Background: Cardiopulmonary exercise testing (CPET) variables provide valuable prognostic information in the heart failure (HF) population. The purpose of the present study is to assess the ability of resting end-tidal carbon dioxide partial pressure (PETCO2) to predict cardiac-related events in patients with HF.
Methods: 121 subjects diagnosed with compensated HF underwent CPET on an outpatient basis. Mean age and ejection fraction were 49.3 years (+/-14.7) and 28.4% (+/-13.4), respectively. Resting P(ET)CO2 was determined immediately prior to the exercise test in the seated position. Peak oxygen consumption (VO2) and the minute ventilation-carbon dioxide production (VE/VCO2) slope were also acquired during CPET.
Results: There were 41 cardiac-related hospitalizations and 9 cardiac-related deaths in the year following CPET. Mean resting P(ET)CO2, peak VO2 and VE/VCO2 slope were 34.1 mmHg (+/-4.6), 14.5 ml*kg(-1)*min(-1) (+/-5.1) and 35.9 (+/-8.7) respectively. Univariate Cox regression analysis revealed that resting P(ET)CO2 (Chi-square=28.4, p<0.001), peak VO2 (Chi-square=21.6, p<0.001) and VE/VCO2 slope (Chi-square=54.9, p<0.001) were all significant predictors of cardiac related events. Multivariate Cox regression analysis revealed resting P(ET)CO2 added to the prognostic value of VE/VCO2 slope in predicting cardiac related events (residual Chi-square=4.4, p=0.04). Peak VO2 did not add additional value and was removed (residual Chi-square=3.2, p=0.08).
Conclusions: These results indicate a resting ventilatory expired gas variable possesses prognostic value independently and in combination with an established prognostic marker from the CPET. Resting P(ET)CO2 may therefore be a valuable objective measure to obtain during both non-exercise and exercise evaluations in patients with HF.