Authors

1. Ritt, Luiz Eduardo MD
2. Oliveira, Ricardo Brandao PhD
3. Myers, Jonathan PhD
4. Arena, Ross PhD
5. Peberdy, Mary Ann MD
6. Bensimhon, Daniel MD
7. Chase, Paul Med
8. Forman, Daniel MD
9. Guazzi, Marco MD, PhD

Abstract

PURPOSE: While patients with heart failure who achieve a peak oxygen uptake (peak

O₂) of 10 mL[middle dot]kg^-1[middle dot]min^-1 or less are often considered for intensive surveillance or intervention, those achieving 14 mL[middle dot]kg^-1[middle dot]min^-1 or more are generally considered to be at lower risk. Among patients in the "intermediate" range of 10.1 to 13.9 mL[middle dot]kg^-1[middle dot]min^-1, optimally stratifying risk remains a challenge.

METHODS: Patients with heart failure (N = 1167) referred for cardiopulmonary exercise testing were observed for 21 +/- 13 months. Patients were classified into 3 groups of peak

o₂ (<=10, 10.1-13.9, and >=14 mL[middle dot]kg^-1[middle dot]min^-1). The ability of heart rate recovery at 1 minute (HRR₁) and the minute ventilation/carbon dioxide output (

E/

co₂) slope to complement peak

o₂ in predicting cardiovascular mortality were determined.

RESULTS: Peak

o₂, HRR₁ (<16 beats per minute), and the

E/

co₂ slope (>34) were independent predictors of mortality (hazard ratio 1.6, 95% CI: 1.2-2.29, P = .006; hazard ratio 1.7, 95% CI: 1.1-2.5, P = .008; and hazard ratio 2.4, 95% CI: 1.6-3.4, P < .001, respectively). Compared with those achieving a peak

o₂ >= 14 mL[middle dot]kg^-1[middle dot]min^-1, patients within the intermediate range with either an abnormal

E/

co₂ slope or HRR₁ had a nearly 2-fold higher risk of cardiac mortality. Those with both an abnormal HRR₁ and

E/

co₂ slope had a higher mortality risk than those with a peak

o₂ <= 10 mL[middle dot]kg^-1[middle dot]min^-1. Survival was not different between those with a peak

o₂ <= 10 mL[middle dot]kg^-1[middle dot]min^-1 and those in the intermediate range with either an abnormal HRR₁ or

E/

co₂ slope.

CONCLUSIONS: HRR₁ and the

E/

co₂ slope effectively stratify patients with peak

o₂ within the intermediate range into distinct groups at high and low risk.