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Results of a 305-patient trial indicate ischemic leg pain could serve as a threshold for whether or not a patient with peripheral artery disease will see a meaningful improvement in walking score from their walking routine.
Patients with peripheral artery disease (PAD) who do not experience ischemic leg pain during their walking program could be failing to reach a threshold that provides any meaningful benefit, according to the results of a new trial from Northwestern Medicine.
Results of the study demonstrate participating in a low-intensity exercise program failed to achieve a meaningful difference compared to no exercise at all, while high-intensity walking that induced ischemic leg symptoms was associated with significant improvements in 6-minute walking distance and walking impairment at 12 months.
"We've shown you have to walk to elicit ischemic leg pain to reap the benefits," said lead investigator Mary McDermott, MD, professor of medicine at Northwestern University Feinberg School of Medicine, in a statement. "It will lessen over time, and most people eventually will be able to walk further without discomfort."
After a previous study found pain during exercise was a primary reason cited for inability to continue a walking program, McDermott and team designed the Low-Intensity Exercise Intervention in PAD (LITE) randomized clinical trial to assess whether a low-intensity walking exercise intervention that does not induce ischemic leg pain improved walking distance in patients with PAD compared to a high-intensity intervention inducing ischemic leg symptoms and a nonexercise control group.
Funded by a grant from the National Heart, Lung, and Blood Institute of the National Institutes of Health, the LITE trial randomized 305 patients in a 120:120:65 ratio using a SAS computer program between September 25, 2015 and December 11, 2019. These patients were recruited from 4 US medical centers and followed for 12 months after randomization. Of note, the final follow-up occurred on October 7, 2020.
To be included in LITE, patients needed to have an ankle-brachial index (ABI) of 0.90 or less in either leg. Exclusion criteria for the trial included major amputation, a MiniMental State Examination score of less than 23, use of a walking aid other than a cane, having a walking limitation for a reason other than PAD, and having a significant visual or hearing impairment, among others.
Investigators received written informed consent from 441 patients with PAD and 305 underwent randomization. Of these, 116 patients were randomized to low-intensity walking, 124 were randomized to high-intensity walking, and 65 were randomized to the nonexercise control. The overall study population had a mean age of 69.3 (SD, 9.5) years, 47.9% were women, and 59.3% were Black. In total, 250 participants completed the 12-month follow-up.
Patients randomized to an exercise group were asked to walk for exercise 5 times per week for up to 50 minutes per session and wear an accelerometer to document exercise use intensity and time. For the purpose of analysis, the high-intensity group walked at a pace eliciting moderate to severe ischemic leg symptoms while the low-intensity group walked at a pace eliciting no ischemic leg symptoms.
The primary outcome for the trial was mean change in 6-minute walk distance at 12 months. Investigators pointed out a distance of 8-20 meters was used as a threshold for minimum clinically important difference at 12 months.
Upon analysis, investigators found 6-minute walk distance had changed from 332.1 meters at baseline to 327.5 meters in the low-intensity exercise group (within-group mean change, -6.4 meters; 95% CI, -21.5 to 8.8; P=.34) and from 338.1 meters to 371.2 meters in the high-intensity exercise group (within-group mean change, 34.5 meters; 95% CI, 20.1 to 48.9; P <.001) at 12-month follow-up. Based on these results, investigators determined the mean change for the between-group comparison was -40.9 m (97.5% CI, -61.7 to -20.0; P <.001).
In the nonexercise control group, 6-minute walk distance changed from 328.1 meters at baseline to 317.5 meters at 12-month follow-up p (within-group mean change, -15.1 meters; 95% CI, -35.8 to 5.7; P=.10), which investigators highlighted was not significantly different from the change observed in the low-intensity exercise group (between-group mean change, 8.7 meters; 97.5% CI, -17.0 to 34.4; P=.44).
A safety analysis revealed 2 serious adverse events were considered study-related. These events were a transient supraventricular arrhythmia developing after the baseline exercise stress test and needing to undergo coronary artery stent placement after chest discomfort developed while exercising in the low-intensity group.
McDermott and colleagues noted future plans to evaluate the biological expiation for the association between ischemia of the lower extremities and apparent benefit from walking exercise.
This study, “Effect of Low-Intensity vs High-Intensity Home-Based Walking Exercise on Walk Distance in Patients With Peripheral Artery Disease,” was published in JAMA.