery.
Digital subtraction angiography (DSA) is another technique in which dye is injected into the artery of the leg and multiple images are obtained of the blood vessels.
Treatment for Peripheral Arterial Disease
All patients with atherosclerotic vascular disease should be strongly urged to comply with best medical therapy (BMT). The patients who fail to respond to BMT due to non-compliance or advanced disease are then assessed for intervention.
Non-surgical, minimally invasive treatment options include:
This procedure has evolved with cutting edge advances including orbital, rotational, and diamond-coated surfaces technology as well as a laser to remove or modify plaque from a clogged blood vessel. The catheter is inserted via a minimally invasive incision in the artery. Atherectomy is particularly useful for treating arteries or blood vessels that are not easily treated with stents.
Angioplasty uses a low profile catheter with an inflatable balloon to stretch the affected artery open. The balloon is used to stretch the affected artery open, restoring blood flow.
A host of different metallic based implantable devices will be inserted into the artery to provide a new skeletal framework to strengthen the walls and help it remain open. Some of the stents may have drug eluding properties to prevent blood clotting and increase longevity. In certain circumstances, some stents may have woven mesh or a covered wall to increase longevity and durability.
Thrombectomy is used to treat blood clots that block blood flow. The procedure entails a catheter inserted through a nearby artery in order to vaporize or extract the clot.
PAD treatments have progressed considerably in the past five years. New endovascular therapies and technologies can significantly improve the lives of people affected by PAD and prevent the progression of this disease.
American Endovascular can help.
Our commitment to minimally invasive, non-surgical procedures puts us at the forefront of the next wave of endovascular care. Early intervention of Peripheral Artery Disease can save a limb. If you or someone you know suffers from symptoms of PAD, please contact us today for a consultation.
Drug-eluting stents: potential applications for peripheral arterial occlusive disease