Cardiorespiratory Coupling and Exercise Capacity in Patients with Chronic Heart Failure

Cardiopulmonary exercise testing (CPET) is crucial for assessing exercise capacity in chronic heart failure (CHF) patients, with peak oxygen consumption (VO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> peak) being the gold standard for cardiorespiratory fitness. This study explores the correlation between VO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> peak and cardiorespiratory coupling (CRC). The CRC was calculated via the power of heart period (HP) variability in the high frequency (HF, from 0.15 to 0.4 Hz) band expressed in absolute units ($\mathrm{HFa}_{\mathbf{H}}$) and the squared coherence ($\mathrm{K}^{2}$) between HP variability and respiration (RESP) in the HF band ($\mathrm{K}^{\mathbf{2}} \mathrm{HF}$). We computed the difference between CRC markers measured after CPET with respect to those before CPET in 25 CHF patients (age: $62 \pm 9 \mathrm{yrs}$, NYHA class: I to III, 15 males). A positive correlation between variation of CRC markers and VO2 peak ($r=0.5$; $p=$ 0.007) was observed. No correlation was found between HF<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">aHP</inf> and VO2peak. The findings suggest CRC analysis as a supplementary method for evaluating exercise capacity in CHF patients, providing insights beyond traditional measures.