NONUNIFORM RECOVERY OF SEGMENT SHORTENING DURING REPERFUSION FOLLOWING REGIONAL MYOCARDIAL-ISCHEMIA DESPITE UNIFORM RECOVERY OF ATP

Objective: This study focused on transmural postischaemic recovery of ATP and regional contractile function related to reversible and irreve rsible tissue injury. Methods: Fifty anaesthetised open-chest cats wer e randomised into two groups. Group I: 10 min of LAD occlusion (n = 10 ) and 10 min of LAD occlusion followed by 180 min of reperfusion (n = 15). Group II: 40 min of LAD occlusion (n = 10) and 40 min of LAD occl usion followed by 180 min of reperfusion (n = 15). Histochemical stain ing (TTC) was performed in hearts from 5 additional cats subjected to 40 min of LAD occlusion and 180 min of reperfusion. Regional function was measured by sonomicrometry in the circumferential (CIRC) and longi tudinal (LONG) axis of the anterior left ventricular midwall. Myocardi al blood flow was measured with radiolabelled microspheres. Adenine nu cleotides in the subepi- and subendocardium were measured with high-pr essure liquid chromatography after LAD occlusion and after reperfusion . Results: Ten minutes of ischaemia induced a transmurally uniform ATP depletion. Repletion of ATP following reperfusion was transmurally un iform. Recovery of regional shortening was non-uniform with better rec overy in CIRC (76 +/- 8% vs. LONG; 46 +/- 10%, P < 0.05). Forty minute s of ischaemia induced a more severe ATP depletion in the subendocardi um compared to the subepicardium. A slight recovery of ATP following r eperfusion was transmurally uniform. Recovery of function was present only in CIRC (48 +/- 6%). Tissue blood now showed a transmurally homog enous flow restriction during ischaemia and uniform recovery following reperfusion. TPC staining demonstrated predominantly subendocardial i nfarctions following 40 min of regional ischaemia. Conclusions: Postis chaemic recovery of regional function is non-uniform and independent o f ATP repletion and collateral blood flow during ischaemia. Absence of functional recovery in LONG is associated with development of infarct ion.