RT Journal Article SR Electronic T1 Ventricular Tachycardia (VT) Substrate Characteristics: Insights from Multimodality Structural and Functional Imaging of the VT Substrate Using Cardiac MRI Scar, 123I-Metaiodobenzylguanidine SPECT Innervation, and Bipolar Voltage JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 79 OP 85 DO 10.2967/jnumed.118.211698 VO 60 IS 1 A1 Hasan Imanli A1 Kiddy L. Ume A1 Jean Jeudy A1 Tamunoinemi Bob-Manuel A1 Mark F. Smith A1 Wengen Chen A1 Mohammed Abdulghani A1 Yousra Ghzally A1 Jagat Bandhu Mahat A1 Refael Itah A1 Alejandro Restrepo A1 Vincent Y. See A1 Stephen Shorofsky A1 Vasken Dilsizian A1 Timm Dickfeld YR 2019 UL http://jnm.snmjournals.org/content/60/1/79.abstract AB Postischemic adaptation results in characteristic myocardial structural and functional changes in the ventricular tachycardia (VT) substrate. The aim of this study was to compare myocardial structural and functional adaptations (late gadolinium enhancement/abnormal innervation) with detailed VT mapping data to identify regional heterogeneities in postischemic changes. Methods: Fifteen patients with ischemic cardiomyopathy and drug-refractory VT underwent late gadolinium enhancement cardiac MRI (CMR), 123I-metaiodobenzylguanidine SPECT, and high-resolution bipolar voltage mapping to assess fibrosis (>3 SDs), abnormal innervation (<50% tracer uptake), and low-voltage area (<1.5 mV), respectively. Three-dimensional reconstructed CMR/123I-metaiodobenzylguanidine models were coregistered for further comparison. Results: Postischemic structural and functional adaptations in all 3 categories were similar in size (reported as median [quartile 1–quartile 3]: CMR scar, 46.1 cm2 [33.1–86.9 cm2]; abnormal innervation, 47.8 cm2 [40.5–68.1 cm2]; and low-voltage area, 29.5 cm2 [24.5–102.6 cm2]; P > 0.05). However, any single modality underestimated the total VT substrate area defined as abnormal in at least 1 of the 3 modalities (76.0 cm2 [57.9–143.2 cm2]; P < 0.001). Within the total VT substrate area, regions abnormal in all 3 modalities were most common (25.2%). However, significant parts of the VT substrate had undergone heterogeneous adaptation (abnormal in <3 modalities); the most common categories were “abnormal innervation only” (18.2%), “CMR scar plus abnormal innervation only” (14.9%), and “CMR scar only” (14.6%). All 14 VT channel/exit sites (0.88 ± 0.74 mV) were localized to myocardium demonstrating CMR scar and abnormal innervation. This specific tissue category accounted for 68.3% of the CMR scar and 31.2% of the total abnormal postischemic VT substrate area. Conclusion: Structural and functional imaging demonstrated regional heterogeneities in the postischemic VT substrate not appreciated by any single modality alone. The coexistence of abnormal innervation and CMR scar may identify a particularly “proarrhythmic” adaptation and may represent a potential novel target for VT ablation.