Po-04-089 an unusual case of a right atrial appendage to posterior right ventricular outflow tract accessory pathway

Non-annular accessory pathways are rare to encounter in clinical practice. We present a rare case of a right atrial appendage to posterior right ventricular outflow tract accessory pathway in a patient with Wolf-Parkinson-White Syndrome. N/A A 26-year-old male with a structurally normal heart and Wolf-Parkinson-White syndrome was referred to our lab for electrophysiology study and catheter ablation. He had two prior electrophysiology studies and one unsuccessful ablation attempt of what was thought to be an anteroseptal accessory pathway. Baseline delta wave had an inferior axis and was negative in lead V1 (Figure 1A). Orthodromic atrioventricular re-entrant tachycardia was easily induced and occurred spontaneously during the procedure. Activation mapping during sinus rhythm showed earliest ventricular activation in the posterior right ventricular outflow tract (Figure 1F) distant from the tricuspid annulus. Limited ablation performed at this site did not alter accessory pathway conduction. Intracardiac echocardiographic imaging (Figure 1B) revealed the closest atrial tissue to this site was in the right atrial appendage. With atrial activation mapping during right ventricular pacing, the earliest atrial activation was in the right atrial appendage (Figure 1D) at a distance of 25.5 mm from the earliest ventricular signal (Figure 1E). The ventricular and atrial signals at this site were fused (Figure 1D). With radiofrequency ablation using 25 W initially and up-titrated to 40 W, ventricular pre-excitation was eliminated. The local EGM showed the initial fused atrial and ventricular signals had separated. After a waiting period greater than 30 minutes no further pre-excitation was observed. There was no VA conduction present after pathway elimination. Adenosine was given and resulted in complete AV block. Final ECG showed no pre-excitation (Figure 1C). At one month follow up he had no recurrence of palpitations or tachycardia. Non-annular accessory pathways are rare in clinical practice. Of the limited case reports on right atrial appendage to right ventricle accessory pathways in structurally normal hearts, most had prior failed ablation attempts. We suspect this is likely due to under recognition of non-annular pathways.