Introduction: The incidence of ventricular fibrillation (VF) in asymptomatic patients with Brugada-type ECG is not high but it cannot be negligible. Risk markers for predicting VF are usually based on results of analysis in symptomatic patients and they have not been determined for asymptomatic patients. Symptomatic patients should have an advanced arrhythmogenetic substrate and risk factors for recurrent VF can be different from risk factors for the first VF episode.
Hypothesis: The risk factors for VF in symptomatic high-risk patients will be different from those in asymptomatic patients.
Methods: The patients group was consisted of 471 patients with Brugada syndrome and we divided the subjects into two groups; Asymptomatic (n=326) and Symptomatic groups (patients with syncope: n=122 and patients with VF: n=23). We analyzed clinical characteristics (age, gender, family history of sudden death, SCN5A mutation) and ECG markers. ECG markers included PQ, QRS, QT and Tpeak-Tend (Tpe) intervals, ST level, spontaneous type 1 ECG, early repolarization (ER) and fragmented QRS (fQRS). fQRS was defined as existence of multiple spikes (>2 spikes) within QRS complex in two contiguous leads.
Results: During follow-up (91±64 months), 41 patients experienced VF events (Asymptomatic: n=10, Symptomatic: n=31). Univariate analysis showed that spontaneous type 1 ECG, wide QRS (≥107ms), long Tpe interval (≥ 95ms), high ST level (≥ 0.52mV) and fQRS were common predictors for VF in both groups. Moreover, long QT interval (≥ 420ms) and ER were also predictors for recurrent VF in Symptomatic group. Clinical characteristics were not associated with VF in both groups. Multivariate analysis showed that fQRS was a significant risk marker for VF in both groups (Asymptomatic group: hazard ratio [HR] 4.7, confidence interval [CI] 1.2-31.2, p<0.05, Symptomatic group: HR 12.7, CI 2.5-235.4, p<0.01). Long Tpe interval and ER were independent predictors for VF in the Symptomatic group (Tpe: HR 3.0, CI 1.3-9.0, p<0.05, ER: HR 3.3, CI 1.5-8.1, p<0.01).
Conclusions: fQRS is a common risk marker for VF in both asymptomatic and symptomatic patients, whereas Tpe interval and ER are predictors for recurrent VF. The risk factors for VF were different between asymptomatic and symptomatic patients.