Evolution of Human Scar-Related Ventricular Tachycardia Mapping for Exploring Mechanisms of Reentry Circuits.

Ventricular tachycardia (VT) can originate from diseased myocardium resulting from ischemic or nonischemic cardiomyopathy. Scar-related VT is predominantly sustained by reentrant circuits within areas of myocardial scar. The therapeutic target within these circuits is the isthmus-an electrically insulated pathway bounded by electrical barriers. To elucidate the mechanisms of isthmus formation and the structural characteristics of VT circuits, electrophysiological mapping during VT has advanced in parallel with technological innovations, including intraoperative mapping, electroanatomical mapping, and, more recently, high-density mapping using multipolar catheters. We have recently characterized VT circuits involving the intramural component and proposed a hyperboloid model to conceptualize three-dimensional VT propagation. Furthermore, we demonstrated that the majority of isthmus boundaries are formed by anatomically fixed lines of conduction block, as identified by substrate mapping. Novel technologies, such as a frequency analysis of intracardiac electrograms and micro-mapping catheters for the coronary vessels, have also been developed to investigate intramural VT circuits.