Functional Substrate Mapping: A New Frontier in the Treatment of Ventricular Tachycardia in Structural Heart Disease.

Functional substrate mapping has emerged as an essential tool for electrophysiologists, overcoming many limitations of conventional mapping techniques and demonstrating favourable long-term outcomes in clinical studies. However, a consensus on the definition of 'functional substrate' mapping remains elusive, hindering a structured approach to research in the field. In this review, we highlight the differences between 'functional mapping' techniques (which assess tissue response to the 'electrophysiological stress' using short coupled extrastimuli) and those highlighting regions of slow conduction during sinus rhythm. We also address fundamental questions, including the optimal degree of electrophysiological stress that best underpins the critical isthmus and the role of wavefront activation in determining the most effective ablation site.