EP Substrate Underlying the ECG Phenotype and Electrogram Abnormalities in Brugada Syndrome | Journal Scan
What is the arrhythmogenic substrate in the Brugada Syndrome (BrS)?
Noninvasive electrocardiographic imaging (ECGI) was performed in 25 patients with BrS, six patients with right bundle branch block (RBBB), and seven normal control subjects. Surface electrocardiographic potentials were recorded on the torso with 250 electrodes and combined with heart and torso geometry obtained by computed tomography. The surface electrocardiographic potentials were used to construct epicardial potentials, unipolar and bipolar electrograms, and epicardial activation and repolarization maps.
The abnormalities found in the BrS patients were located in the right ventricular outflow tract (RVOT) and consisted of ST-segment elevation (STE), T-wave inversion, delayed activation, low amplitude, fractionation, delayed repolarization, and steep repolarization gradients. The heart rate was increased by exercise or isoproterenol infusion in six BrS patients, and this resulted in reduced STE and greater fractionation. In the RBBB patients, there was delayed activation in the entire right ventricle and no fractionation, ST-segment elevation, or repolarization abnormalities.
The authors concluded that the arrhythmogenic substrate in BrS consists of slow conduction and repolarization abnormalities in the RVOT.
ECGI allows noninvasive epicardial mapping and reconstruction of epicardial unipolar and bipolar electrograms. The findings of this study serve to validate in humans the results of experimental studies. Of note is that Nademanee and colleagues (Circulation 2011;123:1270-9) reported that epicardial catheter ablation at the anterior RVOT normalized the electrocardiographic abnormalities of BrS and prevented episodes of ventricular fibrillation. The findings of the present study provide an electrophysiologic rationale for this therapeutic approach to BrS.
Clinical Topics: Arrhythmias and Clinical EP, Noninvasive Imaging, Implantable Devices, EP Basic Science, Genetic Arrhythmic Conditions, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias
Keywords: Arrhythmias, Cardiac, Brugada Syndrome, Bundle-Branch Block, Catheter Ablation, Electrocardiography, Electrophysiology, Epicardial Mapping, Heart Conduction System, Heart Rate, Isoproterenol, Tomography, Ventricular Fibrillation
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