Abstract 3096: Fusion Imaging with Positron Emission Tomography/Computer Tomography (PET/CT) to Guide Ventricular Tachycardia Ablations
Background: The latest generation of 3D mapping systems allows image integration to guide ablations for non-idiopathic ventricular tachycardia (VT). Currently, ventricular scar is defined by voltage mapping, which is limited by its spatial resolution, long procedure times, and the inability to describe complex scar anatomy with a surrogate voltage marker. Therefore, this study sought to investigate, if the combination of high-resolution CT (anatomic characterization) and 18-fluordeoxyglucose (FDG) PET (metabolic characterization) could accurately describe the scar morphology and myocardial metabolism to guide VT ablations.
Methods: 5 patients with ischemic cardiomyopathy and frequent VT underwent 18-FDG PET and contrast-enhanced CT prior to the VT ablation. Voltage mapping was performed using the conventional thresholds for scar (<0.5mV), diseased (0.5–1.5mV), and normal myocardium (>1.5mV). Areas of abnormal myocardium on contrast-enhanced CT images and FDG PET scans were analyzed in a 17-segment model as well as in a 3-D reconstruction and compared to the left ventricular voltage map.
Results: CT images identified abnormal, anatomical changes such as wall thinning, aneurysm, or myocardial calcification in all of the patients (spatial resolution <1mm). Areas of abnormal anatomy predicted areas of decreased voltage in more than 95% (p<0.05) and displayed a significant reduction of PET tracer uptake (range 20–50%). In the 17-segment analysis, FDG-PET and CT had a sensitivity and specificity of >85%, respectively to identify areas of abnormal voltage and the combination of both imaging techniques allowed the accurate prediction of scar, diseased, and normal myocardium (p<0.05). Several areas defined as scar by voltage map displayed normal anatomic appearance and persistent cellular metabolism, identifying areas possibly participating in reentrant circuits.
Conclusions: PET/CT allows a novel and comprehensive characterization of the ventricular scar for VT ablation. The combination of high-resolution myocardial anatomy and detailed regional cellular metabolism may facilitate voltage mapping, decrease procedure times, and provide new targets and treatment strategies for VT ablation.