1. Date of download: 6/18/2016 Copyright © The American College of Cardiology. All rights reserved. From: Entrainment mapping and radiofrequency catheter ablation of ventricular tachycardia in right ventricular dysplasia J Am Coll Cardiol. 1998;32(3):724-728. doi:10.1016/S0735-1097(98)00292-7 An example of an outer loop site is shown. Surface electrocardiogram leads I, II, III and V1 through V6 are shown on the top of the tracing with bipolar (RV 1-2) and distal, unipolar (RV U-1) recordings from the mapping catheter filtered at 30-500 Hz below. Sustained monomorphic VT with LBBB morphology, left axis and a cycle length of 440 ms is present. On the left-hand side of the slide the last three pacing stimuli of a stimulus train at a cycle length of 430 ms is shown. With pacing there is a change in the QRS morphology consistent with entrainment with QRS fusion. The post-pacing interval is 440 ms which is equal to the VT cycle length, consistent with a site within the reentry circuit. Figure Legend:

2. Date of download: 6/18/2016 Copyright © The American College of Cardiology. All rights reserved. From: Entrainment mapping and radiofrequency catheter ablation of ventricular tachycardia in right ventricular dysplasia J Am Coll Cardiol. 1998;32(3):724-728. doi:10.1016/S0735-1097(98)00292-7 A representation of reentry circuit site locations in the 5 patients is shown. The right ventricle is shown with the free wall dissected down; the septum and tricuspid valve are thus exposed. The exits are represented by circles, the central/proximal sites by squares, inner loop site are hexagons and outer loop sites by triangles. Solid symbols indicate sites where radiofrequency ablation terminated VT; termination at an unclassified site is indicated by an X. Reentry circuit sites are concentrated around the tricuspid annulus and in the ROVT. Figure Legend:

3. Date of download: 6/18/2016 Copyright © The American College of Cardiology. All rights reserved. From: Entrainment mapping and radiofrequency catheter ablation of ventricular tachycardia in right ventricular dysplasia J Am Coll Cardiol. 1998;32(3):724-728. doi:10.1016/S0735-1097(98)00292-7 (A) Entrainment at an exit site is shown. A VT with left bundle branch block inferior axis QRS configuration and cycle length of 345 ms is present. Pacing at a cycle length of 320 ms does not change the QRS morphology; VT is entrained with concealed fusion. The post-pacing interval is 345 ms, which is the same as the VT cycle length. The stimulus to QRS is 90 ms, which is less than 30% of the VT cycle length, consistent with an exit site. In (B) ablation at this site terminates the VT. Figure Legend:

4. Date of download: 6/18/2016 Copyright © The American College of Cardiology. All rights reserved. From: Entrainment mapping and radiofrequency catheter ablation of ventricular tachycardia in right ventricular dysplasia J Am Coll Cardiol. 1998;32(3):724-728. doi:10.1016/S0735-1097(98)00292-7 The entrainment site classification algorithm is shown. For the purpose of illustration, sites are related to a theoretical double loop reentry circuit shown at the bottom of the figure. Entrainment of ventricular tachycardia (VT) is performed; if there is a change in the QRS morphology (QRS fusion); and if the post-pacing interval (PPI) is >30 ms of the VT cycle length the site is a remote bystander; if the PPI is within 30 ms of the VT cycle length, the site is designated as an outer loop site. Those sites that have entrainment with concealed fusion with a PPI within 30 ms of the VT cycle length are further classified by the S-QRS duration as a percentage of the VT cycle length: exit sites have a S-QRS duration less than 30% of the VT cycle length, central/proximal sites have an S-QRS 30% to 70% of the tachycardia cycle length, and longer S-QRS intervals indicate inner loop sites. If there is entrainment with concealed fusion, but the PPI is greater than 30 ms of the VT cycle length the site is an adjacent bystander. Figure Legend: