Patients with lower extremity peripheral arterial disease (PAD) have increased functional impairment and increased rates of decline in lower extremity functioning compared with persons without PAD.1,2 In a cohort of 740 men and women with and without PAD, cross-sectional analyses demonstrated that fewer than 40% of participants with an ankle-brachial index (ABI) less than 0.40 walked continuously for 6 minutes compared with more than 95% of participants with a normal ABI.1 Among 470 participants with and without PAD, those with baseline ABI <0.50 were more than 12 times more likely to become unable to complete the 6-minute walk test without stopping at the 2-year follow-up compared with those with a normal baseline ABI.2 An important goal for the management of PAD is to improve PAD-related walking impairment and slow functional decline.
Substantive evidence demonstrates the benefits of supervised walking exercise rehabilitation for improving treadmill walking performance in patients with PAD and intermittent claudication.3 For patients with intermittent claudication, clinical trial data show that supervised walking exercise programs improve maximum treadmill walking distance by approximately 150%.3 Current clinical guidelines for patients with PAD recommend supervised walking exercise programs to improve PAD-associated walking impairment.4
Before beginning a walking exercise program, patients with PAD should undergo exercise stress testing. Graded exercise treadmill testing is a standardized, objective measure of walking endurance for patients with PAD and intermittent claudication that assesses changes in walking performance in response to exercise and other interventions. When performed before beginning an exercise rehabilitation program, treadmill testing can identify patients with coronary ischemia who require additional cardiac evaluation before entering an exercise program. Graded exercise treadmill testing is also used to determine the initial treadmill exercise prescription for patients with PAD. Typically, the initial exercise intensity is determined based on the treadmill speed and grade at which the patient first develops leg symptoms during baseline treadmill testing.
In this issue of the Journal of Cardiopulmonary Rehabilitation, Garber et al5 report results of their study comparing a Bruce protocol treadmill exercise test with arm-leg ergometry testing in 20 men and women with PAD. Garber et al suggest that because of the limiting effects of claudication symptoms during treadmill exercise, arm-leg ergometry could potentially be more sensitive to maximal aerobic exercise capacity in patients with PAD and intermittent claudication. In Garber's study, each of the 20 PAD participants performed a Bruce protocol exercise stress test and arm-leg ergometry testing on 2 separate occasions, separated by 12 to 14 days. The arm-leg ergometry exercise test consisted of 3-minute stages, in which increases in workload (power output) were achieved by increasing the revolutions per minute (RPM). The RPMs were increased to approximate the metabolic equivalents of the stages in the modified Bruce protocol. However, power output increased exponentially with increases in RPM, suggesting that increases in workload were not perfectly matched between the 2 methods at each exercise stage. Results of exercise stress testing between the 2 modalities were compared. At peak exercise, heart rate, systolic blood pressure, oxygen uptake (VO2), and the rating of perceived exertion were not significantly different between the 2 stress testing modalities. However, important differences in the 2 modes of exercise testing were observed. Claudication symptoms were more frequently responsible for test termination during treadmill exercise testing than during arm-leg ergometry testing. Claudication pain severity of >=3 on a scale of 0 to 4 was the reason for test termination in all 20 participants during treadmill testing, but in only 13 participants during arm-leg ergometry testing. The remaining 7 participants stopped exercise due to fatigue on the arm-leg ergometer. Furthermore, 3 participants experienced no claudication symptoms on the arm-leg ergometer but developed moderate to severe claudication during treadmill testing. Four participants who developed mild to moderate claudication during the arm-leg ergometer test had more severe leg symptoms during treadmill testing. Additionally, among the 13 participants who developed moderate to severe claudication on both exercise tests, onset of claudication symptoms occurred later during arm-leg ergometer testing (469 +/- 224 seconds) compared with treadmill testing (329 +/- 199 seconds). Finally, during the first 3 stages of exercise stress testing, mean heart rate, VO2, and severity of claudication symptoms were significantly higher during treadmill testing as compared with arm-leg ergometer testing. Ten of the 20 study participants completed stage 4 of the arm-leg ergometer protocol. However, only 2 completed stage 4 of the treadmill protocol.
