Background In patients with chronic coronary syndromes (CCS) increased ventilation/carbon dioxide production (VE/VCO2) slope has been found to predict disease progression and mortality similarly to patients with heart failure (HF), however, chemosensitivity has rarely been assessed in patients with CCS. Method Patients with CCS, HF with reduced ejection fraction (EF<50%), old healthy (45+ years) and young adult healthy controls (<35 years) were recruited. For patients, a VE/VCO2 slope ≥36 was an inclusion criterion. The Duffin rebreathing method was used to determine the resting end-expiratory partial pressure of carbon dioxide (PETCO2), ventilatory recruitment threshold (VRT) and slope (sensitivity) during a hyperoxic (150 mmHg O2) and hypoxic (50 mmHg O2) rebreathing test to determine central and peripheral chemosensitivity. Results In patients with CCS, HF, and old and young controls, median VE/VCO2 slopes were 40.2, 41.3, 30.5 and 28.0, respectively. Both patient groups had similarly reduced hyperoxic VRT (at PETCO2 42.1 and 43.2 mmHg) compared to 46.0 and 48.8 mmHg in the old and young controls. Neither hypoxic VRT nor hyper- or hypoxic slopes were significantly different in patients compared to controls. Both patient groups had lower resting PETCO2 than controls, but only patients with HF had increased breathing frequency and rapid shallow breathing at rest. Conclusion In patients with cardiac disease and excess ventilation, central chemoreflex VRT was reduced independently of the presence of heart failure. Low VRTs were related to resting excess ventilation in patients with CCS or HF, however, rapid shallow breathing was present only in patients with HF.

The authors have declared no competing interest.

NCT05057884

There was no funding for the present study.

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