AJP - Heart and Circulatory Physiology, Vol 243, Issue 6 990-H997, Copyright © 1982 by American Physiological Society
Postextrasystolic potentiation and contractile reserve: requirements and restrictions
R. M. Lust, L. O. Lutherer, M. E. Gardner and M. W. Cooper
These studies were conducted to examine the basic characteristics of
postextrasystolic potentiation (PESP) and the relationship of loading
effects to PESP. Measurements of left ventricular (LV) and aortic
pressures, the rate of pressure rise, and echocardiographically determined
LV dimensions were made in anesthetized open-chest dogs. The hearts were
paced, and timed extrasystoles were introduced that were followed by
postextrasystoles (PES). PES's were elicited after an interval equal to
either a full compensatory pause or a time when the diastolic properties of
the LV could not be distinguished from control (isolength). Potentiation of
contraction for the PES's introduced after an isolength pause was dependent
on both the heart rate and the extrasystolic interval, whereas the PES's
that occurred after a full pause showed no dependence on either of these
intervals. PESP elicited during the isolength period was not dependent on
either preload and afterload. It is concluded that PESP depends on the
combination of heart rate and extrasystolic and postextrasystolic
intervals. Further, PESP may be inaccurate in assessing contractile reserve
unless the heart rate and extrasystolic interval are known and the PES is
introduced after an isolength pause.
