Prognostic impact of the addition of peak oxygen consumption to the Seattle Heart Failure Model in a transplant referral population

Abstract

Background: In this study we investigated whether the addition of peak oxygen consumption (VO2) improves the predictive accuracy of the Seattle Heart Failure Model (SHFM). The SHFM is a validated multivariate risk model that uses NYHA classification to assess functional capacity rather than peak oxygen consumption (VO2). Methods: Outpatients (n = 1,240) evaluated for transplant at three centers had their SHFM score calculated and peak VO2 measured. The outcomes assessed were death/LVAD/urgent transplant with censoring at the time of elective transplant. Results: Over the course of 4.0 (mean) years of observation, there were 571 events. Both the SHFM score (χ2 = 227) and peak VO2 (χ2 = 88, both p < 0.0001) were highly predictive of outcomes. The SHFM and peak VO2 were modestly correlated (r = 0.39, p < 0.0001). In a multivariate Cox model, peak VO2 added to the SHFM with a hazard ratio of 0.949 (p < 0.0001) for each 1-ml/kg/min increase. Peak VO 2 improved both the net reclassification improvement and integrated discrimination index (both p ≤ 0.0002). Peak VO2 provided additive prognostic information within each SHFM score (p < 0.05). The 1-year areas under the receiver-operating characteristic curve were obtained for peak VO 2 (0.645, 95% CI 0.606 to 0.684), SHFM (0.758, 95% CI 0.721 to 0.795) and SHFM with peak VO2 (0.766, 95% CI 0.731 to 0.802). The SHFM-predicted vs actual survival free of LVAD/UNOS Status 1 transplant at 1 year (86% vs 83%) and 4 years (63% vs 63%) were similar. Conclusions: The multivariate SHFM is a powerful predictor of death/LVAD/urgent transplant. Peak VO2 adds prognostic information across the spectrum of the SHFM, but changes in decision regarding transplant listing occur mainly in moderate-risk patients. © 2012 International Society for Heart and Lung Transplantation.