Abstract 376: High Washout Rate of Iodine-123-Metaiodobenzylguanidine Imaging Predicts Late Recurrence of Atrial Fibrillation Following Radiofrequency Catheter Ablation
Background: Despite technical refinements in the catheter ablation of atrial fibrillation (AF) and its long-term success, AF recurrences after the procedure remain an important problem. The autonomic nervous system is known to contribute to AF recurrence after the ablation, but its precise role remains controversial. Iodine-123-metaiodobenzylguanidine (123I-MIBG), an analogue of norepinephrine, can be used to assess the cardiac sympathetic nervous function.
Methods: This study included 88 consecutive patients with paroxysmal (n=48 [55%]) or persistent (n=40 [45%]) AF (mean age 58±10 years) who underwent an electrical isolation of all pulmonary veins (PVs) by the extensive PV isolation technique and a linear ablation at the cavo-tricuspid isthmus. 123I-MIBG scintigraphy was performed before discharge during a stable condition. Anterior planar imaging was obtained at 30 min and 180 min and the washout rate of the 123I-MIBG from 30 to 180 min was calculated.
Results: There was no difference between the patients with an AF-recurrence (n=25 [28%]) and those without (n=63 [72%]) in terms of the age, gender, BNP level or proportion of patients with antiarrhythmic drugs. In the parameters of the 123I-MIBG imaging, the heart to mediastinum ratio of the 123I-MIBG uptake at 30 min (H/M 30 min) and 180 min (H/M 180 min) did not differ between the patients with an AF-recurrence and those without (H/M 30 min: 1.81 vs. 1.81, p=0.88; H/M 180 min: 1.91 vs. 1.98, p=0.36, respectively). However, the washout rate of the 123I-MIBG was faster in the patients with an AF-recurrence (29.2%) than in those without (23.8%, p=0.003). Univariate predictors of an AF-recurrence were the duration of an AF history, left atrial dimension, and washout rate of the 123I-MIBG. Only the 123I-MIBG washout rate was a multivariate predictor of an AF-recurrence (Hazard ratio: 1.6, 95% confidence interval of the hazard ratio: 1.004 to 1.125, p=0.037).
Conclusions: Excessive sympathetic nervous activation may be one of the mechanisms of AF recurrences. Evaluation of the cardiac nerve activity using 123I-MIBG scintigraphy shortly after the AF ablation may be a promising tool to predict the patient’s outcome.