A novel association between sinus node dysfunction and an SCN5A variant presenting as persistent symptomatic bradycardia in a young adult.

Sinus node dysfunction (SND), historically referred to as sick sinus syndrome, is characterized by symptomatic bradycardia due to an abnormality of the sinoatrial (SA) node or the interface between the sinoatrial node and the atrial tissue. SND encompasses inappropriate sinus bradycardia, ectopic atrial bradycardia, sinoatrial exit block, sinus pause, sinus node arrest, tachycardia-bradycardia syndrome, chronotropic incompetence, and isorhythmic dissociation. Causes of SND are divided into intrinsic and extrinsic.