Assessment of an ECG‐Based System for Localizing Ventricular Arrhythmias in Patients With Structural Heart Disease

Background We have previously developed an intraprocedural automatic arrhythmia‐origin localization (AAOL) system to identify idiopathic ventricular arrhythmia origins in real time using a 3‐lead ECG. The objective was to assess the localization accuracy of ventricular tachycardia (VT) exit and premature ventricular contraction (PVC) origin sites in patients with structural heart disease using the AAOL system. Methods and Results In retrospective and prospective case series studies, a total of 42 patients who underwent VT/PVC ablation in the setting of structural heart disease were recruited at 2 different centers. The AAOL system combines 120‐ms QRS integrals of 3 leads (III, V2, V6) with pace mapping to predict VT exit/PVC origin site and projects that site onto the patient‐specific electroanatomic mapping surface. VT exit/PVC origin sites were clinically identified by activation mapping and/or pace mapping. The localization error of the VT exit/PVC origin site was assessed by the distance between the clinically identified site and the estimated site. In the retrospective study of 19 patients with structural heart disease, the AAOL system achieved a mean localization accuracy of 6.5±2.6 mm for 25 induced VTs. In the prospective study with 23 patients, mean localization accuracy was 5.9±2.6 mm for 26 VT exit and PVC origin sites. There was no difference in mean localization error in epicardial sites compared with endocardial sites using the AAOL system (6.0 versus 5.8 mm, P =0.895). Conclusions The AAOL system achieved accurate localization of VT exit/PVC origin sites in patients with structural heart disease; its performance is superior to current systems, and thus, it promises to have potential clinical utility.

Novelties in cardiac pacing. Left bundle branch pacing, a step-by-step guide

Left bundle branch pacing (LBBP) technique is a new method for conduction system pacing that is useful for both bradyarrhythmia and heart failure indications. LBBP, while less physiological than His bundle pacing, offers several practical advantages. Namely, lower and stable pacing thresholds, good sensing of the intrinsic ventricular activity and easiness in localizing the pacing target. The LBBP method more often than His bundle pacing results in engagement of the conduction system distal to the area of the block. A step-by-step approach to LBBP was described. Attention was given to the following phases of the procedure: 1) localization of the target area on the septum, 2) the lead rotation technique with an interpretation of the lead responses (drill effect, screwdriver effect, entanglement effect), 3) methods for monitoring the lead depth in the septum to avoid perforation (fixation beats, continuous pace mapping, impedance), and 4) methods to differentiate between LBBP and left ventricular septal pacing.

Combined endo- and epicardial pace-mapping to localize ventricular tachycardia isthmus in ischaemic and non-ischaemic cardiomyopathy

Aims A high-density pace-mapping can depict an abrupt transition in paced QRS morphology from a poor to excellent match, unmasking the critical component of ventricular tachycardia (VT) isthmus from the entrance to exit. We sought to assess pace-mapping at multiple sites within the endo- and epicardial scars to identify the VT isthmus in patients with ischaemic (ICM) and non-ischaemic cardiomyopathy (NICM). Methods and results Colour-coded maps correlating to the percentage matches between 12-lead electrocardiograms during VT and pace-mapping [referred to as correlation score maps (CSMs)] were analysed. We studied 115 CSMs (80 endo- and 35 epicardial CSMs) in 37 patients (17 ICM, 20 NICM). The CSM with an abrupt change (AC) in pacemap score (AC-type) on the endocardium was more frequently observed in ICM than in NICM [11/39 (28%) vs. 1/41 (2%); P = 0.001]. Among 35 CSMs that were analysed by the combined endo- and epicardial mapping, 10 (29%) CSMs exhibited non-AC-type on the endocardium; however, AC-type was present on the opposite epicardium. Although 24 (69%) CSMs did not show AC-type on both the endocardium and epicardium, 16 of them had either an excellent (>90%) or poor (<0%) correlation score on either side, associated with isthmus exit or entrance, respectively. However, the remaining eight CSMs had neither excellent nor poor scores. Conclusion The CSM may provide electrophysiological information to localize the endo- and epicardial VT isthmus. The absence of AC-type CSM on the endocardium, which is frequently observed in NICM, appears to indicate the sub-epicardial or intramural course of the critical isthmus.

