Aims: We studied the prognostic significance of the ventilatory equivalent of carbon dioxide production (VEqCO(2)) at different time-points of a maximal cardiopulmonary exercise test (CPET) in patients with suspected heart failure (HF).
Methods and results: The VEqCO(2) was calculated at three different time-points; VEqCO(2) (rest) was calculated following 30 s of resting data immediately prior to the start of exercise; VEqCO(2) (nadir) was the lowest 30-s average over the duration of the test; VEqCO(2) (peak) was calculated using the mean value of the final 30 s of exercise. We included a healthy control group who had no evidence of cardiorespiratory disease. Four hundred and twenty-three patients with suspected HF (mean age 63 ± 12 years; 80% males; left ventricular ejection fraction 36 ± 6 %; peak oxygen uptake 22.3 ± 8.1 mL kg(-1) min(-1); VE/VCO(2) slope 34 ± 8) were included in the study. Seventy-eight healthy participants (62% males; age 61 ± 11 years) were recruited as controls. One hundred and eighteen patients died during follow-up with a median follow-up of 8.6 ± 2.1 years in survivors. The strongest univariable predictors of all-cause mortality were VEqCO(2) (nadir) (χ(2) = 47.9), peak oxygen uptake (χ(2) = 53.0), and the VE/VCO(2) slope (χ(2) = 31.7). In a Cox multivariable proportional hazards model, VEqCO(2) (nadir) (χ(2) = 8.8), peak systolic blood pressure (χ(2) = 6.0), and age (χ(2) = 6.6) were the most potent independent predictors of all-cause mortality.
Conclusion: The VEqCO(2) (nadir) provides greater prognostic value than other related ventilatory variables in patients with suspected HF. Further work in other populations is required to confirm our conclusions.