THE ELECTROCARDIOGRAM IN THE INITIAL PHASE OF MYOCARDIAL-INFARCTION - AN AID FOR THERAPEUTIC STRATEGY

The electrocardiogram (ECG) remains the basic investigation for the diagnosis of acute myocardial infarction. The decision to institute intravenous thrombolytic therapy, which has revolutionised the treatment of myocardial infarction in recent years, requires the presence of ST segment elevation and a suggestive clinical history. Early Q waves and reciprocal ST changes may be helpful. The value of thrombolytic therapy has not been demonstrated in patients without ST elevation, especially considering the usually favourable prognosis of infarcts with normal ECGs or with only non-specific repolarisation changes. The initial ECG provides information about infarct size which is an essential prognostic factor. This evaluation is based on the topography (anterior or inferior), the amplitude of ST evelation and the number of leads in which these changes are observed. The initial analysis has two objectives : to evaluate the risk/benefit ratio of treatment in cases of relative contraindications to thrombolysis or with a doubtful diagnosis ; to select high risk patients (extensive infarcts) who may benefit from "salvage angioplasty" in the event of failure of thrombolysis : coronary angiography should be programmed from the onset as the ECG outcome does not allow prediction of the results of thrombolysis for the majority of these patients.