Abstract 2712: Different Electrophysiological Characteristics Between Patients With Brugada Syndrome and Those With Idiopathic Ventricular Fibrillation
Background: Brugada syndrome (BS) is one of the variations of idiopathic ventricular fibrillation (IVF), however, its ECG patterns characterized by ST-segment elevation in the right precordial leads suggest that there are discriminative substrates in patients with BS compared with those with IVF. In this study, we thus examined whether there are any differences in electrophysiological characteristics between the 2 disorders.
Methods: Fourteen consecutive patients with BS (all males, 45±11 [SD] yrs) and 9 patients with IVF (8 males, 34±16 yrs) were studied. BS was diagnosed with coved-type ECG in the right precordial leads and documented or induced VF. Patients with IVF had documented VF but negative response to drug challenge test with sodium channel blockers. We assessed the electrical parameters and the effects of pilsicainide (1 mg/kg, IV in 10 min) on endocardial conductions in the right ventricular (RV) outflow. Endocardial conduction was defined as the onset of endocardial potential in the RV from the earliest QRS, and conduction delay (Δ duration) was calculated as the difference in the endocardial conductions in the vicinity of the administration of pilsicainide.
Results: VF was induced by programmed electrical stimulation (PES) in all patients with BS and those with IVF. However, VF was induced more easily (by two extra-stimuli) in the BS group than in the IVF group (10 out of 14 [71%] in the BS group vs. 2 out of 9 [22%] in the IVF group, P < 0.05). Under control conditions, QRS duration was longer in the BS group than the IVF group (117±16 vs. 103±14 msec, P < 0.05), and late potentials of single averaged ECG were positive in all patients with BS but none in the patients with IVF (RMS40, 13±4 vs. 38±20 μV, P < 0.01; LAS40, 48±7 vs. 28±7 msec, P < 0.001). ST-segment elevation in the right precordial leads in response to pilsicainide was noted in the BS group but not in the IVF group (V2, 0.26±0.12 vs. 0.03±0.03 mV, P < 0.001). Furthermore, pilsicainide significantly delayed endocardial conduction in the RV outflow tract in the BS group compared with the IVF group (Δ duration, 20±2 vs. 8±2 msec, P < 0.01).
Conclusions: These results suggest that the depolarized disturbance underlies in the patients with BS but not in those with IVF. The mechanisms of IVF remain to be elucidated.