Available online 30 January 2023

Author links open overlay panelAbstract

Ventricular tachycardias (VT) may initially show beat to beat oscillations but rapidly stabilize into a regular tachycardia with a stable cycle length. A persistently irregular ventricular tachycardia is a rare phenomenon.

We report a rare case of an “irregular” ventricular tachycardia with so pronounced oscillations in cycle length that it was initially misdiagnosed as atrial fibrillation with aberrant conduction. This ventricular tachycardia was incessant and resulted in a tachycardia induced cardiomyopathy refractory to several antiarrhythmic drugs. Mapping of the right ventricle demonstrated that the tachycardia had a focal origin in the moderator band close to its insertion into the anterior papillary muscle. Radiofrequency ablation eliminated the tachycardia with eventual normalization of left ventricular function. The moderator band and anterior papillary muscle of the right ventricle are known to be the source of short-coupled ventricular premature beats and regular ventricular tachycardias. However, an “irregular” ventricular tachycardia has not been previously reported to arise from these structures.

Introduction

The moderator band can be a source of ventricular premature beats, ventricular fibrillation, and sustained monomorphic ventricular tachycardia [1]. The anatomical structure, histology, and electrophysiological properties of the moderator band differ from the surrounding myocardium and this disparity can account for short- coupled ventricular premature beats that can initiate ventricular fibrillation and also reentrant regular ventricular tachycardias using the moderator band as one limb of the reentrant circuit and the RV myocardial free wall and septum as the other limb [2]. However, an “irregular” monomorphic ventricular tachycardia has not been reported to originate from the moderator band or anterior papillary muscle.

Section snippetsCase presentation

A 40-year-old female with no significant past medical history except for depression controlled on Sertraline 100 mg daily, presented to the emergency department with a 24-h history of rapid palpitations and shortness of breath. Initial physical exam showed a patient in mild respiratory distress with a heart rate of 146 bpm, blood pressure of 119/71 mmHg, and respiratory rate of 20. There was no JVD, clear lung fields and irregular heart sounds without murmurs. Chest x-ray and routine blood

Electrophysiology study

Light sedation was provided with intravenous midazolam and fentanyl. Non-invasive continuous monitoring of the blood pressure was obtained with Finapres. Multipolar electrode catheters were percutaneously introduced through the femoral veins under ultrasound guidance and advanced to the coronary sinus, right atrial appendage, His bundle region and right ventricle. An 8 French intracardiac ultrasound catheter (AcuNav, Siemens, Sequoia) was percutaneously advanced through the left femoral vein

Ablation

Once the site of earliest ventricular activation was identified, a mapping/ablation deflectable externally irrigated catheter with contact force capability (Thermocool SmartTouch, SF, Biosense Webster) was advanced via the preformed sheath to the earliest ventricular activation site guided by the 3-D map reconstruction and intracardiac echocardiography. Three radiofrequency current applications were delivered at this site (10–30 watts). The third applications resulted in termination of the

Discussion

This case illustrates the rare presentation of an “irregular” monomorphic ventricular tachycardia originating from the moderator band that resulted in a tachycardia induced cardiomyopathy. This tachycardia had a focal origin in the moderator band close to its insertion into the anterior papillary muscle of the right ventricle.

The moderator band extends from the septum to the anterior papillary muscle of the right ventricle and contains within its muscular structure, the right bundle branch that

Funding

None.

CRediT authorship contribution statement

Marina L. Gonzalez: Conceptualization, Resources, Writing – original draft. Chenni S. Sriram: Writing – review & editing. Mario D. Gonzalez: Investigation, Data curation, Visualization, Writing – review & editing, Supervision, Project administration.

Declaration of Competing Interest

The authors declare that they have no conflict of interest.

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© 2023 Published by Elsevier Inc.