Pathophysiological interactions between respiration, posture and the cardiovascular system during sleep in patients with heart failure.
Published: 2004
Language: eng
Number of pages: 208
Description: In summary, there exist significant interactions in human CHF between sleep and the cardiovascular system, mediated in part through CSR-CSA and sleeping posture. It is speculated that the rhythmic oscillations in autonomic tone brought about by CSR-CSA may ultimately contribute to the sympatho-excitation and increased mortality long observed in patients with CHF and CSR-CSA. Conversely, avoidance of the LLD position may be a self-protective mechanism by which these patients attenuate hemodynamic or autonomic compromise.The conceptual model of congestive heart failure (CHF) has evolved over the last two decades to emphasize over-activity of the autonomic nervous system as one of its cardinal features. However, little attention has been paid to the potential for excitation or inhibition of the autonomic nervous system in patients with CHF by phenomena that are exclusive to sleep. This dissertation explores two such phenomena: (1) Cheyne-Stokes respiration with central sleep apnea (CSR-CSA), a sleep-related breathing disorder, and (2) sleeping posture.Patients with CHF were found to spend significantly less time sleeping in the left lateral decubitus (LLD) position than in the right lateral decubitus position. Avoidance of the LLD position was correlated with the severity of heart failure: less time was spent sleeping on the left side by those with larger hearts, higher cardiac filling pressures and lower cardiac output.To test the hypothesis that CSR-CSA exerts acute effects on the autonomic nervous system, its effects on a number of cardiovascular phenomena, including heart rate, blood pressure, atrioventricular (AV) conduction, and ventricular ectopy were investigated. During CSR-CSA, heart rate and blood pressure oscillated in association with respiratory oscillations. In patients with atrial fibrillation, ventricular rate again oscillated in association with CSR-CSA despite the absence of normal respiratory arrhythmia. Comparison of RR-intervals during CSR-CSA indicated that this breathing disorder exerts this effect on ventricular rate by inducing cyclical changes in AV conduction properties. Ventricular premature beats (VPBs) were found to occur more frequently during the hyperpneic phase than the apneic phase of CSR-CSA. VPB frequency was also found to be higher during periods of CSR-CSA than during periods of regular breathing.
Notes: Adviser: T. Douglas Bradley.

Thesis (Ph.D.)--University of Toronto, 2004.

Electronic version licensed for access by U. of T. users.

Source: Dissertation Abstracts International, Volume: 65-05, Section: B, page: 2337.