Spatial and Temporal Heterogeneity of Depolarization and Repolarization May Complicate Implantable Cardioverter Defibrillator Therapy in Brugada Syndrome

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Abstract
Dynamic variations in electrophysiologic phenomena inherent to the Brugada syndrome may complicate therapy with implantable cardioverter defibrillators (ICDs). Between 1997 and 1999, 3 of 7 patients with Brugada syndrome (1 man and 2 women, mean age 42 years) received an ICD. During follow-up, 2 patients experienced multiple inappropriate shocks. Simultaneously with dynamic changes in the surface ECG, endocardial ECGs revealed a dynamic decrease in the right ventricular R wave and an increase in the corresponding T wave, resulting in T wave oversensing. With ajmaline administration, these dynamic changes in endocardial signals were reproducible at different right ventricular sites, whereas left ventricular epicardial signals remained stable. Incremental AAI pacing and exercise stress testing resulted in similar changes in right ventricular endocardial signals, but normalization of the surface ECG apart from progressively increasing S waves in leads II, V5, and V6. Orciprenaline administration had no effect on ECG phenomena. After implantation of a left ventricular epicardial lead for sensing and pacing, no inappropriate tachycardia detection recurred. These findings demonstrate that, in Brugada syndrome, spontaneous or ajmaline-induced changes in the surface ECG may be paralleled by significant variations in the right ventricular endocardial electrogram that may result in ICD malfunction. Implantation of a left ventricular epicardial lead for sensing and pacing may be the ultimate successful approach in certain patients. To assure proper ICD function, ajmaline testing during ICD implantation appears to be helpful.