9/8/2012 Disclosure-of-Relationship Utility of cardiac MRI - Research Grants, Consulting – for identifying the Arrhythmia Biosense-Webster Substrate during VT ablation Unlabeled Indications Timm Dickfeld, MD, PhD - Use of Gadolinium for MRI Scar Imaging Director of Electrophysiology, VA Baltimore Associate Professor of Medicine, University of Maryland MACIG (Maryland Arrhythmia and Cardiac Imaging Group) www.umm.edu/heart/macig Why Substrate Characterization? Anatomic Substrate of Reentrant Arrhythmias • In 193 patients LGE of 1.4% resulted in HR >7 for MACE Kwong R. et al. Circulation. 2006;113:2733 Inner Loop Entry Isthmus Exit Bystander Outer Loop De Bakker et al. Circulation 1988 Adapted: Stevenson W. Circulation. 1993;88:1647 4.3g myocardium = 1.4% LV mass 1
9/8/2012 Clinical Armentarium 2012 Anatomic Substrate of Reentrant Arrhythmias Hussein. AHA 2012. ICE MRI SPECT Dickfeld .Circ AE. 2011;4:172 Tian. JNM. 2012;53:894 CT PET LV Scar Imaging for Scar Characterization De Bakker et al. Circulation 1988 Dickfeld. JACC CV IM;1:73:2008 Tian. Circ AE 2010;3:496 Current Routing Use of Scar Imaging 1. None 38% 2. ICE Magnetic Resonance Imaging 3. CT 21% 4. MRI 17% 14% 5. PET 7% 3% 6. SPECT 0% 7. Several Modalities e E T I T T . R . n C C E C . I M P i o E l a N P d S o M l a r e v e S 2
9/8/2012 Results MRI: Near-Cellular SubstrateResolution - MRI: 3D Imaging Extraction - • LAD ligation Rat-infarct model • LGE ex-vivo 7T MRI RV Myocardium • Voxel: 50x50x50 µ m LV Endocardium • MRI/histoloy correlation (R 2 =0.96) • Ability to detect clefts SA MRI Slices 2-4 myocytes thick LV Epicardium LV Scar Schelbert et al. Circ Cardiovasc Imaging 2010;3;743 3D MRI Integration Correlation: MRI and Voltage DE MRI Voltage Map Registration Accuracy: 3.8±1.0mm 3
9/8/2012 MRI Scar and Voltage Mapping Correlation of Scar Transmurality and Voltage • Best voltage cut-off for MRI scar: - Bipolar voltage: 1.0-1.54mV 7 - Unipolar voltage: 4.46-6.52mV r = 0.72 Codreanu . JACC. 2008;52:839 Bipolar Voltage [mV] Desjardins. Heart Rhythm 2009;6:644 6 Dickfeld . Circ Arrhythm Electrophysiol. 2011;4:172 5 • Comparison MRI and Voltage Scar Area: 4 - MRI scar ~ <0.5mV scar area 3 Nakahara . Heart Rhythm 2011;8:1060 2 - MRI scar ~ <1.5mV scar+border zone area 1 Desjardins. Heart Rhythm 2009;6:644; Dickfeld . Circ Arrhythm Electrophysiol. 2011;4:172 - MRI scar slightly larger than 1.5mV area 0 Wijnmaalen . Eur Heart J. 2011;32:104 0 50 100 • Significant Mismatch: 1/3 of patients Scar Transmurality [%] Codreanu . JACC. 2008;52:839 Wijnmaalen et al . Eur Heart J. 2011;32:104 Dickfeld et al. Circ Arrhythm Electrophysiol. 2011;4:172 Mismatch: MRI Scar > Voltage Scar Mismatch: MRI Scar > Voltage Scar A A B B Endocardial layer of ~2mm normal myocardium masks • Endocardial scar <50% with bipolar voltage ≥ 1.5mV intramural scar (predominantly in septal location) Tian J et al. Heart Rhythm 2009; 6:825 Dickfeld et al. Circ Arrhythm Electrophysiol. 2011;4:172; Wijnmaalen et al.. Eur Heart J. 2011;32:104 Wijnmaalen et al. Eur Heart J. 2011;32:104 Dickfeld et al. Circ Arrhythm Electrophysiol. 2011;4:172; 4
