The prevalence of concealed Brugada Syndrome in patients with paroxysmal atrial fibrillation

Funding Acknowledgements Type of funding sources: None. Background Brugada Syndrome (BS) is an inherited rhythm-disorder with risk of sudden-cardiac-death defined by a specific ST-segment elevation pattern in precordial ECG-leads either spontaneous or provoked by Na-channel-blocker-drug-provocation-test with Ajmaline and/or higher-precordial-intercostal-space (HICS)-ECGs. Scarce data denote that the prevalence of atrial fibrillation (AF) is higher in BS and most of the antiarrhythmic-drugs used in AF are contraindicated in BS. Purpose Our aim was to elucidate the frequency of BS in paroxysmal-AF (PAF) patients without heart-disease and reveal possible clinical/genetic relations. Methods Adult patients with an history of PAF less than 55-years-old were prospectively and consecutively evaluated with resting and HICS-ECGs, cardiac-examination and routine Ajmaline-drug-provocation-test (if not contraindicated). After the exclusion of subjects with any cardiac-disease, anti-arrhythmic-use, bundle-branch-blocks, pre-excitations and ventricular hypertrophies; 96 subjects ([mean±SD] age, 37.3±18, [range]18-55 years) were enrolled in the study (male n [%overall]:55 [57.2%]). All ECGs were interpreted manually by two experienced cardiologists for BS and Brugada-type-ECG-patterns (BTEPs). In 32 patients SCNA5A genetic tests were done (n: 15 BS(+) 17 BS(-) patients). In BS(+) patients, electrophysiological-study (EPS) with programmed-ventricular-stimulation (PVS) was also done and compared with the EPS parameters of BS(-) PAF patients that undergone AF-catheter-ablation-strategy (n: 30). Results Overall frequency of concealed-BS was 22,9% (n: 22 [male n: 14]). No spontaneous type-1 BTEP was found with HICS-ECGs and all BS diagnosis were Ajmaline-induced. The clinical characteristics of PAF patients with and without BS and statistical findings are presented in Table-1 and Figure-1. BS(+) patients were predominantly male, younger, slimmer, significantly more suffering from situational syncopal episodes and revealing more BTEPs by baseline HICS-ECGs. The SCN5A-mutation positivity was non-significant between BS(+) and (-) PAF patients (p= 0,80). Baseline heart-rates were lower and PR-intervals, P-wave-duration and Sinus-node-recovery-times were significantly higher in BS(+) patients. Only one BS(+) PAF patient with an history of syncope developed VF with 2 extra-beats in PVS and received an ICD. Conclusions Concealed-BS is found to be highly prevalent in middle-aged-subjects and especially males with PAF without an apparent cardiac-disorder. Knowing this considerably lethal condition might protect a vulnerable sub-group of patients from the deleterious effects of antiarrhythmics and risk stratification might confer an increased risk. Non-invasive/invasive indices regarding the delayed conduction features in atrial electrophysiological characteristics of BS(+) patients and a higher vagal state might be suggested as one of the probable mechanisms underlying the higher prevalence of AF in BS.