Coronary artery resistance changes depend on how the surrounding
myocardial tissue is stretched.
Sipkema, P., H. Yamada, and F. C. P. Yin.
Department of Physiology, Free University, Amsterdam, 1081 BT The
Netherlands, Department of Micro System Engineering, Nagoya
University, Nagoya 464-01 Japan, Cardiology Division, Johns Hopkins
University, Baltimore, Maryland 21287, USA
APStracts 2:0400H, 1995.
Deforming the tissue surrounding a coronary artery may change its
hydraulic resistance. In excised blocks of dog left ventricular walls
we examined how resistance (R) of a maximally dilated branch of a
circumflex coronary artery was affected by 10% stretching of the
tissue from its unloaded state first parallel, then perpendicular to
the vessel axis (with the orthogonal dimension held constant) and
finally biaxially. At 30 mm Hg transmural pressure (Ptm) R per
segment length (mm Hg x min / ml x cm) increased significantly from
the unloaded value of 0.0233+0.0031 (mean +/- SEM) to 0.0445+/-0.0073
and 0.0505+/-0.0090 during parallel and biaxial stretch,
respectively. At Ptm of 80 mm Hg unloaded R decreased to
0.0111+0.0016 but did not change further with stretching. Stretching
an isolated circular vessel 10% does not produce nearly this large an
increase in R. A finite element model simulating an epicardial vessel
under our experimental conditions qualitatively predicted our results
and demonstrated the combined roles of size and shape changes.
Simulating a midwall arteriole surrounded by tissue predicted
qualitatively similar results as for an epicardial vessel. Thus,
mechanical interaction between a coronary artery and surrounding
tissue depends on both transmural pressure and the direction of
stretching.
Received 17 February 1995; accepted in final form 23 August 1995.
APS Manuscript Number H150-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 23 September 1995.