EDITORIAL
Multielectrode Left Ventricular Mapping: Too Much or Not Enough? MATHEW D. HUTCHINSON, M.D. From the Division of Cardiology, Department of Medicine, University of Pennsylvania, Perelman School of Medicine, Philadelphia, Pennsylvania
Catheter ablation of ventricular arrhythmias remains fraught with significant challenges. Ventricular substrate mapping with single point acquisition is tedious and time consuming, particularly in patients with complex substrate distributions. Although global localization of arrhythmia substrate is necessary to understand the distribution of putative ventricular tachycardia (VT) circuits, it is often insufficient to effectively eliminate them in isolation. Enhancing procedural efficacy almost certainly requires a paradigm shift in the way we view mapping data. Our “color-centric” view of VT “substrate” is too often overly simplistic, ignoring important physiologic or functionally derived characteristics of the VT circuit. The experience with multielectrode mapping (MEM) in the human left ventricle remains largely anecdotal. The potential advantages of this technology over conventional point-to-point mapping are self-evident with respect to mapping time and density. Whether the data obtained with MEM will translate into improved clinical outcomes is purely speculative, and whatever benefit is realized will certainly require justification in light of the higher procedural cost incurred. The report from Thajudeen et al.1 in the current issue of this journal provides an important step forward in addressing the role of MEM in left ventricle (LV) mapping. The authors present a prospective cohort of five canines that underwent iatrogenic left anterior descending artery (LAD) infarction. All animals survived, and subsequently underwent cardiac magnetic resonance (MR) imaging and invasive electrophysiology (EP) testing at 4–6 months postinfarction. Gated contrast MR imaging was performed on a 3T scanner, and the resulting images were processed with commercially available software to produce 1-mm-thick 3D contours spanning the LV dimension. The signal intensity at each voxel Address for reprints: Mathew D. Hutchinson, M.D., Hospital of the University of Pennsylvania, 3400 Spruce Street, 9 Founders Pavilion, Philadelphia, PA 19104. Fax: 215-615-5235; e-mail: [email protected] Received February 5, 2015; accepted February 16, 2015. doi: 10.1111/pace.12616
(1 mm3 ) was determined using an automated algorithm, and expressed as a standard deviation (SD) from the intensity of the normal myocardium. Scar on delayed gadolinium enhancement (DGE) sequences was defined as >5 SD above normal myocardium; the transmural distribution of each scar region was determined. The subjects then underwent endocardial LV mapping using the IntellaMap OrionTM catheter and the RhythmiaTM electroanatomical mapping system (Boston Scientific, Marlborough, MA, USA). The mapping catheter has a basket profile with eight splines, each containing eight 0.4 mm2 electrodes spaced 2.5 mm apart. The maximal diameter of the equatorial section of the catheter can be adjusted from 3 mm to 22 mm. High-density MEM was performed in all five subjects (mean 7,754 points per subject). Approximately 40% of points acquired failed to satisfy predefined criteria of the mapping system (i.e., stability, morphology, or proximity to surface) and were automatically rejected. The bipolar and unipolar electrogram amplitudes from the remaining points were analyzed; bipolar voltage constraints (normal >2 mV and scar 2 mV) or abnormal (
Multielectrode Left Ventricular Mapping: Too Much or Not Enough? MATHEW D. HUTCHINSON, M.D. From the Division of Cardiology, Department of Medicine, University of Pennsylvania, Perelman School of Medicine, Philadelphia, Pennsylvania
Catheter ablation of ventricular arrhythmias remains fraught with significant challenges. Ventricular substrate mapping with single point acquisition is tedious and time consuming, particularly in patients with complex substrate distributions. Although global localization of arrhythmia substrate is necessary to understand the distribution of putative ventricular tachycardia (VT) circuits, it is often insufficient to effectively eliminate them in isolation. Enhancing procedural efficacy almost certainly requires a paradigm shift in the way we view mapping data. Our “color-centric” view of VT “substrate” is too often overly simplistic, ignoring important physiologic or functionally derived characteristics of the VT circuit. The experience with multielectrode mapping (MEM) in the human left ventricle remains largely anecdotal. The potential advantages of this technology over conventional point-to-point mapping are self-evident with respect to mapping time and density. Whether the data obtained with MEM will translate into improved clinical outcomes is purely speculative, and whatever benefit is realized will certainly require justification in light of the higher procedural cost incurred. The report from Thajudeen et al.1 in the current issue of this journal provides an important step forward in addressing the role of MEM in left ventricle (LV) mapping. The authors present a prospective cohort of five canines that underwent iatrogenic left anterior descending artery (LAD) infarction. All animals survived, and subsequently underwent cardiac magnetic resonance (MR) imaging and invasive electrophysiology (EP) testing at 4–6 months postinfarction. Gated contrast MR imaging was performed on a 3T scanner, and the resulting images were processed with commercially available software to produce 1-mm-thick 3D contours spanning the LV dimension. The signal intensity at each voxel Address for reprints: Mathew D. Hutchinson, M.D., Hospital of the University of Pennsylvania, 3400 Spruce Street, 9 Founders Pavilion, Philadelphia, PA 19104. Fax: 215-615-5235; e-mail: [email protected] Received February 5, 2015; accepted February 16, 2015. doi: 10.1111/pace.12616
(1 mm3 ) was determined using an automated algorithm, and expressed as a standard deviation (SD) from the intensity of the normal myocardium. Scar on delayed gadolinium enhancement (DGE) sequences was defined as >5 SD above normal myocardium; the transmural distribution of each scar region was determined. The subjects then underwent endocardial LV mapping using the IntellaMap OrionTM catheter and the RhythmiaTM electroanatomical mapping system (Boston Scientific, Marlborough, MA, USA). The mapping catheter has a basket profile with eight splines, each containing eight 0.4 mm2 electrodes spaced 2.5 mm apart. The maximal diameter of the equatorial section of the catheter can be adjusted from 3 mm to 22 mm. High-density MEM was performed in all five subjects (mean 7,754 points per subject). Approximately 40% of points acquired failed to satisfy predefined criteria of the mapping system (i.e., stability, morphology, or proximity to surface) and were automatically rejected. The bipolar and unipolar electrogram amplitudes from the remaining points were analyzed; bipolar voltage constraints (normal >2 mV and scar 2 mV) or abnormal (
