Idiopathic Accelerated Idioventricular Rhythm or Ventricular Tachycardia Originating From the Right Bundle Branch

Abstract

Background— Accelerated idioventricular rhythm (AIVR) or ventricular tachycardia (VT) originating from the right bundle branch (RBB) is rare and published clinical data on such arrhythmia are scarce. In this study, we will describe the clinical manifestations, diagnosis, and management of a cohort of patients with this novel arrhythmia. Methods and Results— Eight patients (5 men; median age, 25 years) with RBB-AIVR/VT were consecutively enrolled in the study. Pharmacological testing, exercise treadmill testing, electrophysiological study, and catheter ablation were performed in the study patients, and ECG features were characterized. All RBB-AIVR/VTs were of typical left bundle-branch block morphology with atrioventricular dissociation. The arrhythmias, which demonstrated chronotropic variability, were often isorhythmic with sinus rhythm and were accelerated by physical exercise, stress, and intravenous isoprenaline infusion. The rate of RBB-AIVR/VT varied from 45 to 200 beats per minute. Two patients experienced syncope, and 3 had impaired left ventricular function. Metoprolol was proven to be the most effective drug to decelerate the arrhythmia rate and relieve symptoms. Electrophysiology study was performed in 5 patients and the earliest activation with a sharp RBB potential was localized in the mid or distal RBB area. Catheter ablation terminated the arrhythmia with subsequent RBB block morphology during sinus rhythm. During follow-up, patients’ symptoms were controlled with normalization of left ventricular function either on metoprolol or by catheter ablation. Conclusions— RBB-AIVR/VT is an unusual type of ventricular arrhythmia. It can result in significant symptoms and depressed ventricular function and can be successfully treated with catheter ablation.

Two apparently remote types of ventricular tachycardia from a single right bundle branch focal source

“…In addition, both VAs may exhibit the same electrocardiogram pattern with LBBB morphology, late precordial transition in leads V5-V6, rapid downstroke of the QRS complex in the precordial leads, and left superior frontal plane axis (similar to the type 1 VT in our case) 7, 8. Although we did not compare electroanatomic activation maps acquired during both VT types, several features support a rather distal RBB source.…”

“…Although we did not compare electroanatomic activation maps acquired during both VT types, several features support a rather distal RBB source. They include clinical manifestation as idioventricular rhythm or VT with chronotropic variability accelerating by physical exercise, stress of isoproterenol infusion (whereas previously described MB-related sources rather manifested as VPCs inducing ventricular fibrillation), spontaneous presence of proximal exit giving rise to the type 2 VT with right QRS axis deviation (which was not described in the MB-related VAs), and complete abolition of all VAs by septal ablation above/proximal to the MB insertion at a site with distal RBB potential accompanied by ablation-induced progression of incomplete into complete RBBB 7, 8. Furthermore, the MB length on intracardiac echocardiography (Figure 3) in relation to the sites of favorable pace mapping and the extent and location of the radiofrequency lesion did not support abolition of a pure MB-related source by targeting septal and free-wall MB insertions 7 …”

“…Distinction of a pure MB-related VT source from the distal RBB source close to the septal MB insertion may be vague and rather arbitrary, since the MB encompasses distal RBB Purkinje fibers, and sharp Purkinje system potential was observed at successful ablation sites in both VA types 7, 8. In addition, both VAs may exhibit the same electrocardiogram pattern with LBBB morphology, late precordial transition in leads V5-V6, rapid downstroke of the QRS complex in the precordial leads, and left superior frontal plane axis (similar to the type 1 VT in our case) 7, 8.…”

“…Idiopathic RV arrhythmia originating in the distal RBB or MB is a rare entity of unknown underlying reasons, although increased automaticity is the likely mechanism 7, 8, 9, 10, 11, 12, 13. The clinical manifestation suggesting focal VT does not exclude, for example, arrhythmogenic RV cardiomyopathy 1 .…”

“…In this case, confounding multiple VT morphologies were not related to obvious RV structural disease, and catheter ablation appeared the optimal treatment. Yet, the risk of the development of tachycardia-induced cardiomyopathy8, 11, 12, 13 or MB-related VPC-induced idiopathic ventricular fibrillation 7 emphasizes the need for a case-by-case assessment of sudden cardiac death risk and close monitoring before and after ablation in patients with similar arrhythmia.…”