Unmasking Atrial Septal Defect through an Incidental ECG Finding: The Crochetage Sign

Atrial septal defect (ASD) is a common congenital heart disease that often remains asymptomatic until adulthood. We present the case of a young construction worker in his early twenties who was rescued following a tunnel collapse and was incidentally found to have a large ostium secundum ASD during routine medical evaluation. A crochetage sign—a notch at the apex of the R wave in the inferior electrocardiogram leads—prompted further assessment. Transthoracic echocardiography confirmed a 38 mm ASD with right atrial and right ventricular dilatation, along with moderate tricuspid regurgitation. The patient subsequently underwent successful surgical closure of the defect, with an uneventful postoperative course. This case highlights the crochetage sign as a subtle yet clinically significant electrocardiographic indicator of ASD, warranting consideration even in asymptomatic individuals.