Characterization of the Electroanatomic Substrate in Cardiac Sarcoidosis: Correlation With Imaging Findings of Scar and Inflammation.

Abstract

This study sought to characterize the electroanatomic (EAM) substrate in patients with cardiac sarcoidosis (CS) and ventricular tachycardia and its relationship to imaging findings of inflammation and fibrosis. CS is characterized by coexistence of active inflammation and replacement fibrosis. A total of 42 patients with CS based on established criteria and ventricular tachycardia underwent high-density EAM mapping. Abnormal electrograms (EGM) were collected and independently classified as multicomponentfractionated, isolated, late, and split according to standard criteria and regardless of the peak-to-peak bipolar/unipolar voltage. A total of 29 patients (69%) underwent pre-procedural cardiac magnetic resonance (CMR) and positron emission tomography (PET)/computed tomography (CT). The distribution of EAMsubstrate was correlated with regions of late gadolinium enhancement (LGE) on CMR and increased 18F-fluorodeoxyglucose uptake on PET/CT. Of 21,451 bipolar and unipolar EGM, 4,073 (19%) were classified as abnormal with a predominant distribution in the basal perivalvular segments and interventricular septum. Using the standard bipolar (<1.5 mV) and unipolar (<8.3mV for left ventricle<5.5 mV for the right) voltage cutoff values, 40% and 22% of the abnormal EGM were located outside the EAM low-voltage areas, respectively. LGE was present in 26 of 29 patients (90%), whereas abnormal 18F-fluorodeoxyglucose uptake in 14 of 29 patients (48%) with imaging. Segments with abnormal EGM had more LGE-evident scar transmurality [median: 24% (interquartile range [IQR]: 4% to 40%) vs. median: 5%(IQR: 0% to 15%); p< 0.001] and lower metabolic activity (median: 20 g glucose [IQR: 14 g to 30 g] vs. median: 29 g glucose [IQR: 18 g to 39 g]; p< 0.001). Overall, the agreement between the presence of abnormal EGM was higher with the presence of LGE (κ= 0.51; p< 0.001) than with the presence of active inflammation (κ=-0.12; p= 0.003). In patients with CS and ventricular tachycardia, pre-procedural imaging with CMR and PET/CT can be useful in detecting EAM abnormalities that are potential targets for substrate ablation. Abnormal EGM were more likelylocated in segments with more scar transmurality (LGE) at CMR and a lower degree of inflammation on PET.