Reversibly injured, postischemic @entity235 XXXX retains normal contractile reserve.

@entity296 @entity308 @entity4486 @entity235 @entity63 @entity1563 @entity1562 @entity460
Transient @entity1563 (15 minutes) does not result in irreversible @entity296 but is associated with a @entity308 of contractile function sustained for several hours to days ("stunned @entity1562 "). The defect in the contractile process responsible for this phenomenon has been suggested to be causally related to a reduced energetic state, altered excitation or excitation-contraction coupling, or damaged contractile filaments. The purpose of this study was to attempt to exclude one or more of these hypotheses by evaluating the contractile reserve of reperfused @entity1562 . Regional subendocardial segment function was measured (sonomicrometry) in a control region and in an area (treatment region) perfused by a carotid artery to anterior descending coronary artery bypass in 13 @entity4486 -anesthetized @entity235 . Dose-response curves were constructed from changes in segment shortening (%SS) in response to intracoronary @entity460 infusion before @entity63 and following 5 or 15 minutes of occlusion and reperfusion (30 minutes). @entity460 infusion before @entity63 resulted in dose-dependent increases in %SS in the treatment area to a maximum value of 36.6% from a preinfusion value of 25.5% (p less than 0.01), in the absence of changes in control region shortening (23.7%). After 15 minutes of occlusion and reperfusion, treatment area %SS had fallen to a @entity308 but stable level (46% of preischemic values; p less than 0.01). Subsequent @entity460 infusion at the same doses as in the preischemic trial produced increases in treatment segment function with return of shortening to control levels at an intermediate dose. At the highest dose, %SS was 35.4%, which was not different from the maximal value found in the preischemic trial. Alterations in heart rate and left ventricular systolic and diastolic pressures during @entity460 infusion were minor and similar before and after @entity63 . @entity460 -induced increases in regional segment shortening above control levels (113% of control) in reperfused @entity1562 were sustained with continuous infusion (30 minutes) without deleterious effects on subsequent function. These results demonstrate that stunned @entity1562 in this model retains a normal contractile reserve in response to @entity460 , suggesting that the mechanism responsible for postischemic contractile dysfunction involves @entity460 .
