[Exertional syncope: A diagnosis of long QT syndrome. A practice-oriented case report on risk stratification and management].

Introduction: We present the case of a 22-year-old medical student who experienced repeated episodes of syncope during physical exertion. Ini-tial investigations, including a neurological assessment and cardiac examinations involving electrocardiograms (ECGs) and Holter monitoring, were normal. During a subsequent volleyball match, however, she suffered cardiac arrest and required resuscitation and defibrillation with an automated external defibrillator (AED). Analysis of the AED recording revealed ventricular fibrillation (VF) and prompted further diagnostic testing. Long QT syndrome (LQTS) was diagnosed based on the clinical presentation, a prolonged QTc interval on the ECG and documented cardiac arrest with VF. Subsequent genetic testing identified a pathogenic variant in the KCNQ1 gene, confirming the diagnosis of type 1 LQTS. The patient was treated with beta blockers, and an implantable cardioverter-defibrillator (ICD) was implanted. This case highlights the diagnostic and prognostic significance of exercise-induced syncope as a high-risk symptom requiring careful cardiological evaluation, even when initial investigations are unremarkable. It emphasises the high didactic value of AED data analysis and illustrates the application of current guidelines in the management of cardiac channelopathies.