Abstract 734: Utilization of Positron Emission Tomography Perfusion/Metabolic Activities to Predict Electrophysiological Voltage Myocardium Scar in Patients Undergoing Ischemic Ventricular Tachycardia Ablation
Introduction: Image integration in commercially available 3D mapping systems is currently only used for surface reconstruction of the blood pool/endocardial interface and does not provide additional information about the myocardial scar substrate. Nuclear medicine techniques such as Rubidium-82(Rb) and 18-F fluorodeoxyglucose (FDG) positron emission tomography (PET) can help characterize myocardial substrate such as scar, normal and hibernating myocardium, which have been implicated in the arrhythmogenesis of ventricular arrhythmias. This study utilized the PET perfusion/metabolic activities to predict electrophysiological voltage scar.
Methods: Thirteen patients with ischemic cardiomyopathy underwent Rb/FDG PET imaging prior to VT ablation. The FDG segment with peak Rb perfusion was used as 100% to normalize FDG data. PET activities were classified as severe match (SMA, Rb<50%, FDG-Rb >10%), severe mismatch (SMI [hibernating], Rb<50%, FDG-Rb <10%), mild match (MMA, 50%<Rb<70%, FDG-Rb <10%), mild mismatch (MMI, 50%<Rb<70%, FDG-Rb >10%) and healthy (H, Rb>70%, FDG-Rb >10%). Voltage segments were defined by standard clinical criteria of scar (<0.5mV), BZ (0.5–1.5mV) and normal myocardium (>1.5mV). A 68-segment model developed by dividing each of the 17 AHA segments into 4 equally sized sub-regions was used to compare voltage and PET classifications.
Results: 48% (N=426) of segments were categorized into aforementioned voltage groups. Voltage values were significantly different between healthy and individual non-healthy segments (SMA, SMI, MMA, MMI, p<0.05). Using 0.5mV as the cut off value to define scar myocardium, ROC areas for Rb, FDG and FDG-Rb were 0.75±0.04, 0.67±0.04 and 0.53±0.05 respectively. Hibernating (SMI) myocardium segments have voltage features of scar (43%, N=6), BZ (14%, N=2) and normal (43%, N=6).
Conclusions: PET perfusion/metabolic activities are able to predict the electrophysiological voltage values and differentiate between tissue characteristics relevant for substrate-guided VT ablations in a detailed, high-segmental analysis. This supports the use of PET tissue characterization to facilitate substrate-guided VT ablations.
This research has received full or partial funding support from the American Heart Association, Mid-Atlantic Affiliate (Maryland, North Carolina, South Carolina, Virginia & Washington, DC).