PERIPHERAL ARTERIAL DISEASE: FACTS AND FIGURES
Some of the physical and emotional barriers reported by individuals having peripheral arterial disease (PAD) include burning sensation in the calves, needing to stop and rest at frequent intervals while walking, the inability to climb stairs, and an overall reported decrease in their quality of life. PAD is a common and serious chronic disease that increases the risk of myocardial infarction and stroke (2,3,6-8,10,17). An estimated 5 to 10 million American adults have PAD (2). PAD is basically systemic atherosclerosis, or global vascular disease, with many different areas of the body being susceptible. PAD affects 1 in 20 Americans older than 50 years (17), and PAD of the lower extremities affects 20% to 30% of older patients in general medical practices (15). PAD is a result of the buildup of plaque in the arteries of the legs but also can occur in the arteries of the head, kidneys, and stomach in a manner similar to atherosclerosis in the coronary arteries.
Similar to atherosclerosis, the presence of PAD is associated with abnormal cholesterol levels, hypertension, diabetes, and cigarette smoking (14,17). Approximately 15% to 40% of PAD patients also have intermittent claudication (IC) (cramping, heaviness) in their legs (2,6,7).
Cramping occurs most commonly in the calf muscles but also can occur in the posterior thighs and buttocks. Pain in the posterior thigh and buttocks generally indicates that arteries closer to the trunk are blocked and that the disease is more severe. Persons with IC typically experience heaviness, burning and squeezing, fatigue, limping, and pain of varying intensity in their lower extremities during weight-bearing activities such as walking and stair climbing.
IC pain is caused by a mismatch in the blood and oxygen supply/demand ratio in the working muscles. IC in the lower extremities is eliminated, and a temporary balance in the blood and oxygen supply/demand ratio is reestablished by resting in a sitting (non-weight-bearing) position. Many individuals with PAD and claudication, especially the elderly, are undiagnosed. Some symptoms of PAD and IC are often ignored or thought to be a result of aging or other conditions such as arthritis.
The pain of IC often causes those who experience it to avoid any and all forms of physical activity. Interestingly, IC symptoms seem to be more common in persons having atherosclerosis in arteries in other parts of their bodies (17). Many of those who have IC become homebound and physically dependant on other people (2). Attempts to avoid IC can reduce daily physical activity levels and precipitate a decline in fitness (2). Physical activity intolerance is generally caused by:
- increased blood viscosity (thickness)
- compromised leg blood flow and oxygen extraction
- skeletal muscle fiber changes that favor anaerobic metabolism
- skeletal muscle weakness
- inefficient walking gait (2,4,6,7,16,19).
Persons with PAD and without IC also generally encounter a reduction in walking capacity and stair-climbing ability compared with their premorbid (before disease) state because of general physical deconditioning (2). Some persons with PAD have sores and wounds that heal poorly because of compromised circulation to limbs; thus, PAD is a common cause of amputation (17). This is most common in persons with PAD who also have diabetes (17).
RISK FACTORS FOR PAD
The risk of developing PAD increases with age. Smokers and ex-smokers are four times more likely to develop PAD compared with nonsmokers, whereas one in every three persons with diabetes 50 years or older will develop PAD (17). African Americans are more than twice as likely to develop PAD as similarly aged white counterparts (17). The highest incidence of PAD is found in men who smoke (13). Other risk factors for developing PAD include an elevated serum cholesterol level; having a history of vascular disease, cardiovascular disease, or stroke (17); hypertension; and physical inactivity (2,11).
EXERCISE BENEFITS FOR PAD
Regular exercise and physical activity (primarily walking) can provide substantial benefits for individuals with PAD. The most notable is the enhanced ability to walk further/longer, faster, and with less claudication. The same is true for stair climbing. For example, it seems that persons with PAD who walk at least three times weekly demonstrate significantly smaller reductions in walking pace and distance (15). The effects of supervised interval walking programs for persons with PAD/IC have been proven effective (1,7,10,11). Clients with IC who engage in supervised walking programs increase their initial claudication walking distances and absolute claudication walking distances by between 106% and 189%, and 64% and 80%, respectively (7,11). Initial claudication distance and absolute claudication distance refer to the walking distances when clients first experience claudication and experience claudication pain severe enough to stop exercising/walking and sit down, respectively.
