Popovic D, et al. - Researchers tested their premise that a flattening oxygen consumption (VO₂) trajectory is helpful in phenotyping disease severity and prognosis in heart failure (HF) with either reduced (HFrEF), mid-range (HFmrEF) or preserved (HFpEF) ejection fraction. A flattening VO₂ trajectory was found to be a probable novel and robust predictor of events in HF with any ejection fraction. This oxygen pattern might suggest a real-time decrease in pulmonary blood flow to the left heart, given the association of right-sided cardiac dysfunction with pulmonary hypertension.

Methods

• This study included 319 HF patients (198 HFrEF, 80 HFmrEF, and 41 HFpEF) who underwent CPET.
• A flattening VO₂ trajectory was tracked and defined as an inflection of VO₂ linearity as a function of work rate with a second slope downward inflection >35% extent of the first one.
• Researchers determined peak VO₂, the minute ventilation/carbon dioxide production (VE/VCO₂) slope, and the presence of exercise oscillatory ventilation (EOV).
• Echocardiography was used to measure pulmonary artery systolic pressure (PASP) and tricuspid annular plane systolic excursion (TAPSE).
• The combination of all-cause death, heart transplantation and left ventricular assist device implantation was primary outcome, and secondary outcome included primary outcome, plus hospitalization for cardiac reasons.

Results

• In 92 patients (28.8%), the occurrence of a flattening VO₂ was detected.
• At rest, significantly higher PASP and significantly lower TAPSE were detected (P < 0.001).
• Data showed that, in the multivariate model including peak VO₂, VE/VCO₂ slope, EOV and VO₂ trajectory, a flattening VO₂ trajectory and EOV were retained in the regression for primary (X² = 35.78, and 36.36, respectively; P < 0.001) and secondary (X² = 12.45 and 47.91, respectively; P < 0.001) outcomes.