AJP - Heart and Circulatory Physiology, Vol 264, Issue 1 110-H116, Copyright © 1993 by American Physiological Society

ARTICLES

Changes in regional myocardial function and external work in exercising dogs with ischemia

S. Miyazaki, Y. Goto, B. D. Guth, T. Miura, C. Indolfi and J. Ross Jr
Division of Cardiology, University of California, San Diego 92093.

Changes in regional myocardial work of the nonischemic wall and left ventricular (LV) asynchrony of the nonischemic wall during exercise-induced ischemia were examined in seven conscious dogs instrumented with a micromanometer for LV pressure measurement and sonomicrometers for control and ischemic wall thickness and LV external short and long axes. Ischemia was produced during steady-state exercise by a pneumatic constrictor on the left circumflex coronary artery. Time difference between peak thickening of control (anterior) and ischemic (posterior) walls was measured as an index of LV asynchrony. LV pressure-wall thickness loop area of both the control wall (LVP-CW loop) and ischemic wall was calculated as an index of regional myocardial external work. With ischemia during exercise, peak LV pressure decreased by 11%, and time difference of peak thickening in the two walls increased, accompanied by marked deformation of the LVP-CW loop during early relaxation, which was related to protodiastolic thickening of the ischemic wall. Thus, despite a significant increase in percent systolic thickening during exercise, loop area of control wall was not enhanced. These changes of the LVP-CW loop were confirmed by calculation of stress-strain loop areas as an additional index of regional myocardial external work but having true dimensions of work. Stress-strain loop area in the control wall during ischemic exercise showed a similar value to that during control exercise, thereby confirming lack of compensatory increase. Thus, during exercise-induced ischemia, regional myocardial external work in the normal region does not increase despite an increase in systolic wall thickening.(ABSTRACT TRUNCATED AT 250 WORDS)

This article has been cited by other articles:

				J. G. Barra, A. J. Crottogini, P. Willshaw, E. C. Lascano, and R. H. Pichel Contribution of myocardium hydraulic skeleton to left ventricular wall interaction and synergy in dogs Am J Physiol Heart Circ Physiol, August 1, 2004; 287(2): H896 - H904. [Abstract] [Full Text] [PDF]

				H. Post, R. Schulz, P. Gres, and G. Heusch No involvement of nitric oxide in the limitation of beta -adrenergic inotropic responsiveness during ischemia Am J Physiol Heart Circ Physiol, December 1, 2001; 281(6): H2392 - H2397. [Abstract] [Full Text] [PDF]

				T W Koh, G S Carr-White, A C DeSouza, F D Ferdinand, J R Pepper, and D G Gibson Effect of coronary occlusion on left ventricular function with and without collateral supply during beating heart coronary artery surgery Heart, March 1, 1999; 81(3): 285 - 291. [Abstract] [Full Text]