AJP - Regulatory, Integrative and Comparative Physiology, Vol 264, Issue 1 186-R196, Copyright © 1993 by American Physiological Society
Primary coronary vasodilation associated with pauses in heart rhythm during sleep
L. W. Dickerson, A. H. Huang, B. D. Nearing and R. L. Verrier
Department of Pharmacology, Georgetown University School of Medicine, Washington, District of Columbia 20007.
We observed 162 episodes of pause in heart rhythm in chronically
instrumented dogs primarily during transitions from deep slow-wave sleep to
other stages of sleep. These pauses lasted 1.1-8.0 s and were followed by
increases in coronary blood flow (CBF) averaging 30% and ranging up to 84%.
The postpause surges in CBF do not appear to be mediated by local metabolic
factors because the flow surges occurred without significant changes in the
heart rate x systolic blood pressure (HRxSBP) product, a standard index of
cardiac metabolic activity. Enhanced vagal tone is suggested by the
background of marked respiratory sinus arrhythmia, low average heart rates,
and the hallmark event, the pause in heart rhythm. In a series of
experiments in alpha-chloralose-anesthetized dogs, we demonstrated that
direct vagus nerve stimulation can induce both the pause in heart rhythm
and the postpause increase in CBF in a pattern similar to that observed
during sleep. This response was markedly attenuated after pericoronary
denervation. These observations provide suggestive evidence but not
definitive proof that enhanced vagal activity may be involved in the
increase in CBF after spontaneous pauses in heart rhythm during sleep.