Thus, exercise treadmill testing was more sensitive to the effects of claudication symptoms on exercise performance than arm-leg ergometry testing. The inclusion of upper arm exercise in arm-leg ergometer testing is likely responsible for the poorer sensitivity of the arm-leg ergometer test to claudication-limiting symptoms. Although lower extremity functioning is reduced in patients with PAD compared with those without PAD, previous study demonstrates that upper arm performance is not simultaneously reduced in persons with PAD compared with those without PAD.6 By diverting energy expenditure away from walking performance and incorporating upper body exercise, the arm-leg ergometer became less sensitive to walking-related claudication symptoms in patients with PAD. Although the authors hypothesized that incorporation of upper arm exercise would result in a better estimation of aerobic capacity, measures of aerobic capacity were not significantly different between the 2 modes of testing. Thus, although arm-leg ergometry may be a reasonable alternative for measuring maximum aerobic capacity in some PAD patients, results from the study of Garber et al suggest that it should not substitute as a measure of walking performance in PAD.
Several aspects of the study by Garber et al limit its generalizability. First, arm-leg ergometry testing was compared with a Bruce exercise stress test protocol. Patients with severe PAD may need to begin treadmill exercise testing at a slower treadmill walking speed than required by the Bruce stress testing protocol. It is unclear how the arm-leg ergometer would compare with treadmill exercise stress testing in PAD patients who require an initial treadmill speed of 0.50 miles per hour, for example. Second, the investigators did not compare changes in exercise performance in response to an intervention between the arm-leg ergometer and the treadmill test. It is not clear whether the 2 stress testing modalities are similarly sensitive to changes in maximum aerobic capacity or improvement in claudication symptoms in response to an intervention. Third, the test-retest reliability of the arm-leg ergometer in persons with PAD was not assessed.
Although Garber et al conclude that arm-leg ergometry may be a useful alternative to treadmill exercise for detecting PAD, their data do not support this assertion. In patients with borderline or low-normal ABIs, measurement of the ankle systolic pressure before and after treadmill walking exercise may uncover PAD because in patients with lower extremity arterial obstruction, the ankle systolic pressure typically drops 20% or more during treadmill exercise and takes more than 2 minutes of rest to return to baseline.7,8 Individuals without lower extremity atherosclerotic disease have no decline in ankle pressure during treadmill exercise. Participants in the study by Garber et al had baseline resting ankle brachial indexes of less than 0.90, indicating established PAD. No data were provided on changes in ankle systolic pressure in response to arm-leg ergometry testing in patients with ABI values of 0.90 to 1.00, for example. Thus, further study is necessary to determine whether arm-leg ergometry testing is a useful alternative to treadmill exercise testing for unmasking PAD in patients with a borderline or low-normal ABI.
Few therapies have demonstrated efficacy for improving lower extremity functioning and walking performance in persons with PAD. New therapies for improving walking performance in patients with PAD are needed. A recent randomized controlled clinical trial of 104 PAD patients with intermittent claudication demonstrated that arm cranking exercises and leg cranking exercises, respectively, improved maximal walking distance and time to onset of claudication symptoms during a shuttle walk test.9 The shuttle walk test is a measure of walking performance that is measured in a hall corridor. For novel forms of exercise in PAD patients, such as those incorporating upper extremity aerobic exercise, the arm-leg ergometer exercise test may be a useful measure of changes in aerobic capacity in patients with PAD. However, changes in arm-leg ergometer exercise testing in response to these novel therapies, both with regard to aerobic exercise capacity and claudication symptoms, should first be compared with changes observed during graded treadmill exercise testing in patients with PAD.
In conclusion, in a small number of PAD patients with intermittent claudication, the arm-leg ergometer appears to be comparable to a Bruce protocol treadmill associated exercise stress test for measuring peak exercise performance and aerobic capacity in patients with PAD and intermittent claudication. However, the arm-leg ergometer is less sensitive to PAD-related limitations in treadmill walking performance than the treadmill exercise testing. Further study is needed to determine whether the arm-leg ergometer provides useful clinical data beyond that provided by treadmill exercise testing in patients with PAD. Further study is also needed to determine whether in some settings, arm-leg ergometry may be a meaningful alternative to treadmill exercise testing.
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