Action Potential Alternans in the Right Ventricular Outflow Tract in a Patient With Asymptomatic Brugada Syndrome

Abstract

Circ J 2009; 73: 580 -583 n both experimental and clinical studies, the pathogenesis of Brugada syndrome (BS) has been reported as depression or loss of the action potential dome in the right ventricular (RV) epicardium, which creates a transmural voltage gradient that may be responsible for the ST-segment elevation and also induce extrasystolic activity because of phase 2 reentry. 1-4 However, several reports show a high induction rate of ventricular fibrillation (VF) by programmed ventricular stimulation 5-8 and recent reports demonstrate that ventricular premature complexes occurring after administration of pilsicainide to unmask ST-segment elevation in the right precordial leads show left-bundle branch block and inferior axis, suggesting RV outflow tract (RVOT) origin 9-11 and increased inducibility of VF at the RVOT in BS. [2][3][4][5][6][7][8][9][10][11][12][13][14] Furthermore, several reports demonstrate T-wave alternans in the 12-lead ECG after administration of class Ic antiarrhythmic drugs. [14][15][16][17][18] This case report describes a patient with asymptomatic BS in whom monophasic action potentials (MAPs) recorded from the RVOT demonstrated alternans and VF was induced only when the extrastimuli were applied after a shorter MAP of the alternans. Case ReportA 71-year-old man who had frequent ventricular premature contractions after right hip joint surgery at the Nihon University Hospital was referred to the Cardiology Division. Twelve-lead ECG showed type II Brugada-type ECG and incomplete right bundle branch block (Figure 1). 19 The 12-lead ECG changed to type I Brugada-type ECG after administration of the class Ic antiarrhythmic drug, pilsicainide (Figure 2). He did not have a family history of sudden death or attacks of unconsciousness. Physical examination was normal and laboratory data were in the normal ranges, except for high total cholesterol level (250 mg/dl). Chest X-ray showed calcification of the aortic arch and echocardiography showed hypokinesis of the left ventricular anterior wall. The signal-averaged ECG showed border- (Received April 1, 2008; revised manuscript received April 30, 2008; accepted May 21, 2008; released online December 12, 2008 A 71-year-old man with frequent ventricular premature contractions after right hip joint surgery was referred to the Cardiology Division. Twelve-lead ECG showed type II Brugada-type ECG and signal-averaged ECG showed positive ventricular late potentials. The 12-lead ECG changed to type I Brugada-type after administration of the class Ic antiarrhythmic drug, pilsicainide. Ventricular fibrillation (VF) was reproducibly induced with double premature stimuli from the right ventricular outflow tract (RVOT) at a basic cycle length (BCL) of 400 ms. Monophasic action potentials (MAPs) recorded from the RVOT at a BCL of 400 ms showed MAP alternans and VF was only induced when extrastimuli were applied after a shorter MAP of the alternans. (Circ J 2009; 73: 580 -583)

Action potential wavelength restitution predicts alternans and arrhythmia in murine Scn5a+/− hearts

“…Scn5a +/− hearts further demonstrate fibrotic changes with ageing in common with the human condition (Jeevaratnam et al 2011). They also have an increased propensity to APD alternans (Matthews et al 2010) paralleling recent reports in humans (Kofune et al 2009; Liu & Chang, 2013). This may reflect their reduced Na + channel expression (Martin et al 2012 b ) leading to disturbances in θ, APD and refractoriness.…”

Abnormal Action Potential Duration Restitution Property in the Right Ventricular Outflow Tract in Brugada Syndrome

“…17 We also reported a case in which monophasic action potentials (MAPs) recorded from the RVOT at a basic cycle length (CL) of 400 ms showed MAP alternans, and VF was induced only when extrastimuli were applied after a decrease in the MAP duration (MAPD) of the alternans. 18 Thus we hypothesized that the RVOT contributes to RV Action Potential Restitution in BS the inducibility of VF in patients with BS undergoing programmed ventricular stimulation. To examine this hypothesis, we recorded MAPs from the RVOT to calculate the repolarization restitution slope during programmed ventricular stimulation.…”