The Prevalence and Clinical Features of Syncope in Patients with Concealed Brugada Syndrome

Abstract 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. Scarce data denote that the prevalence of non-arrhythmic syncope is high in BS and leads to diagnostic confusions. Head-up tilt test (HUT) is a diagnostic tool used to assess autonomic function in patients with suspicious syncopal events. Purpose Our aim was to elucidate the frequency of non-arrhythmic syncope in BS patients, compare it with non-BS population with suspicious syncope and reveal possible clinical relations. Methods Adult patients with an history of Ajmaline-induced BS and patients evaluated for suspicious syncope with non-arrhyhtmic-features without BS less than 55-years-old were prospectively and consecutively evaluated with resting and higher-inter-costal-space-ECGs (HICS-ECGs), cardiac-examination and routine HUT in our center. After the exclusion of subjects with resuscitated-sudden cardiac-death/documented-malignant-dysrhythmia, any cardiac-disease, anti-arrhythmic-use, bundle-branch-blocks, pre-excitations and ventricular hypertrophies; 52 BS(+) subjects ([mean±SD] age, 33,6±14, [range]18-55 years) (male n [%overall]:33 [63.2%]) and 35 age-sex matched BS(-)subjects ([mean±SD] age, 34,1±13, [range]18-55 years) were enrolled in the study. All ECGs and HUT test results were interpreted manually by two experienced cardiologists for BS and Brugada-type-ECG-patterns (BTEPs). Results The clinical characteristics of patients with and without BS and statistical findings are presented in Table-1. BS(+) patients were slimmer, revealing more BTEPs by baseline HICS-ECGs. Baseline heart-rates were lower, PR-intervals and P-wave-duration were significantly higher in BS(+) patients. HUT-positivity of BS(+) patients were significantly higher [(39% (n: 20 [male n: 13]) vs 19% (n: 7 [male n: 4]) (p= 0,01)] revealing significantly more mixed-syncope and orthostatic hypotension response in BS(+) subjects. No cardioinhibitory response was revealed. Conclusions Non arrhtymic syncope is found to be highly prevalent in middle-aged-subjects and especially males with BS (+) without an apparent cardiac-disorder. Knowing this considerably important clinical aspect might effect risk stratification algorithms and might prevent unnecessary high-risk interventions and device decisions. Non-invasive indices regarding the delayed conduction features in ECG characteristics of BS(+) patients and a higher vagal state might be proposed as one of the probable mechanisms revealing the higher prevalence of non-arrhythmic-syncope in BS.Table-1