AJP - Heart and Circulatory Physiology, Vol 245, Issue 5 741-H748, Copyright © 1983 by American Physiological Society
Regional circumferential lengthening patterns in canine left ventricle
W. Y. Lew and M. M. LeWinter
We employed sonomicrometers in open-chest dogs to study lengthening of
short segments of circumferentially oriented myocardium located at the
base, midportion, and apex of the anterior left ventricular free wall. Left
ventricular pressure was varied by inferior vena caval occlusion and volume
expansion. Diastole was divided into rapid and slow lengthening phases.
Rapid lengthening was completed first at the basal site at each of three
successive levels of left ventricular diastolic pressure (LVDP). At the
base, significant further lengthening occurred during the slow lengthening
phase while at the apex virtually all lengthening was completed during the
rapid phase. At low LVDPs, peak lengthening rates (dl/dt) were greatest at
the apex. As LVDP was increased, regional differences in dl/dt diminished.
These results indicate that there is regional variation in the timing of
the phases of diastole and in lengthening patterns of the left ventricle.
The volume-dependent variation in lengthening rates that we observed is
consistent with the concept of regional differences in elastic recoil,
which may contribute to active ventricular filling.
