Applying current normative data to prognosis in heart failure: The Fitness Registry and the Importance of Exercise National Database (FRIEND)

Abstract

Introduction: Percent of predicted peak VO₂ (ppVO₂) is considered a standard measure for establishing disease severity, however, there are known limitations to traditional normative values. This study sought to compare ppVO₂ from the newly derived "Fitness Registry and the Importance of Exercise: a National Database" (FRIEND) registry equation to conventional prediction equations in a clinical cohort of patients undergoing cardiopulmonary exercise testing (CPX).

Methods and results: We selected 1094 patients referred for evaluation of heart failure (HF) symptoms who underwent CPX. ppVO₂ was calculated using the FRIEND, Wasserman/Hansen and Jones equations. Participants were followed for a median of 4.5 years [Interquartile range 3.5-6.0] for the composite endpoint of death, advanced HF therapy, or acute decompensated HF requiring hospital admission. Mean age was 48 ± 15 years and 62% were female. The FRIEND registry equation predicted the lowest ppVO₂ (measured/predicted; 71 ± 31%), compared to the Wasserman/Hansen (74 ± 29%) and Jones equations (83 ± 33%) (p < 0.001). All expressions of peak VO₂ were significant as univariate predictors of outcome with no significant differences between equations on pairwise analysis of receiver operating characteristic curves. When compared at a similar threshold of ppVO₂ the event rate was significantly lower in the FRIEND registry equation versus the currently used Wasserman and Jones equations.

Conclusion: The use of the newly derived FRIEND registry equation predicts HF outcomes; however, it appears to predict a higher predicted VO₂; the clinical implication being a lower threshold of percent predicted peak VO₂ should be considered when risk stratifying patients with HF.

Keywords: Cardiopulmonary exercise testing; Exercise capacity; Heart failure; Peak oxygen consumption.