Electrophysiological and anatomical background of the fusion configuration of diastolic and presystolic Purkinje potentials in patients with verapamil-sensitive idiopathic left ventricular tachycardia

Purkinje Fibers in Canine False Tendons: New Anatomical and Electrophysiological Findings

Introduction

Purkinje system and false tendons (FTs) are related to ventricular arrhythmia, but the association between Purkinje fibers and FTs is not clear. This study investigated the associations of anatomical and electrophysiological characteristics between Purkinje fibers and FTs.

Methods and Results

We optimized the protocol of Lugol's iodine solution staining of Purkinje fibers to study the anatomical structure and originated a novel electrophysiological mapping method, named the direct visual mapping (DVM) method, to study the electrophysiological characteristics. By using the above-mentioned innovations in 12 dogs, we found the following. (1) There was no Purkinje fiber found 0.5 cm–1.0 cm below the valve annulus or on the leaflets or chordae tendineae of the mitral valve or adjacent to the top 1/3 of the papillary muscle. (2) Purkinje fibers existed in all FTs, including smaller and tiny FTs. (3) The Purkinje fibers contained in the FTs extended from the proximal to the distal end, and their electrophysiological characteristics were similar to the fibers on the endocardium, including anterograde, retrograde, and decremental conduction and automaticity.

Conclusions

Purkinje fibers are commonly found in FTs. The electrophysiological characteristics of the Purkinje fibers contained in FTs are similar to the fibers on the endocardium. FTs might have an anatomical and electrophysiological basis for ventricular arrhythmia.

Idiopathic Ventricular Premature Contraction and Ventricular Tachycardia: Distribution of the Origin, Diagnostic Algorithm, and Catheter Ablation

Idiopathic ventricular premature contractions (VPCs), defined as VPCs in the absence of obvious structural heart disease, are one of the common types of arrhythmia in clinical practice. They are sometimes complicated with non-sustained ventricular tachycardia (VT), and/or sustained VT with almost same QRS morphology in 12 leads ECG. Idiopathic VT (IVT) commonly occurs by focal mechanisms and the origins are distributed in a variety of sites in both ventricles. In this article, the clinical characteristics of IVT/IVPCs, the diagnostic algorithm, and how to ablate them will be reviewed.

Evaluation of left ventricular false tendons in children with idiopathic left ventricular tachycardia

BACKGROUND

Left ventricular false tendons (FT) traverse the ventricular cavity and are thought to have some association with idiopathic left ventricular tachycardia (ILVT). However, reported prevalence of FT varies widely, making correlation difficult. Superior echocardiographic windows of pediatric patients may permit better analysis of FT in ILVT. Our study describes the relationship between FT and ILVT in young patients.

METHODS

Retrospective case-control study of 30 ILVT patients with 98 controls compared for FT. Diagnosis of ILVT was made by electrocardiogram and clinical history, and for 25 patients was further confirmed by electrophysiology study (EPS). Presence of FT was identified by one blinded observer and verified by a second blinded observer. Presence of FT was then compared between ILVT patients and controls using Fisher's exact test.

RESULTS

Presence of FT did not differ significantly between patients and controls (53% vs 43%, P  =  0.40). Twelve FT patients (19%) had multiple FTs detected, though the incidence of ILVT was no higher in the setting of multiple FTs. A total of 25 patients with ILVT underwent EPS for intended ablation therapy, with ultimate success in 22/25 (88%) after one or more ablation sessions. Of the 25 EPS patients, FTs were present in 11, but precise correlation between successful ablation location and FT location was not possible since intraprocedural echocardiography was not performed in this patient group.

CONCLUSIONS

Presence of FTs did not differ between ILVT patients and controls. While FTs are not absolutely required for ILVT, they may still play a role in some cases.

Medical therapy to prevent recurrence of ventricular arrhythmia in normal and structural heart disease patients

INTRODUCTION

Recurrent ventricular arrhythmias (VA) are a source of significant morbidity in patients without structural heart disease (SHD) and also mortality in patients with SHD. The treatment goals for these two patient populations differ greatly. Areas covered: The secondary prevention of recurrent VA in patients without and with SHD will be reviewed, focusing on clinical data (especially randomized, controlled trials) in the literature as determined through searches in PubMed and ClinicalTrials.gov. This will include β blockers, non-dihydropyridine calcium channel blockers and antiarrhythmic drugs in both subgroups and non-antiarrhythmic medications in SHD. Expert commentary: The available options for medical therapy for VA in both normal hearts and SHD are insufficient, due to substandard efficacy and toxicities. While non-pharmacologic therapies may provide an excellent option, further drug development and randomized trials are needed, as is a reappraisal of the current mode of utilization.