Although the magnitude of these potential benefits varies among individuals with PAD, improvements in walking and stair-climbing tolerances (e.g., distance, duration) will result from regular participation in exercise and physical activity. Because most people with PAD have other cardiovascular disease risk factors (e.g., hypertension), modification of these risk factors is another potential exercise benefit. Exercise benefits for persons with PAD include an enhanced walking and stair-climbing ability; increased muscular strength, endurance, and flexibility; improved aerobic capacity (which leads to less dependence on anaerobic metabolism during tasks such as walking and stair climbing); and a lower risk of limb amputation (primarily in persons with diabetes). Additional benefits include a reduction in blood viscosity (thickness), improvements in other cardiovascular disease risk factors (e.g., diabetes, dyslipidemia), and a potential increase in leg blood flow (2,6-8,10,11,16,23).
GUIDELINES FOR INITIATING EXERCISE PROGRAMS FOR PERSONS WITH PAD
As previously mentioned, PAD is a cardiovascular disease, and the goals of an exercise program for those with PAD include reducing claudication pain (if present), reducing cardiovascular disease risk factors, increasing walking and stair-climbing capacities, and improving overall physical conditioning and physical activity tolerance (2-4,6-8,10,11,13,16,21). Exercise testing and training should not be conducted until clients receive medical clearance from their physician(s) (2,6). Because persons with PAD are considered high risk for cardiovascular disease(s), exercise participation should be preceded by a physician-supervised graded exercise test (GXT) with electrocardiography monitoring (2,6). This will detect any changes in heart rhythm and determine the onset of claudication pain and changes in claudication intensity. In case that an individual with PAD has a limited walking capacity because of severe pain and is unable to complete a treadmill GXT, a pharmacological (e.g., dobutamine, adenosine) stress test with routine monitoring of vital signs may be administered to detect myocardial ischemia or dysrhythmias (5).
Ankle-brachial index (ABI) is a method of assessing the severity of PAD and is expressed as the ratio of ankle to arm systolic blood pressure (2,17). After the patient assumes a supine position, a blood pressure cuff is placed just above the ankle (similarly to how it is done on the arm) and inflated until blood flow is temporarily stopped in the ankle. The cuff is deflated slowly until the initial sounds of blood flow are detected again. The first sounds of blood flow represent the systolic blood pressure. A Doppler ultrasound wand is used instead of a stethoscope to detect the sounds of blood flow and to improve precision and accuracy. This procedure is repeated on the other ankle inflated just above the ankle.
The brachial (arm) blood pressure is determined next in a similar fashion with the blood pressure cuff placed firmly around the upper arm (approximately 1 inch above the bend in the elbow). This is repeated on the other arm. The ABI is calculated by dividing the higher ankle systolic blood pressure by the higher brachial artery systolic blood pressure. Postexercise ABI can also be used to assess disease severity. Additional Doppler ultrasound techniques, without a blood pressure cuff, also can be used to determine which specific arteries are blocked. The ABI scores are generally compared with a standardized table to determine PAD severity. The ABI Scale appears in Table 1. Regarding the clinical usefulness of basal and postexercise ABI, Nielsen and colleagues (20) suggest that because of a wide range of blood flow to the extremities, pre-pressure and post-pressure drops may be associated with different types of exercise and that varying rest periods may favorably impact these changes. However, the authors also note that increases in rest times are not practical in outpatient settings. Recommended rest periods for individuals with PAD are summarized in Table 2.
