Background: In scar-related ventricular tachycardia (VT) ablation, conduction slowing area (CSA) during sinus rhythm (SR) has gained interest as a promising ablation target. SR activation mapping divided into 8 isochrones with all local electrograms (egm) annotated at the last deflection (LD) was use for this methodology. Among the contemporary three-dimensional electroanatomical mapping systems, only EnSite system has several options for signal annotation, such as LD and “absolute dV/dt (DVDT)”, whereas other system applies “wavefront”, which annotate at the steepest negative dV/dt of the distal electrode with the guide of bipolar signals. The effect on annotation timing to the SR activation mapping is unclear.
Objective: To investigate the impact of annotation timing on SR activation mapping
Methods: Eleven patients (median age 66 years, 4 females, 4 ischemic and 7 non-ischemic cardiomyopathy) whom VT isthmus-related CSA identified on LD-based activation maps were included. CSA was defined as the area in which ≥ 70% narrowing in adjacent isochrone width. LD-based activation maps (left ventricular endocardial map in 3, epicardial map in 8) were reconstructed in which all egms being annotated at the DVDT using Turbo map function. Characteristics of LD- and DVDT-based activation maps were compared.
Results: All but one map (average points 3611/map) was obtained during intrinsic rhythm. Although total activation time was comparable (197 in LD vs. 173ms in DVDT, p = 0.11), activation time after QRS offset were significantly longer in LD maps (109 vs. 54ms, p < 0.01). The latest egms in DVDT maps overlapped with those of LD maps in 5 patients (45%). Although SR conduction propagated into the latest zone through the CSA in LD maps, no clear CSA was seen in DVDT maps.
Conclusion: Activation mapping at DVDT overlooked the conduction slowing during sinus rhythm. Annotation timing was felt to be crucial to fully utilize the functional substrate mapping.