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Corresponding author at: Heart Rhythm Center, Tokyo Medical University Hospital, Department of Cardiology, Tokyo Medical University, 6-7-1-Nishi-Shinjuku, Shinjuku, Tokyo 160-0023, Japan.
The presence of J waves in cases of ventricular fibrillation (VF) is known to be a risk for sudden cardiac death. Recently, the effectiveness of radiofrequency catheter ablation (RFCA) for early repolarization syndrome (ERS) has been reported.
The patient is a 30-year-old male with elevated J waves of 0.1 mV in the inferior leads, who had previously developed VF and undergone implantable cardioverter defibrillator (ICD) implantation. Because the VF from short coupled premature ventricular contraction (PVC) was presented, the RFCA of the triggered PVC was attempted. But it was unsuccessful due to no inducibility of the triggered PVC. After that, despite anti-arrythmia drug treatment, appropriate ICD shock for VF was observed. Although we decided to do a second ablation and evaluated epicardial arrhythmia substrate, no specific findings of early repolarization syndrome were found in the electrophysiological study. Finally, we considered that the cause of VF was short-coupled variant of Torsade de Pointes, and PVC ablation was performed. VF has not occurred since. We consider that this is a rare case to evaluate the epicardial arrhythmogenic substrate of J wave.
Learning objective
Ablation of the epicardial arrhythmogenic substrate in patients with early repolarization syndrome (ERS) has been shown to be effective, but the relationship between abnormal epicardial potentials and the pathophysiology is unclear. In this case, J-wave and epicardial delayed potentials were not considered to represent obvious arrhythmogenic substrates. Ablation of the triggered premature ventricular contraction may be effective in ERS without apparent abnormal potentials.
Inherited arrhythmia syndromes that cause ventricular fibrillation (VF) are classified into long QT syndrome, short QT syndrome, Brugada syndrome, early repolarization syndrome (ERS), and catecholaminergic polymorphic ventricular tachycardia. ERS patients with J waves in the lower and/or lateral leads are known to be malignant with high risk of arrhythmic sudden death [
Early repolarization pattern is the strongest predictor of arrhythmia recurrence in patients with idiopathic ventricular fibrillation: results from a single centre long-term follow-up over 20 years.
]. Recently, epicardial delayed or split potential was reported as an arrhythmic substrate of VF in ERS, and radiofrequency catheter ablation (RFCA) is an effective therapeutic option to suppress VF in ERS [
]. Idiopathic ventricular fibrillation (IVF) was characterized as VF with no identified origin despite extensive diagnostic testing. Short-coupled variant of Torsade de Pointes (SCV-TdP) has been described as IVF triggered by premature ventricular contraction (PVC) originating from Purkinje fibers. RFCA of triggering PVC may eliminate recurrent episodes of VF [
We report a Japanese SCV-TdP case with bystander early repolarization in inferior leads.
Case report
The patient was a 30-year-old Japanese man who had no family history of heart disease and sudden cardiac death who was diagnosed with idiopathic VF 10 years previously and underwent implantable cardioverter defibrillator (ICD) implantation. RFCA of the triggered PVC was attempted at that time, but it was unsuccessful due to no inducibility of the triggered PVC. 12-Lead electrocardiogram (ECG) showed J waves of 0.1 mV in the inferior leads. The ambulatory ECG demonstrated polymorphic nonsustained ventricular tachycardia (NSVT) reproducibly from a short coupling period of the identical morphology of PVC (Fig. 1). These events dominantly occurred in the daytime or during physical activity. But the frequency of PVC was extremely low.
Fig. 1(A) Initial electrocardiograms (ECG) showing prominent J waves in the inferior leads (arrows) and short-coupled premature ventricular contraction (PVC) during sinus rhythm. The coupling interval for PVC is 275 ms. (B) ECG monitoring record of the short-coupled variant of torsade de pointes. No prominent change in J point is seen between before and after the appearance of tachycardia. The coupling interval for PVC is 200 ms.
Pilsicainide and epinephrine provocation tests revealed no prominent ECG of Brugada syndrome or long QT syndrome. VF recurred even during the use of several antiarrhythmic drugs, such as bisoprolol, verapamil, quinidine, bepridil, and cilostazol and the patient was referred to our hospital. Blood tests and echocardiography showed no abnormalities, and signal-averaged electrocardiography showed no late potential. We then decided to perform a second RFCA.
Electrophysiological study and catheter ablation
Firstly, we evaluated the arrhythmogenic substrate of the end and epicardium because PVCs were not expected to frequently appear according to the result of the previous ablation session.
EPS was performed during deep sedation by administration of intravenous propofol and fentanyl. Two mapping catheters were advanced to the right ventricular apex and coronary sinus through trans femoral puncture. We approached the epicardium by a standard subxiphoid puncture. Mapping was performed during sinus rhythm using an Advisor HD-Grid multipolar electrode catheter (Advisor™ HD-Grid, Abbott Laboratories, Abbott Park, IL, USA) and a three-dimensional mapping system (Ensite™ NavX™, Abbott, St Paul, MN, USA). No low voltage area (<1.5 mV) was obvious in the epicardium. However, delayed potentials were observed in the inferior wall region at the base of the ventricle. These potentials were delayed by 10 ms from the terminal of QRS. The timing of these delayed potentials was almost the same as the J wave in the inferior lead of ECG.
