Dynamic ST-Segment Elevation in Massive Pulmonary Embolism Captured by Holter Electrocardiography: A Case Report.

ST-segment elevation on a post-cardiac arrest electrocardiogram (ECG) is traditionally viewed as a hallmark of acute coronary occlusion. However, this finding can also arise from non-coronary etiologies like massive pulmonary embolism (PE), creating a high-stakes diagnostic dilemma. An 83-year-old woman hospitalized for trauma developed cardiac arrest with pulseless electrical activity (PEA). Immediate post-resuscitation ECG showed marked ST-segment elevation in leads V1-V4, II, III, and aVF, suggesting extensive myocardial infarction. A point-of-care echocardiogram showed severe right ventricular dilation, raising the suspicion of PE, which was confirmed by computed tomography. Fortuitously, a Holter monitor was attached, capturing the sequence of ECG changes before and after the onset of PE. It revealed that ST-segment elevation appeared after the onset of cardiac arrest and gradually decreased thereafter. The patient was successfully treated with anticoagulation. This case suggests that post-arrest ST-segment elevation in PE may reflect dynamic right ventricular strain and supply-demand mismatch, rather than fixed coronary occlusion. Recognizing the "dynamic" nature of these ECG changes, alongside rapid echocardiographic assessment, is essential to avoid unnecessary emergent coronary angiography and ensure timely treatment for PE.