Figure 3.

A, B: Earliest atrial activation site assessed by the NavX system integrated with three-dimensional (3D) computed tomography (CT) in the left anterior oblique (A) and slightly cranial (B) views. C: Earliest ventricular activation site assessed by the NavX system integrated with 3D CT. Whereas a distinctive accessory pathway potential could be recorded at the neck of the coronary sinus (CS) aneurysm, the local ventricular activation was earlier deep within the aneurysm, where the unipolar electrogram confirmed a continuous P-QS morphology. The earliest ventricular activation likely spread toward the right inferoseptal wall near the tricuspid annulus but not the left ventricle (black arrow). The right and left panels show the local electrograms and surface electrocardiogram. The dotted line indicates the onset of the delta wave. D, E: CS venograms shown from the right anterior oblique (RAO) 30° (D) and left anterior oblique (LAO) 45° (E) views. White arrows indicate the CS aneurysm. F, G: Successful ablation catheter position shown in the RAO 30° (F) and LAO 45° (G) views. Of note, the successful ablation site was at the neck of the CS aneurysm, where a distinctive accessory pathway potential could be recorded. H: After the accessory pathway was eliminated, a sharp accessory pathway potential was documented after the ventricular potential (black arrows). This indicated that the accessory pathway could be eliminated at a more proximal site before it spread extensively toward the right ventricle. ABL = ablation catheter; HIS = His bundle; HRA = high right atrium; RVA = right ventricular apex.