Arrhythmias from the Right Ventricular Moderator Band: Diagnosis and Management

Abstract

The moderator band in the right ventricle is being increasingly recognised as a source for arrhythmias in the absence of identifiable structural heart disease. Because it carries part of the conduction system from the right ventricle septum to the free wall, it is a source of Purkinje-mediated ventricular arrhythmias that manifest as premature ventricular contractions (PVC) or repetitive ventricular tachycardia. More importantly, short coupled PVCs triggering polymorphic ventricular tachycardia and VF have been localised to the moderator band and ablation of these Purkinje mediated PVCs can effectively prevent recurrent VF. The exact mechanism of arrhythmogenesis is still debated but stretch, fibrosis and ion channel alterations might be responsible. Arrhythmias originating in this region of the right ventricle may thus be another cause for idiopathic VF that is potentially treatable with catheter-based ablation techniques. Recognition of the typical PVC morphology can point to the moderator band as the source of idiopathic VF and an opportunity for timely intervention. The available data on the anatomy, electrophysiology and management options are reviewed.

Proarrhythmic Effect of RF ablation on the Right Ventricular Moderator Band

“…Monomorphic PVCs, non-sustained monomorphic VT and ventricular fibrillation are all documented arrhythmias originating from the MB. 1 The benign PVCs usually have a coupling interval in excess of 400 msec, as in the initial arrhythmia of the patient in this case. When PVCs trigger VF, coupling intervals are typically short, less than 300 msec.…”

“…The right ventricular moderator band (MB) is increasingly being recognized as a source for PVCs and PVCmediated ventricular fibrillation. 1 The moderator band extends from the septo-marginal trabeculations on the RV side of the septum and extends to the anterior papillary muscle. It carries fascicles of the right bundle within it that serve to rapidly activate the RV free wall.…”

Pre-síncope y ablación de la contracción ventricular prematura con origen en la banda moderadora

“…6 Mapping PVC from MB could be an issue, therefore some strategies should be considered to increase the chance of success as medication drips used during mapping a PVC as isoproterenol or dobutamine iv, pacing during mapping to induce PVC, pace mapping approaches, even using multipolar catheters as Pentaray (Biosense Webster, Diamond Bar, California), to collect as many activation points as you can on one touch. 17 The moderator band contains Purkinje system cells is consider a potentially arrhythmogenic structure, PVC from this structure can lead to a ventricular fibrillation; ablation can be a real challenge to a electrophysiologist; 18 even though, there are several aspects to consider: first the best target is difficult to achieve described as the identification of preceding Purkinje potential, pre ventricular activation, concordant morphology with pace mapping; second: stability is difficult to achieve in this structure, some strategies are been proposed: www.medigraphic.org.mx using a tridimensional mapping, intracardiac echocardiogram, even cryo catheters to freeze de area, 19 or a strategy who includes: a 3D mapping, ICE, radiofrequency and 23 mm balloon to cryoablation (freezing up to 4 minutes up to -47 o C) has been reported in the setting of a patient with already two failed procedures with successful results, 20 at last but not less the ablation with RF or Cryo could be trigger VF or VT, as a destruction of conduction cells during applications. 19 The percentages of the patients who might need a second procedure have been reported up to 60%; and the possible reasons to explain failed procedures or turn an early successful ablation into a fail therapy with increasing of PVC burden are: poor tissue contact with ablation catheter, lack of stability, insufficient deep lesions during ablation, and change of PVC exit (as a result of ablation points); though, a failed procedure can be dangerous to the patient if the clinic is syncope or even ventricular tachycardia or ventricular fibrillation.…”

Asymptomatic Athlete With Short-Coupled Premature Ventricular Contractions

“…Finally, the ERP observed in the inferolateral leads was considered to be of unclear prognostic significance according to an expert consensus ( 3 ); actually, the notched J-wave is thought to suggest a worse prognosis while an upsloping ST-segment is considered to suggest a good one ( 3 ). Our presumptive final diagnosis was short-coupled Purkinje PVCs originating at a medial insertion site of the moderator band near the right bundle branch ( 4 , 5 ).…”