An oscillation of the respiratory control system accounts for most of the heart period variability of chronic heart failure patients.

Abstract

A periodic breathing (PB) pattern is often observed in chronic heart failure (CHF) patients (pts). In order to clarify the role of this abnormal respiratory activity upon heart period variability we investigated, in a group of 20 stable CHF pts (NYHA class II to III, median EF 24%) showing a PB pattern, 1) whether observed data were consistent with the instability hypothesis of PB and 2) the relationship between oscillations of heart period and the contemporary fluctuations of ventilatory and chemoreceptor activity. Univariate and bivariate spectral analysis were performed on short-term resting recordings of instantaneous lung volume (ILV), instantaneous minute ventilation (IMV), heart period (HP) and arterial O2 saturation at the ear (SpO2). A very low frequency (VLF) oscillation around 0.02 Hz, associated with PB, was observed in all signals and contributed to 75% (23 divided by .99) (median (range)) of the HP variability. The coherence between ILV and HP was 0.77 (0.3 divided by 0.95) and between SpO2 and HP 0.8 (0.4 divided by 0.98. A high coherence was also found between IMV and SpO2: 0.9 (0.6 divided by 0.98). The median phase lag between IMB and SpO2 was -211 degrees (-240 divided by -156), between ILV and HP -205 degrees (-260 divided by -180) and between SpO2 and HP 0 degree (-26 divided by 30). The estimated lung-to-ear circulation time was 24.5 s (12.5 divided by 36.5). This study definitely confirms that during PB a common rhythm is shared between the respiratory and cardiovascular regulatory system Taking into account the error introduced by the measuring process, our results, are consistent with the hypothesis that periodic breathing of CHF pts originates from an instability of the feedback control system of ventilation. Hence most of the HP variability of these pts simply reflects abnormal pattern of respiratory activity.