Empirical Ablation to Prevent Sequential Purkinje System Recruitment: A Novel Therapy for Idiopathic Ventricular Fibrillation

Idiopathic ventricular fibrillation associated with long-coupled Purkinje ectopy

INTRODUCTION

Idiopathic ventricular fibrillation (IVF) is mainly associated with and triggered by short-coupled (R-on-T) ventricular ectopics. However, little is known about the risk of VF associated with long-coupled premature ventricular complexes (LCPVCs).

OBJECTIVE

To examine the prevalence and characteristics of IVF patients presenting with LCPVCs.

METHODS

Consecutive patients with IVF and PVCs from five arrhythmia referral centers were reviewed. We included patients presenting LCPVCs, defined as PVCs falling after the end of the T wave, with a normal QTc interval. We evaluated demographics, medical history, and clinical circumstances associated with PVCs and VF episodes. The origin of PVCs was determined by invasive mapping.

RESULTS

Seventy-nine patients with IVF were reviewed. Among them, 12 (15.2%) met the inclusion criteria (8 women, age 36 ± 14 years). Eleven patients had documented LCPVCs initiating repetitive PVCs or sustained VF, whereas 1 had only documented isolated PVCs. In 10 of 12 patients, PVCs were recorded showing both long and short coupling intervals of 418 ± 46 and 304 ± 33 ms, respectively. Mapping showed that PVCs originated from the left Purkinje in 10 patients, from the right Purkinje in 1 patient, and both in 1 patient. Compared to other patients from the initial cohort, IVF with LCPVCs was associated with a left-sided origin of PVCs (92% in long-coupled IVF vs. 46% of left Purkinje PVCs in short-coupled IVF, p = .004).

CONCLUSION

Long-coupled fascicular PVCs, traditionally recognized as benign, can be associated with IVF in a subset of patients. They can induce IVF by themselves or in association with short-coupled PVCs.

Mapping and ablation of ventricular fibrillation substrate

Ventricular fibrillation (VF) is a life-threatening arrhythmia and a common cause of sudden cardiac death (SCD). A basic understanding of its mechanistic underpinning is crucial for enhancing our knowledge to develop innovative mapping and ablation techniques for this lethal rhythm. Significant advances in our understanding of VF have been made especially in the basic science and pre-clinical experimental realms. However, these studies have not yet translated into a robust clinical approach to identify and successfully ablate both the structural and functional substrate of VF. In this review, we aim to (1) provide a conceptual framework of VF and an overview of the data supporting the spatiotemporal dynamics of VF, (2) review experimental approaches to mapping VF to elucidate drivers and substrate for maintenance with a focus on the His-Purkinje system, (3) discuss current approaches using catheter ablation to treat VF, and (4) highlight current unknowns and gaps in the field where future work is necessary to transform the clinical landscape.

The Interventricular Septum: Structure, Function, Dysfunction, and Diseases

Vertebrates developed pulmonary circulation and septated the heart into venous and arterial compartments, as the adaptation from aquatic to terrestrial life requires more oxygen and energy. The interventricular septum (IVS) accommodates the ventricular portion of the conduction system and contributes to the mechanical function of both ventricles. Conditions or diseases that affect IVS structure and function (e.g., hypertrophy, defects, other) may lead to ventricular pump failure and/or ventricular arrhythmias with grave consequences. IVS structure and function can be evaluated today using current imaging techniques. Effective therapies can be provided in most cases, although definitions of underlying etiologies may not always be easy, particularly in the elderly due to overlap between genetic and acquired causes of IVS hypertrophy, the most common being IVS abnormality. In this review, state-of-the-art information regarding IVS morphology, physiology, physiopathology, and disease is presented.

Contemporary Management of Complex Ventricular Arrhythmias

Percutaneous catheter ablation is an effective and safe therapy that can eliminate ventricular tachycardia, reducing the risks of both recurrent arrhythmia and shock therapies from a defibrillator. Successful ablation requires accurate identification of arrhythmic substrate and the effective delivery of energy to the targeted tissue. A thorough pre-procedural assessment is needed before considered 3D electroanatomical mapping can be performed. In contemporary practice, this must combine traditional electrophysiological techniques, such as activation and entrainment mapping, with more novel physiological mapping techniques for which there is an ever-increasing evidence base. Novel techniques to maximise energy delivery to the tissue must also be considered and balanced against their associated risks of complication. This review provides a comprehensive appraisal of contemporary practice and the evidence base that supports recent developments in mapping and ablation, while also considering potential future developments in the field.