Dynamics of unipolar J-ST elevation coupled to bipolar delayed potentials on the epicardium in Brugada syndrome: a case report

BACKGROUND: The area of abnormal bipolar potentials in the right ventricular epicardium is recognized as an arrhythmogenic substrate in patients with Brugada syndrome (BrS); however, the correlation between local potentials and Brugada-type surface electrocardiograms (ECGs) remains unclear. CASE SUMMARY: A 49-year-old man with BrS who was hospitalized for refractory ventricular fibrillation underwent an electrocardiographic study with unipolar electrodes with the same bandwidth as surface ECGs. The right ventricular outflow tract epicardium showed abnormal bipolar potentials composed of split sharp and delayed dull components with coved-type J-ST elevation in the unipolar electrodes. The additional stimuli from the atrium gradually decreased the number of unipolar electrodes showing coved-type J-ST elevation along with a shortening of the local bipolar activation time. The pilsicainide provocation test induced a change in unipolar morphology from coved type to convex type and an intermittent local block of the divided and sharp components in bipolar electrodes. Of note, the unipolar J-ST elevation was not changed along with the localized conduction block in bipolar leads. DISCUSSION: The unipolar electrode waveforms during sinus rhythm change together with bipolar electrodes, consisting of sharp and blunt components in BrS. However, the convex-type J-ST elevation in unipolar leads persisted irrespective of the local conduction block in bipolar leads after pilsicainide provocation. These findings suggest the complexity of BrS mechanisms.