9/8/2012 Mismatch: Voltage Scar > MRI Scar • Suboptimal Catheter Contact: - Frequently basal “pseudoscar” Codreanu A et al. JACC. 2008;52:839 Image-Guided VT Ablation Nakahara et al. Heart Rhythm 2011;8:1060 - Early registration algorithm (e.g. CartoSOUND) corrected 4.1±1.9% falsely low voltage points Dickfeld et al. Circ Arrhythm Electrophysiol. 2011;4:172 • Decreased MRI Sensitivity to detect patchy scar Nakahara et al. Heart Rhythm 2011;8:1060 • Limited Mapping Density: incorrect low voltage Desjardins et al. Heart Rhythm 2009;6:644 extrapolation MRI-Guided Ablation: Border Zone MRI-Guided Ablation: Border Zone - Pacemapping/Fractionation - 80-Sector Segmentation PM 2 PM 2 Pacemapping Guided by MRI Scar Pacemap Match Transmurality Display Reprojection of PM Site Dickfeld et al. Circ Arrhythm Electrophysiol. 2011;4:172 5
9/8/2012 MRI-Guided Ablation: Abnormal Substrate MRI-Guided Ablation: Substrate Identification 1 1 2 2 Surviving PM Substrate-Guided Mapping Pap. Muscle Match LV Voltage Map VT Dickfeld et al. Circ Arrhythm Electrophysiol. 2011;4:172 MRI-Guided Ablation: Midmyocardial Scar Successful RF Site Characteristics • Bipolar Voltage: 0.60-0.72mV (SD ≤ 0.9) Unipolar Voltage: 1.9-2.20mV (SD ≤ 2.1) • Fractionated Signals: 32-62% Diastolic Potentials: 23-66% • Transmurality: 60-68% (SD ≤ 38%) • Infarct core 17-71% Grey zone/periphery 29-83% • MRI LGE: 100% Mid- and Epicardial Scar with Preserved Endocardial Voltage Gupta et al. JACC CV Imaging. 2012;5:207 Perez-David E et al. J Am Coll Cardiol 2011;57:184 Desjardins et al. Heart Rhythm 2009;6:644 Dickfeld et al. Circ Arrhythm Electrophysiol. 2011;4:172 Wijnmaalen et al. . Eur Heart J. 2011;32:104 Dickfeld et al. Circ Arrhythm Electrophysiol. 2011;4:172 6
9/8/2012 VT Case #1 VT Case #1 • 76 yo pt with PHM of HTN, DM, new recurrent VT on Amio, CC in OSH: no CAD, EF 35% LBRI axis CL 420ms 12/12 PM Transition V 4 , no notching V 1/2 , QRS onset-nadir V1 <90ms NS VT inducible with burst pacing and PES (2ES) Winjmaalen et al. Circ Arrhythm Electrophysiol. 2011;4:486 MRI-Guided Ablation: Scar + Ablation VT Case #1 What is the VT mechanism? 43% Pre- 1. Reentrant VT RFA 30% 2. Automatic/triggered VT 27% 3. Don’t know Post RFA T . w V . . g o t i n n r t k a / r t c ’ t i n n t e a o Ablation Lesion extending into Scar Substrate m D e R o t u A Tian et al. Circ Arrhythm Electrophysiol. 2012.1;5(2):epub31 7
9/8/2012 ‘Grey Zone’ ‘Grey Zone’ - Mixture of Scar and Normal Myocardium - - Mixture of Scar and Normal Myocardium - • Grey zone correlated in ischemic patients with all-cause mortality, inducibility of MMVT and appropriate ICD shocks Yan A. et al. Circulation 2006;114;32 Schmidt A et al. Circulation. 2007;115:2006 Roes S. Circ Cardiovasc Imaging. 