Very low frequency oscillations of heart period: relationship to respiratory activity and blood pressure in heart failure patients

The authors have analyzed the spectral content of the very low frequency band (VLF, 0.01-0.04 Hz) of contemporary short-term recordings of heart period (HP), systolic arterial pressure (SAP), instantaneous lung volume (ILV) and instantaneous tidal volume (ITV) from 16 moderate congestive heart failure (CHF) patients not showing Cheyne-Stokes (C-S) respiration. A well-defined peak around 0.02 Hz was detected in the considered signals in most of the patients analyzed. The majority of patients also showed moderate (>0.5) to high (>0.8) coherence in the region of the VLF peak between HP and SAP and between these signals and the respiratory ones. Since the VLF oscillation of the respiratory signals can be explained as a mild form of periodic breathing, due to the instability of the respiratory control system, the authors' data support the hypothesis that this rhythm is transmitted to the cardiovascular control system through substantially linear mechanical and neural couplings, generating the VLF oscillation of HP and SAP.<
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