Integration of radionuclide imaging of cardiac intrinsic nervous system with 3D electro-anatomical mapping for atrial fibrillation ablation

BACKGROUNG and OBJECTIVES: The intrinsic cardiac autonomic nervous system has been proposed to play an important role in atrial fibrillation (AF. Several studies have reported favorable outcomes by adding ganglionated plexi (GP) ablation to pulmonary vein isolation (PVI). I-123 mIBG SPECT imaging with a dedicated cardiac camera with solid state detectors (D-SPECT) detects sites with high tracer uptake corresponding to norepinephrine activity and can be merged with 3D reconstructions from either contrast enhanced CT (cCT) or cardiac magnetic imaging (CMR). We have assessed whether I-123 mIBG SPECT (MIBG) can facilitate localization of these GP's to guide AF ablation procedures. METHODS: The patients (pts) underwent I-123 mIBG nuclear imaging (D-SPECT, Spectrum-Dynamics) and co-registration of cCT or CMR. The focal uptake sites in the epicardial fat pads around the atria were documented and their activity was normalized to mediastinal activity. Subsequently, the merged data was imported into the 3D electro-anatomical mapping system (CARTO 3, Biosense Webster). A subset of pts underwent an AF ablation allowing an invasive confirmation of mIBG uptake sites using high frequency stimulation (HFS) to identify GP sites. Irrigated tip radiofrequency (RF) ablation for 30 sec (30 Watts, 17 ml/sec flow) with a contact force of > 10 g was performed on confirmed GPs until HFS was no longer positive. Finally standard antral pulmonary vein isolation was performed. All patients underwent close follow up with clinic examinations and sequential Holter recordings. RESULTS: 13 pts (mean age 57.5 years) underwent I-123 mIBG SPECT. They were injected with 372±6 MBq MBq of I-123 mIBG (radiation exposure of 2.4 mSv). The assessment of the location of the GPs revealed a very individual distribution with uncommon anatomical sites present in the majority of patients. Mean number of GPs was 5. Eight patients underwent an AF catheter ablation procedure. In this subgroup, HFS stimulation allowed identification of confined locations corresponding to GPs. No correlation was observed with CFAE areas. The mIBG guided mapping and ablation amounted to a median of 43 minutes. The median of EP fluoroscopy time was 8.18 minutes (equivalent dosage of 860 cGycm2). On a median follow up of 10.7 months 4/8 pts are still on antiarrhythmic medication and 7/8 pts are in SR. CONCLUSIONS: Registration of mIBG with cCT or CMR and electroanatomical mapping is feasible and facilitates localization of GP's. The so localized GPs are amenable to catheter ablation in patients with AF in addition to PVI. Further studies in large patient cohorts are necessary for confirm the effect of mIBG-guided GP ablation for different subtypes of AF