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Integration of Three-Dimensional Scar Maps for Ventricular Tachycardia Ablation With Positron Emission Tomography-Computed Tomography

Timm Dickfeld, MD, PhD^_*,,1,_*, Peng Lei, MA^_*, Vasken Dilsizian, MD^_*, Jean Jeudy, MD^_*, Jun Dong, MD, PhD^,1, Apostolos Voudouris, MD^_*, Robert Peters, MD^_*, Magdi Saba, MD^_*, Raj Shekhar, PhD^_*, Stephen Shorofsky, MD, PhD^_*

^_* Division of Cardiology, University of Maryland, Baltimore, Maryland
Division of Cardiology, Johns Hopkins University, Baltimore, Maryland.

^_* Reprint requests and correspondence: Dr. Timm Dickfeld, Department of Cardiology, University of Maryland, 22 South Greene Street, Room N3W77, Baltimore, Maryland 21201. (Email: tdickfel{at}medicine.umaryland.edu).

Objectives: This study sought to assess the feasibility of deriving 3-dimensional (3D) scar maps from positron emission tomography (PET)/computed tomography (CT) hybrid imaging and to integrate those into clinical mapping systems to assist in ventricular tachycardia (VT) ablations.

Background: Ablation strategies for nonidiopathic VT are increasingly based on the anatomic information of the scar and its border zone. However, the current "gold standard" of voltage mapping is limited by its inability to accurately describe a complex 3D scar morphology, its imperfect spatial resolution, and prolonged procedure times.

Methods: Fourteen patients underwent PET/CT multimodality imaging before the VT ablation. We used PET/CT-derived scar maps to characterize myocardial scar using a 17-segment analysis and surface reconstruction. In 10 patients, reconstructed 3D metabolic scar maps were integrated into a clinical mapping system and compared with high-resolution voltage maps.

Results: A good correlation was found between the voltage maps and PET/CT-derived scar maps (r = 0.89; r < 0.05). In addition, 3D metabolic scar maps accurately displayed endocardial and epicardial surface and could be successfully integrated with a registration error of 3.7 ± 0.7 mm. A combination of visual alignment and surface registration was most accurate for myocardial scar accounting for 15% of the left ventricular surface. Scar size, location, and border zone accurately predicted high-resolution voltage map findings (r = 0.87; p < 0.05). Integrated scar maps revealed metabolically active channels within the myocardial scar not detected by voltage mapping and correctly predicted non-transmural scar despite normal endocardial voltage recordings. Areas of low voltage within wall segments displaying preserved metabolic activity were shown to be due to suboptimal catheter contact and prevented unnecessary ablation lesions.

Conclusions: We found that PET/CT fusion imaging is able to accurately assess left ventricular scar and its border zone. The integration of a 3D scar map into a clinical mapping system is feasible and may allow supplementary scar characterization that is not available from voltage maps. This technique could significantly facilitate substrate-based VT ablations.

Abbreviations and Acronyms   3D = 3-dimensional   CT = computed tomography   FDG = 18-fluorodeoxyglucose   LV = left ventricle/ventricular   MRI = magnetic resonance imaging   PET = positron emission tomography   SURF = surface shell registration   VT = ventricular tachycardia