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PRECONDITIONING IMPROVES MYOCARDIAL FUNCTION AND REFLOW, BUT NOT VASODILATOR REACTIVITY, AFTER ISCHAEMIA AND REPERFUSION IN ANAESTHETIZED DOGS
Author(s) -
Loke Kit E.,
Woodman Owen L.
Publication year - 1998
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/j.1440-1681.1998.tb02250.x
Subject(s) - dilator , medicine , cardiology , ischemia , occlusion , anesthesia , coronary occlusion , vasodilation , coronary circulation , artery , blood flow
SUMMARY 1. The present study examines whether three cycles of brief coronary artery occlusion and reperfusion (i.e. ischaemic preconditioning; PC) can prevent vasodilator dysfunction and the impairment of myocardial reflow caused by prolonged ischaemia. Coronary blood flow, left ventricular dP/dt, systemic arterial blood pressure and heart rate were measured in open‐chest anaesthetized dogs. 2. Sixty minute occlusion of the left circumflex coronary artery (LCx) and 60 min LCx reperfusion (ISC/REP; group 1) significantly reduced resting coronary blood flow (CBF, initial 29±3mL/min; ISC/REP 20±3mL/min, P <0.05 vx initial) and increased coronary vascular resistance (CVR, initial 4.1±0.6 mmHg/min per mL; ISC/REP 5.8±1.0 mmHg/min per mL, P <0.05 vs initial). By contrast CBF and CVR were not affected in dogs subjected to preconditioning before ischaemia (group 2: CBF, initial 24±4mL/min; PC+ISC/REP 23±4mL/min; CVR, initial 4.7±0.6 mmHg/min per mL; PC+ ISC/REP 5.3±1.0 mmHg/min per mL). These data suggest that ischaemic preconditioning prevents the ischaemia‐induced impairment of myocardial reflow. 3. Ischaemia and reperfusion impaired coronary dilator responses to the endothelium‐dependent dilator acetylcholine (ACBF, after ISC/REP: 50±6% of initial) and the endothelium‐independent dilator glyceryl trinitrate (ΔCBF, ISC/REP: 46±6% of initial). Despite the improvement in reperfusion in the preconditioned group, there was no significant improvement in responses to acetylcholine (PC+ISC/REP 52±6% of initial) or glyceryl trinitrate (PC+ISC/REP 59±6% of initial) after ischaemia and reperfusion. 4. The reduction in left ventricular dP/dt after ischaemia and reperfusion was significantly smaller in the preconditioned group indicating a lower level of impairment of cardiac contractility. In addition, we confirmed that preconditioning caused a significant reduction in infarct size and a reduction in the release of lactate dehydrogenase indicating less cardiac injury. 5. These results suggest that although ischaemic preconditioning was able to improve both myocardial reperfusion and contractility, it was not able to preserve vasodilator function. Such a reduction in vasodilator reserve could prevent adequate myocardial perfusion under conditions of elevated oxygen demand.