• Jonathan Myers, Pradeep Gujja, Suresh Neelagaru, Leon Hsu, Timothy Vittorio, Tamika Jackson-Nelson, and Daniel Burkhoff.
• Cardiology Division, Veterans Affairs Palo Alto Health Care System, Stanford University, Palo Alto, CA 94304, USA. drj993@aol.com
• Med Sci Sports Exerc. 2009 Jan 1;41(1):19-25.

IntroductionIn patients with heart failure (HF), end-tidal CO2 pressure (PetCO2) is related to ventricular function at rest and has been shown to predict prognosis. However, little is known about the association between ventricular performance and PetCO2 responses to exercise.MethodsForty-eight patients with HF and 13 normal subjects underwent cardiopulmonary exercise testing (CPX), while cardiac output and other hemodynamic measurements at rest and during exercise were obtained using a novel, noninvasive, bioreactance device based on assessment of relative phase shifts of electric currents injected across the thorax, heart rate, and ventricular ejection time. CPX responses and indices of cardiac performance were compared between normal subjects and HF patients achieving above and below a PetCO2 of 36 mm Hg at the ventilatory threshold (PetCO2@VT).ResultsHF patients with an abnormal PetCO2@VT (<36 mm Hg) had a lower exercise capacity, a lower .VO2@VT, a higher .V_E/.VCO2 slope, and lower oxygen uptake efficiency slope (OUES) values compared with normal subjects and patients achieving a normal PetCO2@VT. Patients with reduced PetCO2@VT had lower peak cardiac output responses to exercise (20.0 +/- 10, 17.8 +/- 6, and 13.7 +/- 7 L x min for normal subjects and HF patients with normal and abnormal PetCO2 responses to exercise, respectively, P = 0.04). PetCO2@VT was inversely related to the .V_E/.VCO2 slope (r = -0.78, P < 0.001) and directly related to the OUES (r = 0.55, P < 0.001).ConclusionReduced PetCO2 reflects impairments in the functional, ventilatory, and cardiac performance response to exercise in patients with HF. PetCO2 can supplement other clinical and CPX indices in the functional and prognostic evaluation of patients with HF.

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