Compressibility of perfused passive myocardium.
Yin, Frank C. P., Charles C. H. Chan, and Robert M. Judd.
Departments of Medicine, Biomedical Engineering and Radiology, the
Johns Hopkins University School of Medicine, Baltimore, MD 21287
APStracts 3:0202H, 1996.
In most theoretical analyses of the heart the tissue has been assumed
to be incompressible. Because the myocardium is extensively perfused
with distensible vessels, increasing the stiffness of the surrounding
tissue, as with contraction or passive stretching, should decrease
the volume of fluid in these vessels. Using a digital subtraction
angiographic method we quantified the amount of vascular volume
extruded from six passive, perfused canine interventricular septa
during cyclic biaxial loading from 300 to 900 gm force. At pressures
from 0 to 120 mm Hg the amount of fluid extruded during a loading
cycle varied from 2 to 4 ml/100 gm tissue at 0 and 120 mm Hg,
respectively. This volume change increased with perfusion pressure
and was significantly greater at 120 than at 0, 30, or 60 mm Hg. The
amount of fluid extruded on the same order as that estimated during
active contraction or with a 60 mm Hg change in perfusion pressure.
The finding that perfused myocardium is compressible implies that
results from existing analyses of the heart assuming
incompressibility are not realistic. Such analyses must account for
compressibility with e.g. mixture theory or other similar approaches.
Received 8 December 1995; accepted in final form 29 April 1996.
APS Manuscript Number H1141-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 8 May 96