Long-Term Maintenance of Cardiorespiratory Fitness Gains After Cardiac Rehabilitation Reduces Mortality Risk in Patients With Multimorbidity

Purpose:The objective of this study was to characterize the impact of multimorbidity and cardiorespiratory fitness (CRF) on mortality in patients completing cardiac rehabilitation (CR). Methods:This cohort study included data from patients with a history of cardiovascular disease (CVD) completing a 12-wk CR program between January 1996 and March 2016, with follow-up through March 2017. Patients were stratified by the presence of multimorbidity, which was defined as having a diagnosis of >= 2 noncommunicable diseases (NCDs). Cox regression analyses were used to evaluate the effects of multimorbidity and CRF on mortality in patients completing CR. Symptom-limited exercise tests were completed at baseline, immediately following CR (12 wk), with a subgroup completing another test at 1-yr follow-up. Peak metabolic equivalents (METs) were determined from treadmill speed and grade. Results:Of the 8320 patients (61 +/- 10 yr, 82% male) included in the analyses, 5713 (69%) patients only had CVD diagnosis, 2232 (27%) had CVD+1 NCD, and 375 (4%) had CVD+>= 2 NCDs. Peak METs at baseline (7.8 +/- 2.0, 6.9 +/- 2.0, 6.1 +/- 1.9 METs), change in peak METs immediately following CR (0.98 +/- 0.98, 0.83 +/- 0.95, 0.76 +/- 0.95 METs), and change in peak METs 1 yr after CR (0.98 +/- 1.27, 0.75 +/- 1.17, 0.36 +/- 1.24 METs) were different (P < .001) among the subgroups. Peak METs at 12 wk and the presence of coexisting conditions were each predictors (P < .001) of mortality. Improvements in CRF by >= 0.5 METS from baseline to 1-yr follow-up among patients with or without multimorbidity were associated with lower mortality rates. Conclusion:Increasing CRF by >= 0.5 METs improves survival regardless of multimorbidity status.