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A 24-year-old male who survived an aborted sudden cardiac death was admitted for a diagnostic work-up and a defibrillator implantation. He had experienced an episode of ventricular fibrillation at 5am during his sleep. His roommate promptly administered cardiac massage, and an emergency team subsequently performed a successful defibrillation. He recovered without any neurological deficits. No cardiac abnormality was detected on echocardiogram or coronary angiogram, and his medical history was unrevealing. However, the ECG showed a spontaneous Brugada type 1 pattern in lead V1, and after ajmaline administration also in lead V2, albeit only when recorded in the second intercostal space. Consequently, Brugada syndrome was diagnosed and a defibrillator was implanted. Ventricular fibrillation that was induced during the implantation procedure showed a very peculiar pattern, with the ventricular rate in lead V1 being half of that observed in other leads, while in lead V2 alternans in QRS amplitude was present. These observations suggested a local 2:1 conduction block (Fig. 1) over the right ventricular free wall. The mechanism underlying Brugada syndrome remains a matter of controversy (Wilde AA et al. J Mol Cell Cardiol, 2010; 4: 543–553). Data supporting a depolarisation abnormality mechanism, i.e. local conduction delay seen during the electrophysiology study (Nademanee K et al. Circulation, 2011; 12: 1270–1279), late potentials, and a right-bundle branch block QRS morphology, conflict with experimental data suggesting a repolarisation mechanism (Yan GX, Antzelevitch C, Circulation 1999; 15: 1660–1666). However, depolarisation abnormalities accentuate during a ventricular rate increase, in contrast to repolarisation abnormalities. In the current case, an increase in the rate during ventricular fibrillation/flutter resulted in an augmentation of the depolarisation problem over the right ventricle manifested by a local 2:1 block. These findings support the depolarisation theory of Brugada syndrome. We are not aware of such an ECG pattern having been previously reported. However, Wilde AA et al. (J Mol Cell Cardiol, 2010; 4: 543–553) reported ST-T alternans in lead V1 during an increase in the heart rate, and this also may be indicative of a similar phenomenon as in our case.

Ventricular fibrillation with a 2:1 conduction block over the right ventricle in a Brugada syndrome patient