AJP - Heart and Circulatory Physiology, Vol 249, Issue 3 585-H593, Copyright © 1985 by American Physiological Society
Measurement of peak systolic elastance in intact canine circulation with servo pump
D. K. Bogen, Y. Ariel, T. A. McMahon and W. H. Gaasch
Peak systolic elastance (Emax) was measured in the intact canine
circulation by means of a new experimental technique. In this technique the
heart is isolated from the circulation during a single systole and
subjected to controlled ventricular loads. An electropneumatic aortic
occluder is used to isolate the ventricle, and a servo-controlled syringe
pump is used to control the ventricular load. Because the experimental load
is applied for a single heartbeat only, ventricular function can be
measured without the interference of regulatory feedback mechanisms. In
eight dogs, weighing 17-42 kg, the relationship between changes in
endsystolic pressure and volume was determined from the single-beat
application of purely compliant loads. The end-systolic relations were
linear, and their slope, Emax, was inversely related to weight. The
observed relation between Emax and body weight allows comparisons to be
made between different preparations in which Emax has been determined.
Values of Emax obtained from the single-beat preparation were found to be
27-74% above those reported in isolated heart preparations and nearly
identical to those reported for in vivo or denervated in situ preparations.
