Introduction: Cardiac rehabilitation (CR) in stable coronary heart disease (CHD) has been shown to improve mortality commensurate with levels of improvement in cardiorespiratory fitness (CRF) and lean mass. The current study examines the effects of changes in LM in determining mortality outcomes after CR.
Hypothesis: Effects of weight changes on mortality are influenced by the obesity paradox; stratifying weight changes by lean mass (LM) will help differentiate healthy from unhealthy weight loss.
Methods: 1110 subjects with stable CHD referred for CR between 01/2000 and 06/2013 with a mean follow-up of 6.3 years were stratified according to median change in peak oxygen consumption (VO2) measured during maximal cardiopulmonary exercise testing and median change in LM index (LMI). Mortality differences were adjusted for age, sex, baseline VO2, ejection fraction, and body mass index.
Results: Changes in weight following CR were not a significant predictor of mortality. Likewise, changes in waist circumference and LMI were not significant independent predictors of mortality. However, change in LMI when combined with change in peak VO2 yielded significant prognostic information between those in the top and bottom 50th percentile of peak VO2 changes (HR 2.58; 95% CI 1.54-4.33; p < 0.001) and a strong trend toward significance for lower mortality in individuals who gain LMI (HR 1.72; 95% CI 0.99-2.97; p = 0.05). (Figure 1)
Conclusions: In patients with CHD, stratifying changes in LM by peak VO2 has the potential to gauge the response to exercise training and associated mortality benefits than each measure alone. Further study is needed to determine if targeting both increases in VO2 and LMI can lead to better outcomes in patients enrolling into CR.