Appearance of J wave in the inferolateral leads and ventricular fibrillation provoked by mild hypothermia in a patient with Brugada syndrome

Introduction Patients with Brugada syndrome (BrS) are recognized as having a high risk for sudden cardiac death owing to ventricular fibrillation (VF). The electrocardiogram (ECG) pattern in BrS is dynamic and variable, and often the typical pattern is concealed. Multiple factors have been shown to influence ST-segment elevation in BrS patients and suspected cases of BrS. These factors include changes in heart rate, body temperature, autonomic tone, glucose-induced insulin production, full stomach test, sodium channel blockers, and so on. A high prevalence of the J wave in the inferolateral leads was reported in patients with idiopathic ventricular fibrillation compared with control subjects in a case-control study. Subsequent studies confirmed a high prevalence of J wave as a risk marker for VF in various pathologic conditions, including BrS, vasospastic angina, acute myocardial infarction, and hypothermia. A J wave in the inferior leads was also associated with increased cardiac mortality in the general population. Appearance and augmentation of the J-wave amplitude were modulated by various factors, including hypothermia, bradycardia, and increased vagal tone. Several reports indicated that patients who had BrS with inferolateral J wave had a worse prognosis than those without. If BrS patients showing inferolateral J wave have a wide range of the arrhythmogenic substrate, these patients may have a high risk for VF provoked by the modifiers of the J wave. We present a case of BrS in which VF was provoked by mild hypothermia with appearance of prominent J wave in inferolateral leads.