The study population consisted of 68 individuals (55 males, mean age 44.8 ??#xA0;12.8 years) with spontaneous (n = 27) or drug-induced (n = 41) type 1 ECG pattern of BS. Twenty-eight subjects were symptomatic with a history of syncope (41.2 % ). SND was observed in 6 symptomatic subjects (8.8 % ), and was mainly attributed to sino-atrial block with sinus pauses. Two patients were initially diagnosed with SND, and received a pacemaker. Patients with SND displayed an increased P-wave duration in leads II and V2, PR interval in leads II and V2, QRS duration in leads II and V2, and increased QTc interval in lead V2 (p < 0.05). AH and HV intervals as well as corrected sinus node recovery time (cSNRT) were significantly prolonged in subjects with SND (p < 0.05). During a mean follow-up period of 5.0 ??#xA0;3.6 years, five subjects with a history of syncope suffered appropriate implantable cardioverter defibrillator (ICD) discharges due to ventricular arrhythmias (7.4 % ). None of those diagnosed with SND suffered syncope or ICD therapies.
SND is not an uncommon finding in subjects with type 1 ECG pattern of BS. The occurrence of SND in relatively young patients may deserve meticulous investigation including sodium channel blocking test.