ARE CHANGE IN METS DURING CARDIAC REHAB RELATED TO CHANGE IN PEAK VO2 AND 6MWD?

Abstract

BACKGROUND Change in metabolic equivalents of task (METs) during exercise training is often used as a program outcome in cardiac rehabilitation (CR). The purpose of this study is to assess the correlation between the change in estimated exercise training METs during a CR program and the change in six-minute walk distance (6MWD) and change in peak oxygen uptake (VO2). METHODS This is a secondary analysis of data from the iATTEND trial- a randomized controlled trial that compared facility based CR versus hybrid CR. Subjects included in this analysis had a history of myocardial infraction, coronary revascularization, heart failure, or valve surgery and completed ≥12 sessions of CR. METs during exercise training were estimated using ACSM treadmill equations from the average of the second, third and fourth sessions of CR and the final three sessions of CR. 6MWD and peak VO2 was derived from a symptom limited graded exercise treadmill test with gas exchange were collected at baseline before starting CR and within 14 days of completing CR. Pearson correlation coefficient was determined between change in estimated exercise training METs and both change in 6MWD and in peak VO2. RESULTS The final cohort was n=237 (age=59±12 years; 35% women; 57% non-white race). The correlation between change in estimated exercise training METs and 6MWD was r=0.257, r=0.245, and r=0.235 among patients who completed ≥12 sessions of CR, ≥24 sessions of CR, and 36 sessions of CR, respectively. The correlation between change in estimated exercise training METs and peak VO2 was r=0.121, r=0.100, and r=0.136 among patients who completed ≥12 sessions of CR, ≥24 sessions of CR, and 36 sessions of CR, respectively. CONCLUSIONS Although change in estimated exercise training METs during a CR program, change in 6MWD, and change in peak VO2 have each been used to describe change in exercise tolerance for program outcomes, the association between these variables is low (r= <0.3). This finding was independent regardless of the number of sessions completed. Further research is needed to better understand the relationship between the various methods of assessing change in exercise tolerance and program outcomes in CR.