PMC4544642_01
a Twelve-lead ECG during sinus rhythm (SR), atrial tachycardia (AT-1, AT-2, AT-3; arrows) and atrial fibrillation (AF). b Fractionated electrocardiograms during focal atrial fibrillation originating from the interatrial septum near the region of the atrioventricular node slow pathway (MAP). HRA high right atrium, MAP mapping catheter, Cs coronary sinus, RVA right ventricular apex
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Fig1
His electrocardiogram showed a regular AT with narrow QRS (AT-1, Fig. 1a). AT-1 demonstrated focal activation from the right atrial (RA) septum. AT-1 was eliminated by radiofrequency (RF) ablation; however, AF initiation was noted after elimination of AT-1 (Fig. 1a). AF (Fig. 1b) was observed in the RA septum posterior to the region of the AV nodal slow pathway, which was very close to the successful ablation site for AT-1. After AF terminated during focal ablation at this site, another focal AT (AT-2, Fig. 1a) originated, with a different cycle length and a different P-wave morphology. AT-2 was identified in the left atrial (LA) septum just on the opposite side of the ablation site of AT-1. A third AT (AT-3) was additionally induced after AT-2 was eliminated using a transseptal approach for ablation (Fig. 1a).
Successful ablation sites (AT: green tag, AF: pink tag) in the atrial septum near the atrioventricular node on an electroanatomic map (a) and the corresponding short-axis computed tomography image (ZioM900; Ziosoft, Tokyo, Japan) (b). Color maps were overlaid on CT images to mark fat-density pixels with red color (fat defined based on Hounsfield units between -180 and 0). Intramural fat deposition is clearly demonstrated in the interatrial septum (red color). RA right atrium, LA left atrium, LAA left atrial appendage, Ao aorta, NCC noncoronary aortic cusp, Cs coronary sinus, LAO left anterior oblique
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Fig2
Electroanatomic mapping demonstrated the origins of these focal atrial tachyarrhythmias, which were located in the IAS close to the AVN (Fig. 2a). Contrast-enhanced computed tomography (CT) demonstrated the downward shift of the NCC and fat deposition within the anterior IAS close to the AVN (Fig. 2b).