Electrocardiographic ST-segment elevation: The diagnosis of acute myocardial infarction by morphologic analysis of the ST segment

Acute myocardial infarction (AMI) is one of many causes of ST-segment eleva tion (STE) in emergency department (ED) chest pain (CP) patients. The morph ology of STE may assist in the correct determination of its cause, with con cave patterns in non-AMI syndromes and non-concave waveforms in AMI. Object ives: To determine the impact of STE morphologic analysis on AMI diagnosis and the ability of this technique to separate AMI from non-infarction cause s of STE. Methods: The electrocardiograms (ECGs) of consecutive ED adult CP patients (with three serial troponin I determinations) were interpreted in two-step fashion by six attending emergency physicians (EPs): 1) the deter mination of STE by three EPs followed by 2) STE morphologic analysis (eithe r concave or non-concave) in those patients with STE. The impact of STE mor phology analysis was investigated in the identification of AMI and non-AMI causes of STE. Acute myocardial infarction was diagnosed by abnormal serum troponin I values (>0.1 mg/dL) followed by a rise and fall of the serum mar ker; STE diagnoses of non-AMI causes were determined by medical record revi ew. Interobserver reliability concerning STE morphology was determined. Stu dy inclusion criteria included at least three troponin values performed in serial fashion no more frequently than every three hours, initial ED ECG, E D diagnosis, and final hospital diagnosis. Results: Five hundred ninety-nin e CP patients were entered in the study, with 171 (29%) individuals having STE on their ECGs. Of the 171 patients who had STE, 56 had AMI, 50 had unst able angina pectoris (USA-P), and 65 had non-coronary final diagnoses. Fort y-nine patients had non-concave STE, 46 with AMI and three with USA-P; no p atient with a non-coronary diagnosis had a non-concave STE morphology. The sensitivity and specificity of the non-concave STE morphology for AMI diagn oses were 77% and 97%, respectively; the positive and negative predictive v alues for nonconcave morphology in AMI diagnoses were 94% and 88%, respecti vely. interobserver reliability in the STE morphology determination reveale d a kappa coefficient of 0.87. Conclusions: A non-concave STE morphology is frequently encountered in AMI patients. While the sensitivity of this patt ern for AMI diagnosis is not particularly helpful, the presence of this fin ding in adult ED chest pain patients with STE strongly suggests AMI. This t echnique produces consistent results among these EPs.