Cox regression analysis, including sex, age, left ventricular ejection fraction, and New York Heart Association class, for calculation of risk of death at 6 months
| Cardiopulmonary variable | Risk ratio | 95% CI | p-value |
| V′O2,peak ≤14 mL·kg-1·min-1 | 2.9 | 1.5–5.4 | 0.002 |
| V′O2,peak ≤10 mL·kg-1·min-1 | 2.1 | 1.1–4.3 | 0.04 |
| V′O2,peak ≤50% normal | 2.0 | 1.1–3.7 | 0.03 |
| θL <11 mL·kg-1·min-1 | 2.7 | 1.3–5.6 | 0.007 |
| V′E–V′CO2slope >34 | 2.7 | 1.5–5.1 | 0.001 |
| V′O2,peak ≤14 + θL <11 mL·kg-1·min-1 | 3.2 | 1.5–6.7 | 0.003 |
| V′O2,peak ≤14 mL·kg-1·min-1+V′E–V′CO2 slope >34 | 4.5 | 2.1–10 | <0.001 |
| θL <11 mL·kg-1·min-1+V′E–V′CO2 slope >34 | 5.1 | 2.0–12.7 | 0.001 |
CI: confidence interval V′O2,peak: peak oxygen uptake; θL: lactate threshold; V′E–V′CO2 slope: slope of the increase in ventilatory equivalent for carbon dioxide. Reprinted from 138 with permission from the publisher.