Arterial blood pressure and heart period relationships during periodic breathing in chronic heart failure patients

Periodic breathing (PB) is highly prevalent (>60%) in awake chronic heart failure (CHF) patients with moderate to severe symptoms and poor ventricular function. In this study, the authors analyzed by spectral techniques the variability of systolic (SAP) and diastolic (DAP) arterial pressure and their relationship with the variability of the heart period (HP) in 20 resting CHF patients with stable PB. The relationship between instantaneous lung volume (ILV) and SAP and the association between the phase shift SAP-HP and baroreflex sensitivity (BRS) were also investigated. All signals showed a narrowband very low frequency (VLF) component about 0.02 Hz (the frequency of PB) which explained 38% (22) (median (quartile range)) of ILV variance, 74% (33) of HP, 86% (15) of SAP and 72% (21) of DAP. The coherence and phase at the VLF peak were 0.76 (0.2) and -56/spl deg/ (41) for ILV-SAP, 0.71 (0.2) and -149/spl deg/ (52) for SAP-HP and 0.77 (0.3) and -191/spl deg/ (38) for DAP-HP. The correlation coefficient between the phase shift SAP- HP and BRS at the VLF peak was 0.78 (p<0.001). This study demonstrates that during PB in CHF, both the respiratory and cardiovascular control systems are entrained by the same VLF rhythm which explains most of the variability of cardiovascular parameters. The VLF oscillation of SAP follows the corresponding oscillation of HP but they change in the opposite direction. The shift depends on the functioning of the baroreflex.