Electrocardiographic prediction of the success of coronary reperfusion by intravenous thrombolytic therapy: an experimental study.

The accuracy of electrocardiograms (ECGs) in predicting the success of coronary reperfusion by intravenous (IV) thrombolytic therapy was studied in 49 canine acute myocardial infarctions (MI), induced by occlusive thrombus in the left anterior descending (LAD) coronary artery. Two hours after the onset of MI, urokinase (UK, 3 x 10(4) U/kg) was administered IV and the heart was observed for one further hour. LAD flow and epicardial ECGs were recorded continuously. LAD flow was restored by UK in 26 of 49 animals (Group I); restored LAD flow was stable in 17 of the 26 (Group IA) and unstable with repeated fluctuations in the other 9 (Group IB) during the follow-up period. No coronary reflow was obtained by thrombolysis in 23 of 49 animals (Group II). The best electrocardiographic criterion for predicting coronary reperfusion was reduction of ST elevation by more than 25%, which had a predictive accuracy of 86%. There was a significant correlation between the grade of improvement of coronary blood flow and reduction of ST elevation in Group IA (p less than 0.01), but not in Group IB, indicating that unstable coronary blood flow following thrombolysis due to residual thrombus appears to be one of the major factors preventing accurate prediction of coronary reperfusion with thrombolysis on the basis of changes in ST elevation.