• Abhishek Bhaskaran, Sachin Nayyar, Andreu Porta-Sánchez, Shouvik Haldar, Mahmoud Bokhari, Stéphane Massé, Timothy Liang, Nawazish Zehra, Talha Farid, Eugene Downar, and Kumaraswamy Nanthakumar.
• Division of Cardiology, Peter Munk Cardiac Centre, Toronto General Hospital, University Health Network, Toronto, Ontario, Canada.
• J. Cardiovasc. Electrophysiol. 2019 Apr 1; 30 (4): 520-527.

BackgroundNoninvasive electrocardiographic mapping of ventricular tachycardia (VT) and ablation using stereotactic radiotherapy was recently reported. This strategy does not directly evaluate the critical diastolic components and assumes that the epicardial exit site of VT subtends closely over the endocardial mid-diastolic isthmus.ObjectiveTo determine if the epicardial exit site of VT spatially corresponds to the critical diastolic components of ischemic scar-related VT.Materials And MethodsIntraoperative simultaneous endocardial and epicardial mapping were performed during VT using a 112-bipole endocardial balloon and 112-bipole epicardial sock array. In eight patients, nine VTs having entire diastolic circuit mapped were included in the study. The diastolic path and VT-exit sites (epicardial and endocardial) were determined.ResultsThe diastolic path was mapped in the endocardium for all nine VTs (median length, 50; interquartile range [IQR], 28 mm). The tachycardia cycle length ranged from 210-500 ms. The VT-exit site was early in the endocardium for six VTs and on the epicardium for three VTs. The mid-diastolic isthmus and endocardial exit site of the six endocardial VTs were spatially distant from their epicardial exit site by a median distance of 32 and 27 mm, respectively. For the three VTs with an early epicardial exit, the isthmus and endocardial exit sites were distant from the epicardial exit site by a median distance of 34 and 38 mm, respectively.ConclusionThe epicardial exit site and the mid-diastolic isthmus sites were spatially distant and discrepant. Surface electrocardiography (ECG)-derived strategy in identifying epicardial exit site to select noninvasive ablation targets is prone to identify epicardial exit sites and may not identify critical targets in ischemic scar VT.© 2019 Wiley Periodicals, Inc.

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