AJP - Heart and Circulatory Physiology, Vol 253, Issue 6 1506-H1513, Copyright © 1987 by American Physiological Society
Modification of force-interval relations during early adaptation to pressure overload in dogs
B. Crozatier, L. Hittinger and M. Chavance
INSERM U2, Hopital Leon Bernard, Limeil-Brevannes, France.
Ventricular function was analyzed in the end-systolic and end-ejection
pressure-volume diagrams in seven conscious dogs during acute aortic
stenosis (AS) and sustained stenosis (SS) 24 h later. Dogs were previously
instrumented with a left ventricular micromanometer and ultrasonic crystals
measuring left ventricular major and minor axes and parietal wall
thickness. The end-ejection pressure-calculated volume points were
significantly shifted to the left during SS as compared with those obtained
during AS both during a regular atrial pacing (150 beats/min) and during
spontaneous heart rate. Postpacing beats were not different during AS and
SS. During AS, end-systolic volume was larger after short intervals (SI)
between beats (22.5 +/- 1.6 ml) than after long intervals (LI; 20.8 +/- 1.7
ml) for a smaller end-systolic pressure (P less than 0.001). This
difference was minimal during SS. When SS was compared with AS, the
end-systolic and end-ejection pressure-volume points were significantly
shifted to the left after SI but not after LI. This suggests an
acceleration of the restitution process during SS that modifies ventricular
force-frequency relations and increases ventricular function as compared
with AS, particularly for high heart rates.
