Improved percent-predicted peak VO2 is associated with lower risk of hospitalization in patients with coronary heart disease. Analysis from the FRIEND registry

Background: Normal standards for peak oxygen consumption (VO2peak) are controversial because they tend to be population and protocol specific. This study was undertaken to examine the association between percentage of age-predicted VO2peak and all-cause hospital readmission in cardiac outpatients who were referred to an exercise-based secondary prevention program. Methods: Hospital readmission was assessed in 1283 male patients with coronary heart disease (CHD) three years after enrolment, and related to the age-predicted VO2peak derived from the Fitness Registry and the Importance of Exercise: A National Data Base equation (FRIEND%PRED). VO2peak was estimated using a moderate perceptually regulated 1-km treadmill-walking test. Readmission was also assessed during the fourth-to-sixth years as function of improvement in FRIEND%PRED in 845 patients who were re-evaluated 3 years after baseline. Results: During the 3-years after baseline, readmission rate was lower across increasing tertiles of FRIEND%PRED. Compared to the lowest tertile, the adjusted hazard ratios (HRs) for the second and third tertile were 0.98 (95% CI 0.76–1.27, p = 0.90) and 0.71 (0.53–0.95, p = 0.002). The rate of readmission from the fourth-to-sixth years after baseline was lower across tertiles of improved FRIEND%PRED, with adjusted HRs 0.78 (0.60–1.03, p = 0.08) and 0.58 (0.42–0.75, p < 0.0001) for the intermediate and high tertiles vs the lowest tertile. After adjustment for confounders, every 1 unit % increase in FRIEND%PRED was associated with a 3% reduction in risk of readmission (HR 0.97, 0.95–0.98, p < 0.0001). Conclusions: Age-predicted VO2peak estimated by a moderate treadmill-walk predicts hospital readmission in outpatients with CHD undergoing secondary prevention.