Regional evaluation of cardiac sympathetic nervous activity in patients with paroxysmal atrial fibrillation using C-11 hydroxyephedrine PET/CT

Objectives Impaired cardiac sympathetic activity (CSA) is one of the mechanisms of paroxysmal atrial fibrillation (PAF). CSA decreased in the PAF patients reported by using MIBG scintigraphy. However, MIBG scintigraphy can not fully investigate at quantitative and regional evaluation. The aim of this study was to clarify whether PAF patients impaired CSA using C-11 hydroxyephedrine (HED) PET/CT.

Methods Nine PAF patients (65.8±7.9 years old) and 10 normal controls had HED PET/CT and O-15 H₂O PET. Valvular and ischemic heart disease patients were excluded. Whole and regional left ventricular (LV) retention index (RI) using 17-segment model were quantitatively evaluated. We evaluated RFnorm calculated with RI divided by myocardial blood flow. In regional analysis, 17 segments subdivided into 4 regions (anterior, septal, inferior and lateral wall) and compared anterior/inferior ratio between patients and normal controls. LV ejection fraction (EF) and left atrial dimension (LAD) were evaluated by echocardiography.

Results In PAF patients, LVEF was 62.0±12.1% and LAD was 40.7±5.9 mm. Myocardial blood flow did not differ between PAF patients and normal controls (P=1.00). Regional perfusion defect was not observed in PAF patients. PAF patients decreased whole LV RI compared with normal controls (0.069±0.026 vs. 0.157±0.029 /min, P<0.001) and RF_norm (0.099±0.053 vs. 0.203±0.045, P<0.001). There was no difference in RF_norm among 4 regions (P=0.96) with no differences in anterior/inferior ratio of RF_norm between PAF patients and normal controls (P=0.45).

Conclusions PAF patients homogenously impaired CSA even preserved LVEF. There was no regional CSA variability in PAF patients. Sympathetic activity impairment may be associated with arrhythmogenic substrate of AF.

Research Support None