Introduction:
Several patients with coronary heart disease (CHD) present reduced survival despite completing cardiac rehabilitation (CR), suggesting that the level of cardiorespiratory fitness (CRF) achieved might remain suboptimal. The purposes of this study were: 1) to examine the independent association of peak oxygen consumption (VO
2
), a measure of CRF, at post-CR with long-term survival; and 2) to establish an optimal cut-off for peak VO
2
at post-CR that best predicts mortality risk.
Methods:
853 patients with CHD (mean age of 64±10 years old) who were referred to CR between January 1, 2000, and June 30, 2013, at Ochsner Medical Center were analyzed for this study. We measured pre- and post-CR peak VO
2
. Mortality data were collected using National Death Index. Cox proportional hazard regression model was used to examine the risk of all-cause mortality associated with peak VO
2
at post-CR, independent of peak VO
2
at pre-CR and related changes during CR. Contal and O’Quigley’s method were used to determine the optimal cut-off for peak VO
2
at post-CR based on a split-sample approach.
Results:
Mean peak VO
2
at post-CR was 21.01±6.25 mL/kg/min (75% and 51% predicted peak VO2 using Wasserman and FRIEND Registry equations, respectively). During a mean follow-up of 6.55 years, 106 subjects (12.4%) died. Peak VO
2
at post-CR independently predicted mortality (Hazard Ratio: 0.82 [0.77-0.87], p<0.001). We identified peak VO
2
of ≥17.6 kg/mL/min as optimal cut-off best predicting survival (
Figure 1, Panel A
) and the %predicted peak VO2 at post-CR ≥62.1% using Wasserman (
Figure 1, Panel B
) and ≥41.4% using FRIEND Registry (
Figure 1, Panel C
) as the alternative optimal cut-offs.
Conclusions:
In patients with CHD undergoing CR, post-CR peak VO
2
independently predicts long-term survival. These results suggest that patients with CHD presenting a peak VO
2
lower than the cut-off identified herein may benefit from additional sessions of CR or higher intensity exercise training.
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