Journal of Applied Physiology, Vol 72, Issue 5 1803-1809, Copyright © 1992 by American Physiological Society
Systematic nocturnal atrial demand pacing results in high-output heart failure
M. I. Talan, B. T. Engel and P. H. Chew
Laboratory of Behavioral Sciences, Gerontology Research Center, National Institute on Aging, National Institutes of Health, Baltimore, Maryland 21224.
Beat-to-beat parameters of heart rate (HR), intra-arterial blood pressure
(BP), central venous pressure, and derived indexes of cardiac output and
total peripheral resistance were recorded 18 h/day (from 1800 to 1200 h the
following day) in four monkeys (Macaca mulatta) during 20 control days
followed by 20 days of atrial demand pacing. The pacing rate was set at
approximately 10 beats/min above the fastest hourly average HR recorded
during the control period, i.e., sufficient to prevent the normal nocturnal
fall in HR. Nocturnal pacing resulted in progressive weekly increases in
central venous BP and arterial BP. Analyses of levels and diurnal trends in
hemodynamic parameters and cardiac function curves across consecutive 5-day
periods of nocturnal pacing revealed a hemodynamic pattern characteristic
of high-output heart failure, which progressively increased (week by week)
during the early morning hours (0500-0700). Sustained elevated left
ventricular work resulting from the prevention of a nocturnal fall in HR
may have been responsible for the reduction in cardiac function seen in
this experimental model.
