There is limited understanding on the potential differences in the pathophysiology between de novo heart failure with reduced ejection fraction (HFrEF) and acute on chronic HFrEF. The aim of this study was to assess differences in cardiorespiratory fitness (CRF) parameters between de novo heart failure and acute on chronic HFrEF using cardiopulmonary exercise testing (CPX). We retrospectively analyzed CPX data measured within 2 weeks of discharge following acute hospitalization for HFrEF. Data are reported as median and interquartile range or frequency and percentage (%). We included 102 patients: 32 (31%) women, 81 (79%) black, 57 (51 to 64) years of age, BMI of 34 (29 to 39) Kg/m2. Of these, 26 (25%) had de novo HFrEF and 76 (75%) had acute on chronic HFrEF. When compared with acute on chronic, patients with de novo HFrEF had a significantly higher peak oxygen consumption (VO2) (16.5 [12.2 to 19.4] vs 12.8 [10.1 to 15.3] ml·kg-1·min-1, p <0.001), %-predicted peak VO2 (58% [51 to 75] vs 49% [42 to 59]) p = 0.012), peak heart rate (134 [117 to 147] vs 117 [104 to 136] beats/min, p = 0.004), peak oxygen pulse (12.2 [10.5 to 15.5] vs 9.9 [8.0 to 13.1] ml/beat, p = 0.022) and circulatory power (2,823 [1,973 to 3,299] vs 1,902 [1,372 to 2,512] mm Hg·ml·kg-1·min-1, p = 0.002). No significant difference in resting left ventricular ejection fraction was found between groups. In conclusion, patients with de novo HFrEF have better CRF parameters than those with acute on chronic HFrEF. These differences are not explained by resting left ventricular systolic function but may be related to greater preservation in cardiac reserve during exercise in de novo HFrEF patients.
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