Selective Proximal Left Anterior Fascicle Pacemapping for Guiding narrow QRS Premature Ventricular Complex ablation from the Right Coronary Cusp

Premature ventricular complexes (PVC) ablation has increased over the past decades. The morphology of PVCs arising from left anterior fascicle (LAF) is typically a right bundle branch block-like morphology with an inferior axis showing a qR or qRs complex in the inferior leads and an rS or RS complex in leads I and aVL. We describe the case of a 38 years old woman with symptomatic, high burden PVCs, despite of beta blockers treatment. The PVC’s ECG morphology suggested an origin in the LAF. This case illustrates how ablation from the right coronary cusp for PVC arising from the LAF could be accurately guided by pace-mapping. At this location, pacing at different outputs can result in both a selective and a non-selective capture of the left anterior fascicle.

Magnetic resonance imaging of endocardial exits from epicardial ventricular tachycardia substrates in left ventricular nonischemic cardiomyopathy

Introduction: In patients with left ventricular (LV) nonischemic cardiomyopathy and monomorphic ventricular tachycardia (VT), midmyocardial and epicardial substrates are often involved but endocardial structures may also be affected. Delayed enhancement – magnetic resonance imaging (DE–MRI) was used to characterize the substrates of predominantly epicardial VT to improve identification of target sites for ablation. Methods and Results: 12 patients with LV nonischemic cardiomyopathy and monomorphic VT (prior myocarditis in 9) had a predominantly epicardial (n = 8) or epicardial-only DE-MRI substrate (n = 4). Modest-sized endocardial involvement in predominantly epicardial substrates was identified by DE-MRI in 8 patients. Mapping of 22 VTs was performed in 12 patients using an endo-epicardial approach in 6 patients and an endocardial-only approach in 6 patients. Endocardial VT reentry circuit exit sites as defined by entrainment and pace mapping criteria corresponded to endocardial breakthroughs from predominantly epicardial DE-MRI substrates in 7 patients. The endocardial VT exits were located at the ventricular base near the mitral annulus in 6 patients. Successful endocardial ablation of at least one VT was accomplished in 5 patients. Epicardial ablation as a part of an endo-epicardial approach or as epicardial-only ablation was performed in 6 patients and was successful in 4 patients. Conclusion: Endocardial breakthroughs from predominantly epicardial DE-MRI substrates are often located near the ventricular base in the perivalvular region and correlate with endocardial VT reentry circuit exit sites amenable to ablation.

Decrement Evoked Potential Mapping to Guide Ventricular Tachycardia Ablation: Elucidating the Functional Substrate

Empirical approaches to targeting the ventricular tachycardia (VT) substrate include mapping of late potentials, local abnormal electrogram, pace-mapping and homogenisation of the abnormal signals. These approaches do not try to differentiate between the passive or active role of local signals as the critical components of the VT circuit. By not considering the functional components, these approaches often view the substrate as a fixed anatomical barrier. Strategies to improve the success of VT ablation need to include the identification of critical functional substrate. Decrement-evoked potential (DeEP) mapping has been developed to elucidate this using an extra-stimulus added to a pacing drive train. With knowledge translation in mind, the authors detail the evolution of the DeEP concept by way of a study of simultaneous panoramic endocardial mapping in VT ablation; an in silico modelling study to demonstrate the factors influencing DeEPs; a multicentre VT ablation validation study; a practical approach to DeEP mapping; the potential utility of DeEPs to identify arrhythmogenic atrial substrate; and, finally, other functional mapping strategies.