Anaerobic threshold and respiratory compensation point identification during CPET in chronic heart failure
Background. We evaluated the prognostic significance of the simple presence or absence of identifiable anaerobic threshold (AT) and respiratory compensation point (RCP) at cardiopulmonary exercise test (CPET) performed with a maximal incremental exercise protocol. Methods. In the present multicenter study, we retrospectively analyzed data of 1995 reduced-ejection-fraction heart failure (HFrEF) patients. All underwent clinical and laboratory evaluation, echocardiography, and maximal CPET at baseline. The analysis was performed according to absence of identified AT and RCP (group 1, n=292, 15%), presence of AT but absence of identified RCP (group 2, n=920, 46%), and presence of both AT and RCP (group 3, n=783, 39%). The study endpoint was the composite of cardiovascular mortality/urgent heart transplantation/left ventricular assist device implantation. Results. Median follow-up was 2.97 years (interquartile range 1.50–5.35 years). Eighty-seven (30%), 169 (18%), and 111 (14%) events were observed in group 1, 2, and 3, respectively (p= 0.025). Compared to group 3 (best survival patients), the likelihood of reaching the study endpoint increased 2.7 times when neither AT nor RCP were identified (HR 2.74), and 1.4 times when only AT was identified (HR=1.39). Moreover, adding the presence/absence of identified AT and RCP improved peak VO2 prognostic power, since a significant reclassification was obtained (3.57%, 95% CI 1.9%, 5.2%, p <0.001). Conclusion. AT and RCP identification has a potential role in the prognostic stratification of HFrEF.