Early/Subtle electrocardiography features of acute coronary syndrome and ST-Segment elevation myocardial infarction

Chest pain is one of the most common presenting complaints in the emergency department. Interpreting a 12-lead electrocardiography (ECG) for evidence of ischemia is always challenging. Frank ECG changes such as ST-segment elevation and ST-segment depression can be easily identified by emergency physicians. However, identifying subtle or early features of ACS in the 12-lead ECG is essential in preventing significant mortality and morbidity from ACS. In the following case series, we describe five of the subtle/early ECG changes of ACS, namely (1) T-wave inversion in lead aVL; (2) terminal QRS distortion; (3) hyperacute T-waves; (4) negative U-waves in precordial leads; and (5) loss of precordial T-wave balance. In all these cases, the initial 12-lead ECG showed only subtle/early ECG changes which were followed up with serial ECGs which progressed to STEMI.