2009;2:183 De Bakker JM. Circ Arrhythm Electrophysiol 2010; 3:204 • Three different definitions: - Scar (>3SD), Grey Zone (2-3 SD), • Further refinement of binary concept (DE+/-) - Scar (>50% max SI), Grey Zone • Introduction of MRI scar core and periphery (>peak remote/<50%max SI) • Analogous to voltage-defined border zone - Scar (>50% max SI), Grey Zone (35-50% max SI) ‘Grey Zone’ Grey Zone – Human Studies - Mixture of Scar and Normal Myocardium - • 18 patients with ischemic CMP and MMVT • Ischemic swine model (n=17) compared with 18 matched patients • Inducible VT correlated with • Scar core (>3SD) and Grey zone (2-3SD) larger grey zone (25±10% vs. • Continuous grey zone corridors (88% vs. 33%, 13±5%) p<0.001) • Successful RFA of 22 VT, at • Voltage-map channels corresponded to Grey zone channels least one lesion in grey zone • Residual inducibility found with preserved grey zone Esthner H. Heart Rhythm 2011, doi: 10.1016 Perez-David E et al. J Am Coll Cardiol 2011;57:184 8
9/8/2012 Comparison of Three Grey Zone Algorithms Grey Zone – Human Studies • 10 patients with ischemic CMP and VT RFA FWHM NSD Mod. FWHM • Voltage as gold standard • Best MRI match with FWHM 60% and subendocardial half-wall thickness (scar r 2= 0.808; p<0.001 and BZ: r 2= 0.485; p=0.025) • Identified 81% of voltage-defined channels Grey Zone Scar=red Mass (n=41) BZ=green Mesubi AHA 2012 Andreu D. et al. Circ Arrhythm Electrophysiol. 2011;4:674 Resolution-Dependency of Grey Zone Comparison of Three Grey Zone Algorithms (partial volume effect) FWHM NSD Mod. FWHM • LAD-occlusion model in rats (n=8) - 55 ischemic ICD patients; Follow-up of 2.0 years • 7T MRI with voxel size of 50x50x50 µ m - 26% ventricular arrhythmias • Grey zone increase from 7 to 14% (p<0.01) Modified from DeHaan et al. Heart 2011;97:1951 Schelbert et al. Circ Cardiovasc Imaging 2010;3;743 9
9/8/2012 Virtual EP Study Diffusion Spectrum MRI Tractography 8 Week Swine LAD/LCX Occlusion Model (n=8) Simulation Non-contact Mapping • Excised paraffin- embedded rabbit hearts • LAD occlusion • 4.6T MRI • 515 diffusion- encoding gradient -3T MRI based scar/grey zone reconstruction vectors - GZ Model: +20% ADP, -50% conduction velocity - Predicted inducibility in 6/7 swine; 4 correct/2 opposite channel propagation Ng J et al. JACC 2012;60:423 Sosnovik D. Circ Cardiovasc Imaging. 2009;2: 206 Take-Home Points Thanks • MRI limitations in clinical practice (ICD, resolution etc) • Good correlation, some mismatch: • Jean Jeudi • Alan McMillan - <25% endocardial scar - ≥ 2mm viable endocardial myocardium • Charlie White • Carrol Fitzpatrick - catheter contact? • Jing Tian • Kathy Lynch • Facilitate substrate-guided ablation: • Ghada Ahmad • Debbie Nolan-Reily - Epi/endo approach • Steve Shorofsky • Erma White - Pacemap sites - Ablation sites? • Alejandro Jimenez • Correy Deans • Grey zone/DTI: Heterogenicity as Possible RF Target • Rich Kuk • Rao Gallupalli • Possible Future Application: Ablation Lesions Arrhythmic Modelling www.umm.edu/heart/macig 10
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