Abstract
Diphenhydramine overdose is a dangerous condition that typically leads to symptoms of antimuscarinic toxicity and dysrhythmias. Left ventricular (LV) systolic dysfunction is a manifestation of diphenhydramine toxicity that commonly presents with electrocardiogram (ECG) findings of QRS prolongation. This article presents the case of a patient who was brought to the emergency department (ED) after a diphenhydramine overdose and was showing signs of antimuscarinic toxicity, with an ECG showing no signs of QRS interval prolongation. Point-of-care echocardiography and speckle tracking were performed, which showed a preserved ejection fraction (EF) and reduced global longitudinal strain (GLS), suggestive of subtle LV systolic dysfunction. The patient was treated with intravenous fluids and rivastigmine; his symptoms improved appropriately, and he was discharged the following day. This case report highlights the sensitivity of GLS in unveiling LV systolic dysfunction in patients with preserved EF and a normal ECG, showing its potential utility in patients presenting to the ED with substance overdoses.