Undetected heart disease also can be diagnosed by a physician-supervised GXT or pharmacological stress test. Persons with PAD should not participate in an exercise program if comorbidities (e.g., diabetes, hypertension) are unmanaged, poorly controlled, or might limit exercise tolerance (2,6). Clients/patients having concomitant peripheral neuropathy (numbness in feet) should have their feet regularly checked by their physician for blisters, cuts, and sores. Clients should also perform regular self-checks.
In addition, exercise professionals need to communicate to their clients/patients with peripheral neuropathy (commonly found in people with long-standing diabetes) the importance of always wearing shoes or some sort of protective footwear to protect their feet from what they cannot feel (e.g., broken glass). Persons with PAD are typically on a number of medications to manage their PAD and other comorbid conditions (3,4,6,17,18). They include antiplatelat drugs (e.g., warfarin) to reduce blood viscocity, angiotensin-converting enzyme inhibitors (e.g., enalapril) and angiotensin-converting enzyme inhibitor II receptor blockers (e.g., valsartan) to control blood pressure, β-blockers (e.g., atenolol) to control blood pressure, and numerous diabetic medications (3,4,17,18). Exercise professionals should understand the effects these medications can have on the exercise response of persons with PAD and their potential side effects and safety precautions (6,18). The reader is directed to the following reference for more specific information on medications (18).
Participants should remain in a clinically or professionally supervised exercise program until their physician determines their symptoms, risk factors, and comorbidities (if present) to be stable and/or absent (2). An estimated functional capacity of 7 metabolic equivalents (METS) (or measured >5 METS) or twice the level of occupational demand also is used as a criterion to progress patients with cardiac, pulmonary, or metabolic diseases from participation in clinically or professionally supervised exercise programs to independent or community-based exercise programs (2).
CLINICAL EXERCISE RECOMMENDATIONS FOR PAD
Because individuals with PAD are at high risk for medical complications during exercise, it is ideal that they begin their exercise program in a clinical environment (e.g., outpatient cardiac rehabilitation) (2). This way, patients will be supervised by the clinical staff (e.g., ACSM registered clincal exercise physiologists) who have training and experience specific to PAD and existing comorbidities. Monitoring vital signs (e.g., electrocardiography, heart rate, blood pressure, claudication pain) before, during, and after exercise is essential during the initial stages of exercise training to ensure patient safety. In addition, immediate access to emergency equipment (e.g., code cart, automated external defibrillator [AED]) is typically available in the event of a medical emergency. Exercising in a clinical setting that will likely facilitate timely contacts between physicians, clinicians, and patient, promoting appropriate communication and follow-up.
Once medically cleared to begin clinical exercise training, guidelines that have been established should be followed. Walking should be the emphasis of the exercise program (2,6). Stair climbing is another activity that can be very beneficial and should be incorporated, as tolerated. Other non-weight-bearing aerobic activities (e.g., cycling, upper-body ergometry) are beneficial but should not replace walking and/or stair climbing, unless necessary. A major goal of the exercise program is to reduce claudication, and walking is the most effective approach to accomplish this (1,2). Persons with PAD are encouraged to walk 3 to 5 days a week for an accumulated duration of 30 to 60 minutes per session (2). Interval walking protocols are well tolerated and are the exercise method of choice (2,6-8,10,11,21,23). The claudication (pain) scale is a visual tool to help clients express the severity of their claudication during activities such as walking (see Table 3). It should be taught to all clients with PAD before they initiate an exercise (or walking) program. Clients with PAD are encouraged to walk until their leg pain (claudication) reaches a level of 3 (intense pain) (1,2,6). Walking intervals should be followed by complete recovery periods that eliminate all pain. This procedure should be repeated until the total desired exercise duration for the session is achieved (1,2,6-8,11,21).
Resistance training (RT) may be implemented to increase muscular strength and endurance in the upper and lower extremities, which can help enhance the ability to perform activities of daily living. Resistance training is an important component of a complete conditioning program for adults with and without cardiovascular and other chronic diseases (9,16,19,22). However, RT should not be the emphasis of the exercise program and not replace walking or other types of aerobic activity. An RT program should resemble that for an apparently healthy individual, address strengthening all major muscle groups (2,9,19), and place special emphasis on the lower extremity muscles in the buttocks, thighs, and lower legs (16). Table 3 highlights exercise guidelines for individuals with PAD.
