Objective Brugada syndrome (BS) is an inherited electrical cardiac disorder characterized by right bundle branch block pattern and ST segment elevation in leads V1 to V3 on surface electrocardiogram that can potentially lead to malignant ventricular tachycardia and sudden cardiac death. About 20% of patients have mutations in the only so far identified gene, SCN5A, which encodes the α-subunit of the human cardiac voltage-dependent sodium channel (hNa_v1.5). Fever has been shown to unmask or trigger the BS phenotype, but the associated molecular and the biophysical mechanisms are still poorly understood. We report on the identification and biophysical characterization of a novel heterozygous missense mutation in SCN5A, F1344S, in a 42-year-old male patient showing the BS phenotype leading to ventricular fibrillation during fever.

Methods The mutation was reproduced in vitro using site-directed mutagenesis and characterized using the patch clamp technique in the whole-cell configuration.

Results The biophysical characterization of the channels carrying the F1344S mutation revealed a 10mV mid-point shift of the G/V curve toward more positive voltages during activation. Raising the temperature to 40.5°C further shifted the mid-point activation by 18mV and significantly changed the slope factor in Na_v1.5/F1344S mutant channels from − 6.49 to − 10.27mV.

Conclusions Our findings indicate for the first time that the shift in activation and change in the slope factor at a higher temperature mimicking fever could reduce sodium currents' amplitude and trigger the manifestation of the BS phenotype.