Ventricular Tachycardia Isthmus Characteristics: Insights from High-density Mapping

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.