Optimizing the initial 12-lead electrocardiographic diagnosis of acute myocardial infarction

Aims The optimum definition of ST elevation for diagnosis of acute myocardi al infarction, with respect to both the minimum height and the minimum numb ers of leads, is unknown. Furthermore, only 50% of patients with acute myoc ardial infarction present with ST elevation. We thus quantified the sensiti vity and specificity of different ST elevation criteria for diagnosis of ac ute myocardial infarction, and determined whether models incorporating mult iple QRST features in addition to ST elevation, could improve detection of acute myocardial infarction. Methods and Results The study population comprised 1190 subjects: 1041 cons ecutive patients presenting with chest pain (335 with acute myocardial infa rction) and 149 controls without chest pain. Subjects were randomly divided into a training set (587) and a validation set (603). ECG prediction model s for acute myocardial infarction incorporating different ST elevation crit eria and/or additional QRST features (Q waves, ST depression, T wave invers ion, bundle branch block, axes deviations, and left ventricular hypertrophy ) were developed in training Set patients using forward stepwise multiple l ogistic regression. Models were then prospectively tested in the validation set patients. greater than or equal to 1 mm Centre For Medical ST elevatio n model (based on greater than or equal to 1 mm at elevation in greater tha n or equal to 1 inferior/lateral leads, or greater than or equal to 2 mm ST elevation in greater than or equal to 1 anteroseptal leads) correctly clas sified 83.1% of subjects (55.8% sensitivity, 94.0% specificity). The choice of ST elevation definition had marked influence on the sensitivity (45.4-6 8.6%) and specificity (81.2-98.1%) for diagnosis of acute myocardial infarc tion. The addition of multiple QRST variables only marginally improved over all classification but did result in high specificity (92.6-96.1%). Conclusion Different definitions of 'significant' ST elevation led to marke d variations in sensitivity and specificity for diagnosis of acute myocardi al infarction. Multiple QRST features in addition to ST elevation only marg inally improved overall classification. (C) 2000 The European Society of Ca rdiology.