Possibilities of single-photon emission computed tomography for the assessment of cardiac global and regional sympathetic activity in patients with atrial fibrillation

Aim. To evaluate global and regional sympathetic activity in patients with atrial fibrillation using 123I-metaiodbenzylguanidine (123I-MIBG) scintigraphy before and after catheter ablation. Methods. A total of 45 patients with paroxysmal and persistent atrial fibrillation (mean age, 55 ± 10 years; 44% women) followed up till catheter ablation were included in the study. All study participants underwent 123I-MIBG scintigraphy within 1-2 days before and 5-7 days after catheter ablation. The global myocardial sympathetic activity was estimated by calculating the ratio of 123I-MIBG uptake in the heart and mediastinum in the early and delayed phases (H/Me and H/Md), as well as the 123I-MIBG wash out rate in 4 h (WR). Regional sympathetic activity was estimated by semiquantitative analysis of the 123I-MIBG uptake in the myocardium of the left ventricle. Results. Baseline 123I-MIBG scintigraphy showed the difference between paroxysmal and persistent atrial fibrillation patients in WR only (19.2 ± 6.4 and 23.9 ± 7.2, respectively; p = 0.03). A statistically significant decrease of H/Md in average of 0.1 (95% confidence interval, 0.02-0.2; p = 0.02) was found in patients with paroxysmal atrial fibrillation, and a decrease of WR in average of 3.7% (95% confidence interval, -7% to -0.4%; p = 0.03) after catheter ablation. No statistically significant changes of H/Md and WR were found in patients with persistent atrial fibrillation after catheter ablation. The analysis of regional 123I-MIBG uptake in the left ventricular myocardium did not show any statistically significant changes in the regional sympathetic activity after catheter ablation compared with that at baseline. Conclusion. The differences in WR only were found between patients with paroxysmal and persistent atrial fibrillation. Significant changes in myocardial sympathetic activity after catheter ablation were found only in patients with paroxysmal atrial fibrillation, a finding that may be associated with a large number of active sympathetic nerve endings in the myocardium compared with patients with persistent atrial fibrillation.