The Two-Minute Walk Test as a Measure of Functional Capacity in Cardiac Surgery Patients Dina Brooks, PhD, MSc, BSc (PT), Janet Parsons, MSc, BSc (PT), Diem Tran, BSc (PT), Bonnie Jeng, BSc (PT), Barbara Gorczyca, BSc (PT), Janet Newton, GAP, MSc, Vincent Lo, BSc (PT), Cheryl Dear, BSc (PT), Ellen Silaj, BSc (PT), Therese Hawn, BSc (PT) ABSTRACT. Brooks D, Parsons J, Tran D, Jeng B, Gorczyca B, Newton J, Lo V, Dear C, Silaj E, Hawn T. The two-minute walk test as a measure of functional capacity in cardiac surgery patients. Arch Phys Med Rehabil 2004;85: 1525-30. Objective: To examine construct validity and sensitivity of the two-minute walk test (2MWT) in cardiac surgery patients. Design: Measurements were made in patients preopera- tively, during the postoperative in-hospital stay, and 6 to 8 weeks after discharge from hospital. Setting: Ambulatory and hospitalized care. Participants: Patients (N=122; mean age  standard devi- ation, 639y) undergoing coronary artery bypass grafting. Interventions: Not applicable. Main Outcome Measures: The 2MWT, New York Heart Association (NYHA) functional classification for cardiac dis- ease, the Nottingham Extended Activities of Daily Living scale, and the Medical Outcomes Survey 36-Item Short-Form Health Questionnaire (SF-36). Results: Distance walked in 2 minutes decreased signifi- cantly postoperatively (from 13826m to 8433m, P.001), but increased again at follow-up (15131m, P.0001). Dis- tance walked on the 2MWT correlated significantly to SF-36 (physical function subscale) preoperatively (r=.44) and at fol- low-up (r=.48) (P.001). There was a significant difference in distance walked between those with NYHA class I and II compared with those classified as III or IV (P=.04). However, there was no significant difference in distance walked in 2 minutes between those who developed cardiac or pulmonary complications postoperatively (P0.2). Conclusions: The 2MWT was sensitive to change after cardiac surgery and showed moderate correlation with mea- sures of physical functioning in this population. However, the 2MWT could not identify those who developed complications in the postoperative period. Key Words: Cardiac surgery; Rehabilitation; Walking. © 2004 by the American Congress of Rehabilitation Medi- cine and the American Academy of Physical Medicine and Rehabilitation I N THE SURGICAL LITERATURE on postoperative inter- vention for management of cardiac patients, there is a lack of a standardized definition or measure of postoperative compli- cations. 1 With respect to postoperative pulmonary complica- tions, trials use a variety of outcomes such as chest radiographs and auscultation and a variety of clinical findings and pulmo- nary function tests. 1 None of the studies use a measure of functional capacity or activities of daily living (ADLs), al- though mobility and ability to carry out ADLs are reflective of complications and are strongly emphasized as the most impor- tant criteria used to determine readiness for discharge from rehabilitation in the immediate postoperative period. 2 How- ever, there is no objective measure of functional capacity that has been validated in the surgical population. Walk tests are measures that potentially could be adminis- tered as part of an assessment to determine functional perfor- mance, to monitor overall treatment effectiveness, and to assess readiness for discharge. 3 Originally, the 12-minute perfor- mance (run) test was developed as a guide to physical fitness in healthy young men. 4 This test was later modified to an indoor 12-minute walk test for the assessment of exercise tolerance in those with chronic bronchitis. 5 Shorter versions of this walk test, mainly the six- and two-minute walk tests (6MWT, 2MWT), were also developed in similar populations. 6 In these tests, patients are instructed to walk back and forth between 2 markers on a measured course, covering as much ground as possible in the allotted time period. The purpose of this study was to examine the construct validity and sensitivity (or responsiveness) of the 2MWT in patients who have had cardiac surgery. We chose to investigate this particular measure, because it is the most feasible and efficient measure of functional capacity. In addition, it may prove more clinically useful than the 6-minute version, because we have found that some patients are unable to ambulate more than 2 minutes (secondary to cardiac symptomatology). In addition, studies have shown this measure is comparable with the more well-established 6MWT. 6,7 We examined cross-sectional construct validity (convergent, known groups, discriminant) as well as sensitivity to change or responsiveness of the 2MWT. Sensitivity to change is the ability of a measure to assess change over time. 8 The sensitivity was examined by comparing the distance walked preopera- tively with the distance walked at discharge from hospital and on follow-up 6 to 8 weeks later. Construct validity is defined as “the degree to which a test behaves in accordance with hypoth- esis concerning how it should behave.” 8 Cross-sectional con- struct validity refers to the assessment of validity at 1 point in time, in this case preoperatively and then again at follow-up. There are 3 types of construct validity: convergent, known groups, and discriminant. 8 Convergent validity looks at the extent to which a measure agrees with the result of another measure. 8,9 In this study, we examined the correlation between the 2MWT and the Medical Outcomes Survey 36-Item Short- Form Health Questionnaire 10 (SF-36; physical functioning sub- scale) and Nottingham Extended Activity of Daily Living 11 From the Department of Physical Therapy, University of Toronto (Brooks, Parsons, Tran, Jeng, Gorczyca); Toronto Rehabilitation Institute (Parsons); University Health Network (Newton, Dear, Hawn); St. Michael’s Hospital (Lo); and Sunnybrook and Women’s College Health Sciences Centre (Silaj), Toronto, ON, Canada. Presented in part at the Better Breathing Conference, February 2002, Toronto, ON, Canada. Supported by the Conaught and Dean Fund, University of Toronto, the Canadian Physiotherapy Cardio-Respiratory Society, the Lung Association, and the Canadian Institute for Health Research. No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the author(s) or upon any organization with which the author(s) is/are associated. Reprint requests to Dina Brooks, PhD, Dept of Physical Therapy, RMI 848, 500 University Ave, Toronto, ON M5G 1V7, Canada, e-mail: dina.brooks@utoronto.ca. 0003-9993/04/8509-8771$30.00/0 doi:10.1016/j.apmr.2004.01.023 1525 Arch Phys Med Rehabil Vol 85, September 2004