In the context of structural heart disease, ventricular tachycardia (VT) is related to surviving fibres in incomplete scar. New technologies which allow electroanatomic mapping at higher density and with smaller, more closely spaced electrodes have allowed new insights into the characteristics of VT circuits. VT isthmuses are complex structures, with multiple entrances, exits and dead ends of activation. The isthmus is frequently defined by regions of functional block and several VT circuits can be possible in a VT “critical zone”. In this review, we discuss these new insights and how they may improve VT ablation strategies, as well as discussing emerging technologies which may further develop our understanding.

Sudden cardiac death (SCD) is common and affects a heterogeneous group, from those with established cardiovascular disease to a population without structural heart disease and those with malignant inherited arrhythmic syndromes. Worldwide estimates are that 50% of all such deaths are linked to ventricular fibrillation (VF) [1]. In high-risk patients or resuscitated VF survivors, implantable cardiac defibrillators (ICD) are the cornerstone first-line therapy to abort further episodes [2,3]. However, ICDs do not prevent recurrent episodes and, even with antiarrhythmic therapy, up to 20% of patients with ICDs experience recurrent VF episodes and even electrical storms (multiple recurrences of ventricular arrhythmias over a short period of time), with a clear morbidity burden and increased mortality [4,5].Ventricular fibrillation (VF) is a common and life-threatening arrhythmia resulting in sudden cardiac death (SCD). Due to the inherent challenges of mapping VF in humans, the underlying mechanisms that initiate and sustain this common arrhythmia are still poorly understood. In high-risk patients and survivors of SCD, implantable cardioverter defibrillators (ICD) play a central role in treating VF episodes, however, ICDs do not prevent VF recurrences and patients remain at risk of electrical storm and multiple shocks that are often refractory to escalation of medical therapy. More recently, the utility of catheter ablation (CA) has extended to the treatment of VF storms. This review will focus on updates in elucidating the mechanism of VF leading into the role and indication of CA as a treatment strategy.

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