High-Density Characterization of the Ventricular Electrical Substrate During Sinus Rhythm in Post–Myocardial Infarction Patients

OBJECTIVES The aim of this study was to characterize, during sinus rhythm, the electric activation abnormalities in post-myocardial infarction patients undergoing ablation of ventricular tachycardia (VT) in order to identify specific signatures of those abnormal etectrograms (EGMs).BACKGROUND In the setting of VT ablation, substrate characterization hinges on the identification of local abnormal ventricular activity (LAVA) and late potentials (LPs) that are considered to be related to the VT circuit.METHODS Patients scheduled for VT ablation underwent high-density ventricular substrate mapping. The substrate map during sinus rhythm was then compared with the activation maps of the clinical VT. Abnormal EGMs (LAVA and LPs) during sinus rhythm were characterized according to their configuration, duration, and amplitude and distinguished as belonging to bystander region or to the re-entrant circuit. Underlying electrophysiological mechanisms (wave-front collision, stow conduction) were identified on the activation maps and assigned to corresponding EGMs.RESULTS Ten patients satisfied the criteria to be enrolled in the study. A mean of 5 +/- 1 slow-conduction areas and 4 +/- 2 wave-front collisions were identified. LAVA was due to stow conduction in 60.5%, followed by wave-front collision (17.5%). LPs were caused by stow conduction in 52% of cases and by wave-front collision in 43% of cases. During sinus rhythm, entrance and exit sites were characterized by LAVA, white at the VT isthmus, only LPs were identified. Cutoff values of duration <24.5 ms (95% sensitivity and 99% specificity) and amplitude <0.14 mV (90% sensitivity and 48.1% specificity) discriminated those LPs belonging to the circuit from those playing a bystander rote.CONCLUSIONS In the setting of post-myocardial infarction cardiomyopathy, specific EGM signatures are expressions of distinct electrophysiological phenomena. LAVA and LPs may play a bystander or an active role in the VT circuit, but only LPs with tow amplitude and short duration predicted the VT isthmus. (C) 2020 by the American College of Cardiology Foundation.