Extra stimulus from the right ventricular septum to the refractory period following 500 ms of 6 basic cycles did not show any additional delay of late potentials (Fig. 2). Drug provocation testing of pilsicainide at 1 mg/kg showed a mild delay of late potential but did not demonstrate an increase of J wave voltage. No fractionated electrograms were apparent.
Fig. 2(A) Fluoroscopic images of left ventricular epicardium during electrophysiological study. The Advisor HD-Grid multipolar electrode catheter is located on the inferior wall, as the most delayed area. (B) A delayed potential prolonged 10 ms beyond the terminal of the QRS complex corresponding to the J wave in the simultaneously recorded lead II of the electrocardiogram (arrow). (C) The HD-Grid multipolar electrode catheter is located on the inferior wall, which is the most delayed area. Extra stimulus from the right ventricular septum with a 240 ms coupling period shows no obvious delay in potentiation of the delayed potential (arrow).
From these results, J-wave and epicardial potentials were not considered to represent obvious arrhythmogenic substrates in this case.
Although VF and polymorphic NSVT were not induced, clinical PVC was reproducibly induced by programmed stimulation, we decided to perform ablation for triggered PVC. QRS morphology of PVC showed left bundle branch block and superior axis. The earliest activation site was found in the free wall of the right ventricle with 25 ms earlier than QRS onset. The unipolar electrode showed a QS pattern, but no preceding Purkinje potential was observed. The HD-Grid was placed on the contralateral epicardium at the site of earliest excitation. The potential at onset of PVC was clearly delayed compared to the endocardium (Fig. 3). Ablation of the endocardium at the site of earliest excitation using an irrigation catheter (Tacticath SE, Abbott, Abbott Park), with 30 W rendered PVC non-inducible. Subsequently, VF was not inducible with any programmed stimulation. ECG changes were not observed before or after ablation. During 18 months of follow-up, there was no recurrence of VF.
Fig. 3Ablation catheter is located at the site of earliest activation during the trigger premature ventricular contraction (PVC). The earliest excitation site is found in the free wall of the right ventricle, where potentials are recorded 25 ms before QRS onset. The unipolar electrode shows a QS pattern, but no preceding Purkinje potential. The Advisor HD-Grid multipolar electrode catheter is located on the epicardial contralateral site of the earliest site of endocardium during the trigger ventricular premature contraction. The potential at onset of PVC is delayed compared to the endocardium (arrow). The coupling interval for PVC is 275 ms.
Effect of a sodium-channel blockade on early repolarization in inferior/lateral leads in patients with idiopathic ventricular fibrillation and Brugada syndrome.
]. But our case did not show such a typical clinical manifestation of ERS. A recent study reported delayed or fractionated electrogram on the epicardial surface and triggering PVC was originated from this area in ERS [
]. The catheter ablation of these abnormal potentials can eliminate the triggered PVC and reduce VF episodes. These data suggested that the arrhythmogenic substrate is located in the epicardium in ERS [
]. This study showed that there are 2 phenotypes of ERS syndrome, one with late depolarization abnormalities predominantly at the right ventricular epicardium and the other without depolarization abnormalities. Depolarization abnormality is defined as fractionated electrograms exhibiting low voltage (<1 mV) and fractionation with prolonged duration (≥70 ms). The group with abnormal depolarization showed a J wave elevation accentuated with sodium channel blocker administration. In the group without depolarization, the triggering PVCs originated from the Purkinje network. In this group, J waves were observed in both the lower and lateral walls in >80 % of cases. The delayed potential was recorded in the inferior base of the epicardium in our case but was not prominent and there was no significant additional delay after the sodium channel blocker. PVC was not originated from the area with delayed potential and no preceding Purkinje potentials were observed. J waves were observed only in the lower wall induction.
It was reported that delayed potentials with Brugada syndrome were enhanced by extra stimulation from right ventricle [
]. The delayed potentials observed in the present case were not further delayed by extra stimulation. Thus, the present case is not consistent with the previously reported arrhythmogenic temperament of ERS, and the delay potentials observed in this case were considered to be non-arrhythmogenic substrates.
Another explanation of the mechanism of VF in this case was SCV-TdP. Polymorphic NSVT following the same morphology of PVC was recorded just after the episode of aborted VF. The ablation of the PVC has been reported to be effective to prevent VF events in SCV-TdP [
]. The issue of PVC ablation is that it is sometimes difficult to perform the activation mapping of PVC due to infrequent PVC. The prior ablation session failed for this reason. Fortunately, we were able to eliminate PVC in the 2nd session. Although the coupling interval of the PVC triggering poly VT and the ablated PVC were different, ablation successfully suppressed VF. The moderator band has been reported as the origin of PVC and Purkinje potential precedes PVC in half of the cases. The Purkinje network has been speculated to be involved in the mechanisms of PVC and VF [
]. We could not find the typical Purkinje potential advance to PVC at the successful ablation site and did not find an anatomical relationship with the moderator band, which is reported as an origin of PVC in SCV-TdP.
PVC has been reported as the trigger of VF and delayed potential in the epicardial area was considered as the substrate of VF in ERS. But the mechanism of VF events was still not clear and there were no data suggesting which is the dominant mechanism of VF in ERS. This case suggested that J wave was not always the substrate of VF in patients with IVF. The patient's specific therapeutic strategy should be necessary according to the careful electrophysiological observation in patients with IVF.
Conflict of interest
All authors have no conflicts to disclose.
Acknowledgments
We thank Mr Martin for a linguistic revision.
Funding
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
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