The effects of electromagnetic interference generated by catheter ablation on pacemaker function were evaluated in vitro. With the pacemaker, atrial & ventricular leads, and counter electrode plate placed in an acrylic water tank, the ablation catheter was gradually brought closer to the pacemaker starting first at a distance of 10cm. Electrodes were placed near the pacemaker, atrial and ventricular leads, and counter electrode plate in order to observe the electrogram（EGM）, and a polygraph was then used to measure the EGM. With electric current flowing near the leads, pacemaker operating mode differences were observed in the polarity switching function and the safety pacing function depending on the manufacturer. Some models interpreted electric interference when electric current from the ablation catheter flowed near the lead. Many models switched to dual atrial/ventricle pacing, and pacing potential was also confirmed near the counter electrode plate as well as the generator. Dual atrial/ventricular pacing was observed in some models by bringing a non-charged ablation catheter closer to the pacemaker generator. In conclusion, implanted pacemakers frequently exhibit transient, unpredictable responses to RF energy application. Since differences in the response to electromagnetic interference were measured in each manufacturer’s pacemaker, it is important to understand these differences before surgery and implantation in order to make the necessary mode settings and changes based on the situation.

In patients with atrial fibrillation（AF）, left atrial appendage filling defect（LAAFD）is sometimes seen only at the early phase of dual phase enhanced cardiac computed tomography（ECCT）. In the present study, we compared differences in clinical characteristics between AF patients with（LAAFD+ group, n = 16）or without（LAAFD- group, n = 48）LAAFD. Left atrial volume（LAV）, left ventricular systolic/diastolic function by transthoracic echocardiography, spontaneous echo contrast（SEC）, left atrial appendage（LAA）flow and Pulse Doppler velocity of tissue Doppler imaging（PWV-TDI）by transesophageal echocardiography, and the ratio of Hounsfield unit of LAA and ascending aorta（LAA/AA HU ratio）both at early and delayed phases of ECCT were evaluated. In the LAAFD+ group, proportion of persistent AF, plasma BNP value, LAV were higher, and LAA flow and PWV-TDI were lower than for the LAAFD- group. In multivariate logistic regression analysis, LAA flow and PWV-TDI at LAA orifice were significant predictors of LAAFD. The LAA/AA HU ratio at the early phase of ECCT was significantly lower in patients with dense SEC than in patients without SEC. The presence of LAAFD was influenced by LAA function and was frequently coexistent with dense SEC. Therefore, the presence of LAAFD might be an indirect risk of stroke.