Peripheral Artery Disease Mays, Casserly, and Regensteiner C H A P T E R 15 Peripheral Artery Disease Mays, Casserly, and Regensteiner Chapter 03

Disease Definition Peripheral artery disease (PAD) refers to the blockage of the leg arteries by plaque, leading to gradual narrowing of the arteries in the lower extremities. The resulting stenoses, or occlusions (or both), lead to a decreased blood flow to the muscles of the leg.

Scope 8 to 12 million adults have PAD in the U.S. 35% to 40% of PAD patients have intermittent claudication (IC), which is reflective of pain, cramping, or aching in the calves, thighs, or buttocks. 1% to 2% of PAD patients experience critical limb ischemia. (continued)

Scope (continued) Patients with PAD have an increased risk of cardiac and cerebrovascular disease. Medicare costs associated with PAD were estimated at $4.37 million in 2001. Common risk factors associated with PAD are diabetes and smoking.

Pathophysiology Process of PAD begins with endothelial damage Risk factors for PAD are similar to those for coronary artery and cerebrovascular disease: smoking, diabetes, hypertension, hypercholesterolemia, high triglyceride levels, high leukocyte count, high homocysteine and fibrinogen levels, increased blood viscosity, and elevated C- reactive protein. (continued)

Pathophysiology (continued) Series of events after the endothelial damage are similar to those for coronary artery disease and are discussed in more detail in chapter 12. The presence of IC symptoms is dependent on the degree of stenosis in the arteries.

Clinical Considerations Initial assessment of patients with suspected PAD is completed with measurement of ankle-brachial index (ABI), which is discussed in more detail later. Patients with PAD should be treated similarly to those with heart disease in respect to risk factor reduction. Supervised exercise testing is commonly used to assess the severity of PAD. (continued)

Clinical Considerations (continued) Other invasive and noninvasive procedures can be used to assess PAD, and surgical interventions can be used in severe conditions

Signs and Symptoms As previously mentioned, IC is the most common symptom once the disease process reaches a certain point. More commonly, IC occurs with physical exertion and diminishes with rest. Calf pain is the most common place for reporting IC. (continued)

Signs and Symptoms (continued) IC associated in the thigh and buttock region can be more indicative of disease in profunda femoris and internal iliac. Chronic ischemia is associated with more severe PAD (arterial occlusive disease) and can lead to presence of ischemia at rest, foot ulcers, or gangrene. (continued)

Signs and Symptoms (continued) Accepted scales for PAD Fontaine stages I: Asymptomatic IIa: Mild claudication IIb: Moderate to severe claudication III: Ischemic rest pain IV: Ulceration or gangrene (continued)

Signs and Symptoms (continued) Rutherford categories 0: Asymptomatic I: Mild claudication 2: Moderate claudication 3: Severe claudication 4: Ischemic rest pain 5: Minor tissue loss 6: Major tissue loss

History and Physical Exam See table 15.1 for components of medical history important in assessment of a patient with peripheral artery disease. See table 15.2 for a summary of primary components of physical exam in patients with peripheral artery disease.

Diagnostic Testing Two primary categories are pressure (hemodynamic) studies and imaging studies Hemodynamic studies provide functional information, and imaging studies provide anatomic detail. ABI is used to assess pressure differences between the brachial artery and dorsalis pedis and posterior tibial arteries using blood pressure cuffs and a doppler probe. Refer to table 15.2 for normal to severe PAD. (continued)

Diagnostic Testing (continued) Other hemodynamic studies: Toe pressure Segmental limb pressures Pulse volume recordings Transcutaneous oxygen pressure (continued)

Diagnostic Testing (continued) Imaging studies CT angiography MR angiography Advantages and disadvantages of noninvasive imaging Invasive angiography typically performed as a preamble to planned interventional procedures based on diagnostic findings of noninvasive studies and is considered the gold standard for infrapopliteal and small vessel anatomy of the foot. (continued)

Diagnostic Testing (continued) See table 15.4 for a summary of advantages and disadvantages of noninvasive imaging using computed tomography or magnetic resonance angiography.

Exercise Testing Helpful for defining functional limitations Valuable tool in prescribing exercise (walking) when using a treadmill Cardiovascular and functional testing Useful in patients who present with symptoms of IC (typical and atypical) but have a normal resting ABI (continued)

Exercise Testing (continued) Completed with a standardized treadmill protocol, where ABI is completed before and after exercise. Abnormal study when the ankle pressure drops by >20% from baseline. Typical exercise protocol is constant speed of 2 mph, 2% grade increase every 2 minutes; endpoint is patient’s tolerance to leg pain. (continued)

Exercise Testing (continued) Treadmill testing useful for assessing claudication onset time or distance and peak walking time or distance. Approximately 16% of patients with PAD are unable to complete treadmill walking for various reasons. Other tests to asses PAD are arm and leg ergometry, stair stepping, and active pedal plantar flexion. (continued)

Exercise Testing (continued) Six-minute walking test useful in predicting the patient’s functional capacity based on the distance that can be completed. Other tests that have been shown to be valid and reliable measurements of FC in PAD patients are incremental and constant- speed shuttle walking tests.

Table 15.5

Treatment Two categories: Optimal medical treatment: Revascularization (surgical bypass vs. endovascular techniques) Optimal medical treatment: Antiplatelet agent (aspirin or clopidogrel) Assessment and treatment of all risk factors (lifestyle modifications and drug therapy management) Specific to the symptom of IC, Cilostazol is currently the only drug shown to improve IC walking distance (54%) (continued)

Treatment (continued) See table 15.7 for pharmacological treatment of peripheral artery disease. See table 15.8 for endovascular and surgical options for the revascularization of various arterial segments of the lower extremity. See figure 15.3 for an anatomic evaluation of 68-year-old diabetic male with a non- healing wound on the great toe of his right foot.

Exercise Prescription Special considerations for PAD Intermittent claudication Mode: walking Duration: work up to 50 minutes combining rest and exercise Intensity: dependent on the onset of IC (3 or 4 on the Claudication Symptom Rating Scale) followed by rest or a decreased workload until IC resolves (intermittent training) (continued)

Exercise Prescription (continued) Special considerations: Intensity: use of Borg 15-category scale or other walking perceived exertion scales (e.g., OMNI Walk/Run Scale) with successful endovascular therapy or bypass surgery Supervised vs. unsupervised setting

Exercise Training: Benefits Increased walking distance Increased distance at claudication onset Reduction in adverse CV event risk Low-intensity training appears beneficial compared to high-intensity training Intensity guided by IC symptoms appears to be most recommended Supervised vs. unsupervised exercise training appears to be gold standard therapy for patients with PAD and IC As patients exercise at higher intensities, attention should be focused on potential CVD symptoms due to high incidence of CAD

Exercise Training

Increased Walking Distance in PAD Patients Increased angiogenesis and collateral circulation, resulting in increase blood flow Reduction in blood viscosity Increased blood cell filterability and decreased RBC aggregation Attenuation of atherosclerosis (continued)

Increased Walking Distance in PAD Patients (continued) Increased extraction of oxygen and metabolic substrates resulting from improvements in skeletal muscle oxidative metabolism Increased pain tolerance Improved endothelial function Improved carnitine metabolism

Conclusion Inclusion of exercise is an important treatment option for PAD patients due to low risk and high benefits. The exercise physiologist needs to be aware of concomitant diseases associated with PAD. (continued)

Conclusion (continued) Supervised exercise training improves patient’s health and is also cost effective, but currently lacks insurance reimbursement. Additional research is needed to improve the effectiveness of these programs, particularly from the standpoint of increasing ease of adoption and long-term adherence.