HEALTH AND FITNESS RECOMMENDATIONS FOR PAD
Fitness professionals should take a comprehensive approach in managing their clients/patients with PAD similarly to that of their clients with heart disease who may not be experiencing this disease. The most important part of the exercise prescription in this population is the specificity of training (21). With the lower extremities being the most common site of manifestation and symptoms (claudication), aerobic-type exercise, particularly walking, favorably impacts exercise capacity (tolerance) more than resistive-type exercise (10). Individuals with PAD will benefit from engaging in resistance training, however, this mode of exercise alone is not recommended. Furthermore, in designing exercise programs specific to this population, the exercise professional also should keep in mind cardiovascular (e.g., diabetes, hypertension) and noncardiovascular (e.g., orthopedic) risk factors that may exist in working with individuals with PAD.
Fitness professionals must understand the physiological barriers impacting exercise performance (tolerance) and the resulting impact on fitness level (objective) and pain threshold (subjective) in the PAD patient; these are important measures to be considered when developing the exercise prescription in this special population. Functional capacity in most people with PAD found in the clinical setting ranges between 3 and 4 METS. In other words, many PAD patients are only capable of tolerating exercise or physical activity at an intensity no greater than approximately 2 METS. Intermittent walking protocols should elicit initial claudication symptoms within 3 to 5 minutes and clients should be encouraged to continue walking until they experience IC symptoms equivalent to a 3 (intense pain) on the claudication scale (1). IC walking protocols can eventually serve as a platform for increasing exercise (walking) intensity. Interval training with specific duration goals is often prescribed for PAD patients with IC. With the goal of initial exercise time being 30 minutes in this population, and the long-term goal being up to 60 minutes in one exercise session; gradual, tolerated increases in exercise intensity of the same interval length can provide significant fitness benefits. With levels of physical fitness being a better predictor of mortality (death) than level of physical activity (12), individuals with any type of vascular disease or cardiovascular risk factors who increase their fitness level by either increasing their level of physical activity (when possible) or significant weight loss (usually possible) should experience improvements in their overall risk profile.
Mr. Smith is a 58-year-old engineer at an aviation plant. He recently had a physical examination because he was not feeling well. He was having difficulty maneuvering throughout the plant and climbing the numerous flights of stairs at the plant. He needs to cover between 3 and 4 miles on an average work day. He also is having trouble walking 18 holes of golf, which he plays twice a week. He has received medical clearance to start an exercise program.
These are the results from his physical examination:
- fasting glucose, 110 mg/dL
- body mass index, 28 kg/m2
- blood pressure 130/80 mmHg; controlled
- sedentary lifestyle
- current cigarette smoker; attending a smoking cessation program at a local hospital
- ABI 0.85
- Increase walking capacity-increase time to onset of claudication and maximal claudication; increase total walking distance and walking speed.
- Increase overall physical function-increase muscular strength and endurance, joint flexibility and stair climbing ability.
- Weight loss.
- Lower blood glucose and blood pressure.
Exercise program: Table 3 provides the exercise guidelines for initiating and progressing Mr. Smith's exercise program.
Exercise is medicine for PAD. The achievable benefits an individual with PAD can obtain from regular exercise and physical activity are important for health-related quality of life. There are specific guidelines that must be followed when initiating and progressing an exercise program to promote safety and success. In addition, realistic expectations and goals should be developed. However, the health-related quality of life benefits achieved from exercise make this "medicine" hard not to take!
CONDENSED VERSION AND BOTTOM LINE
Peripheral arterial disease is a debilitating disease that can be effectively managed with medications and regular exercise and physical activity. Although exercise results can vary, improved walking ability, less claudication, enhanced functional abilities, reduced risk of limb amputation, and lower risk of cardiovascular disease are achievable benefits from proper exercise training.
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