AJP - Heart and Circulatory Physiology, Vol 244, Issue 2 186-H193, Copyright © 1983 by American Physiological Society
Local auxotonic systolic force and work in canine right ventricular free wall
H. Piene and J. W. Covell
Regional auxotonic force (F) and segment length (SL) were measured in the
right ventricular (RV) free wall of 10 anesthetized dogs. F was obtained
with a Feigl force gauge and SL with ultrasonic crystals positioned in the
inflow or outflow region and in the longitudinal or transverse direction.
Although the time courses of right ventricular pressure and force were
almost identical, the timing of right ventricular ejection had little
relationship to specific parts of the force-segment-length loop. Thus local
F vs. SL loops were of irregular form signifying local lengthening or
shortening in isovolumic periods. Local work, i.e., F vs. SL loop area,
increased linearly with cardiac output (CO), which was varied by volume
expansion or reduction. A predominant contribution to total RV work from
any particular region and direction was not observed. A "local contribution
factor" [eta, defined as (local work/local area)/(total RV work/free wall
area)] fell with increased CO from 2.1 +/- 0.5 at 1.1 l/min to 0.7 +/- 0.2
at 4.8 l/min. This observation suggests that transformation of local into
total work became more efficient at higher CO or that structures other than
the free wall became increasingly important for RV pump function at higher
output levels.
