Diagnostic and prognostic importance of comparing the initial to the previous electrocardiogram in patients admitted for suspected acute myocardial infarction.

Two hundred fifty-eight patients were admitted to the hospital for suspected acute myocardial infarction. Electrocardiograms recorded on admission (initial ECG) and the most recent available electrocardiogram recorded before admission (previous ECG) were compared to determine whether changes from the previous to initial ECG predicted acute myocardial infarction or complications of coronary artery disease. Initial ECGs were classed as either positive or negative, with positive indicating either infarction, injury, ischemia, strain, left ventricular hypertrophy, left bundle branch block, or paced rhythm. Negative ECGs were those that did not include any of the positive criteria. Positive and negative ECGs were subgrouped as showing change or no change from previous ECG. We found that patients with a negative initial ECG that had changed from the previous ECG had a 2.1 times greater risk for requiring interventions than those patients whose ECGs were unchanged. We also found that patients with a positive initial ECG that had changed from the previous ECG had a greater risk for interventions (2.0 times), complications (2.6 times), life-threatening complications (4.2 times), and acute myocardial infarction (6.6 times) than the sum of patients in all other ECG categories. We conclude that change is a useful predictor for interventions in patients with negative initial ECGs and a useful predictor for interventions, complications, and acute myocardial infarction in patients with positive initial ECGs.