The transient nature of the effect of ischemic preconditioning on myocardial infarct size and ventricular arrhythmia.
We sought to determine whether short periods of preconditioning ischemia limited infarct size in a model of low coronary collateral flow and whether the effects of preconditioning were transient or long-lasting. Rats underwent 90 minutes of coronary occlusion followed by reperfusion. In one group, the rats were preconditioned by three 3-minute occlusions, each separated by 5 minutes of reperfusion. The size of the myocardial infarcts were smaller in the preconditioned group (24.9 +/- 7.8% of the risk zone developed necrosis) versus the nonpreconditioned group (60.7 +/- 5.3%, p less than 0.01). In addition, the incidence of ventricular arrhythmias was reduced by preconditioning. However, when there was a delay of 1 hour or more between the brief episodes of preconditioning and the longer 90-minute occlusion, the beneficial effects of preconditioning were lost. Thus preconditioning reduced the volume of myocardium infarcted and the incidence of ventricular arrhythmias during a subsequent period of prolonged ischemia; however, these beneficial effects were transient.
Li
Y W
YW
Heart Institute, Hospital of the Good Samaritan, Los Angeles, CA 90017.
Whittaker
P
P
Kloner
R A
RA
D000818:Animals; D001145:Arrhythmias, Cardiac / Q000517:prevention & control*; D003097:Collateral Circulation / Q000502:physiology; D003250:Constriction; D003326:Coronary Circulation / Q000502:physiology; D003327:Coronary Disease / Q000503:physiopathology; D004562:Electrocardiography; D005260:Female; D009203:Myocardial Infarction / Q000473:pathology*; D015428:Myocardial Reperfusion Injury / Q000473:pathology / Q000517:prevention & control*; D009206:Myocardium / Q000473:pathology; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors