Cardiovascular fitness and mortality after contemporary cardiac rehabilitation

Objective: To assess the association between cardiorespiratory fitness (CRF) and outcomes in a cardiac rehabilitation (CR) cohort.

Patients and methods: We conducted a retrospective study of 5641 patients (4282 men [76%] and 1359 women [24%]; mean ± SD age, 60.0±10.3 years) with coronary artery disease who participated in CR between July 1, 1996, and February 28, 2009. Based on peak metabolic equivalents (METs), patients were classified as low fitness (LFit) (<5 METs), moderate fitness (5-8 METs), or high fitness (>8 METs).

Results: Baseline fitness predicted long-term mortality: relative to the LFit group, patients with moderate fitness had an adjusted hazard ratio of 0.54 (95% CI, 0.42-0.69), and those with high fitness a hazard ratio of 0.32 (95% CI, 0.24-0.44). Improvement in CRF at 12 weeks was associated with decreased overall mortality, with a 13% point reduction with each MET increase (P<.001) and a 30% point reduction in those who started with LFit. At 1 year, each MET increase in CRF was associated with a 25% point reduction in overall mortality in the whole group (P<.001).

Conclusion: In this study of contemporary CR patients, higher baseline fitness predicted lower mortality. The novel finding was that improvement in fitness during a CR program and improvements that persisted at 1 year were also associated with decreased mortality, most strongly in patients who start with LFit.