ABC | Volume 114, Nº3, March 2020

Original Article Exercise Intensity during 6-Minute Walk Test in Patients with Peripheral Artery Disease Breno Quintella Farah, 1 Raphael Mendes Ritti-Dias, 2 Polly Montgomery, 3 Gabriel Grizzo Cucato, 4 Andrew Gardner 3 Universidade Federal Rural de Pernambuco, 1 Recife, PE – Brazil Universidade Nove de Julho - Programa de Pós-Graduação em Ciências da Reabilitação, 2 São Paulo, SP – Brazil Penn State College of Medicine, 3 Hershey – USA Northumbria University, 4 Newcaslte Upon Tyne – Reino Unido Mailing Address: Andrew W. Gardner • Department of Physical Medicine and Rehabilitation, Penn State College of Medicine, 500 University Drive, P.O. Box 850, Mail Code HP28, Hershey, PA 17033. E-mail: agardner4@pennstatehealth.psu.edu. Manuscript received January 24, 2019, revised manuscript April 23, 2019, accepted May 15, 2019 DOI: https://doi.org/10.36660/abc.20190053 Abstract Background: Non-supervised ground walking has been recommended for patients with symptomatic peripheral artery disease (PAD). However, the magnitude of the effort required by this activity and the characteristics of patients whose ground walking is more intense are unclear. Objectives: To determine whether ground walking exceeds the ventilatory threshold (VT), a recognized marker of exercise intensity, in patients with symptomatic PAD. Methods: Seventy patients (61.4% male and aged 40 to 85 years old) with symptomatic PAD were recruited. Patients performed a graded treadmill test for VT determination. Then, they were submitted to a 6-minute walk test so the achievement of VT during ground ambulation could be identified. Multiple logistic regression was conducted to identify predictors of VT achievement during the 6-minute walk test. The significance level was set at p < 0.05 for all analyses. Results: Sixty percent of patients achieved VT during the 6-minute walk test. Women (OR = 0.18 and 95%CI = 0.05 to 0.64) and patients with higher cardiorespiratory fitness (OR = 0.56 and 95%CI = 0.40 to 0.77) were less likely to achieve VT during ground walking compared to men and patients with lower cardiorespiratory fitness, respectively. Conclusion: More than half of patients with symptomatic PAD achieved VT during the 6-minute walk test. Women and patients with higher cardiorespiratory fitness are less likely to achieve VT during the 6-minute walk test, which indicates that ground walking may be more intense for this group. This should be considered when prescribing ground walking exercise for these patients. (Arq Bras Cardiol. 2020; 114(3):486-492) Keywords: Walk Test/methods; Peripheral Arterial Disease/complications; Physical Exertion; Exercise; Intermittent Claudication; Vital Capacity/physiology. Introduction Peripheral artery disease (PAD) affects approximately 12% of older adults in the United States 1 and 21.6% of the elderly population in Brazil. 2 Patients with symptomatic PAD (intermittent claudication) have impaired walking capacity, 3 lower muscular strength, 4,5 and several comorbid conditions. 6 In addition, patients with symptomatic PAD present poor cardiorespiratory fitness evidenced by lower peak oxygen consumption (VO 2 ) and worse walking economy than age‑matched controls. 7 Therefore, in these patients, walking performed during everyday activities are done at relatively higher intensities than in age-matched controls. Ventilatory threshold (VT) is an important marker of exercise intensity. Higher VT indicates that patients can sustain an increase in anaerobic metabolism during exercise. 8 In symptomatic PAD patients, lower VT is associated with lower walking tolerance and greater disease severit. 9,10 In addition, VT is most likely to be achieved before the onset of claudication pain. 11,12 Ground walking have been widely used to assess walking impairment in PAD patients through a 6-minute walk test, as this is a main clinical outcome in this group. 13 Recently, it has also been used in home-based exercise programs. However, the intensity in which ground walking is performed by patients with PAD is unknown. From a practical point of view, understanding the magnitude of effort in the 6-minute walk test might support the use of over-ground as an exercise modality in PAD patients. Thus, the purpose of this study was to describe the intensity of the 6-minute walk test according to VT in patients with symptomatic PAD. We also analyzed the predictors of the achievement of VT during the 6-minute test. Methods The procedures of this study were approved by the Institutional ReviewBoard at the University of Oklahoma Health Sciences Center (protocol #2337). A written informed consent was obtained from each patient prior to their participation. 486