Effect of critical coronary stenosis on regional function of a segment remote from the acute ischemic bed. 
Limited information is available about the earliest manifestations of ischemia in an area of myocardium supplied by a critically constricted vessel following abrupt occlusion of another vessel.  The aim of this study was to describe quantitatively the mechanical behavior of different non-ischemic zones, with and without critical stenosis of the supplying artery.  Regional myocardial function was measured in 14 open-chest anesthetized dogs, with piezoelectric length and thickness crystals placed within the perfusion beds of the proximal left anterior descending and left circumflex arteries.  After baseline recordings, the left circumflex artery was critically constricted and the left anterior descending artery was abruptly occluded for 60 s. The same procedure was repeated after 30 min without stenosis of the artery.  After 45 min of recovery, the same protocol was repeated for a narrowed left anterior descending artery.  Regional performance was assessed by analyzing the phases of segmental contraction.  In the non-ischemic zone, isovolumic shortening and thickening and systolic shortening increased following left anterior descending artery occlusion, whereas, in the presence of critical constriction of the circumflex artery, isovolumic and systolic shortening and thickening did not increase.  Occlusion of the left circumflex artery resulted in a significant increase in isovolumic shortening and thickening, ejection shortening, systolic shortening and thickening, whereas, with critical constriction of the left anterior descending artery, the same segment did not exhibit hyperkinesis.  The compensatory potential of the non-ischemic zone seems to be dependent on whether there is restriction to its vascular supply.