Case report: Mapping the uncommon: Right atrial appendage aneurysm unveiled through electrophysiological study

Abstract:
A right atrial appendage aneurysm (RAAA) is a rare anomaly, often linked to atrial arrhythmias. In this case, a 55-year-old man presented with recurrent supraventricular tachycardia. Electroanatomical mapping revealed a large sacculation in the right atrial appendage with four micro-reentry circuits around the anomaly. Radiofrequency ablation successfully terminated the tachycardias. Cardiac MRI confirmed the diagnosis of RAAA (Figure 1), underlining the importance of advanced mapping techniques in diagnosing structural anomalies and managing complex arrhythmias.

RAAA has fewer than 20 reported cases in the literature. Although rare, it can cause significant morbidity. Atrial tachycardias from the RAAA often occur in younger patients, recur frequently, and may persist, potentially leading to cardiomyopathy. Response to antiarrhythmic medication is generally poor.

In our case, the anomaly was found incidentally. The patient had a history of cavotricuspid isthmus (CTI) ablation for typical atrial flutter and was experiencing recurrent tachycardia. No prior family history of arrhythmias was known. The episodes, often captured by smartwatch ECG, occurred without clear triggers and lasted up to one hour. During tachycardia, his general condition worsened, leading to reduced physical activity.

Upon admission, the ECG showed sinus rhythm. Lab results including cardiac markers and inflammatory parameters were normal. Echocardiography showed no structural abnormalities except for a mildly dilated left atrium.

An electrophysiological study with 3D electroanatomical mapping (Rhythmia HDx™) was performed. After confirming the integrity of the previous CTI ablation line, atrial stimulation induced tachycardia with a variable cycle length (260–282 ms) and a “figure of eight” activation pattern (Figure 2).

Despite the unstable rhythm, a 3D right atrial map was constructed and suggested at least two concurrent tachycardias. A large sacculation was revealed in the lateral wall of the right atrium with no detectable voltage (Figure 3). Four micro-reentry circuits were located at the border of this structure. Ablation at the first circuit terminated the tachycardia. Substrate-based ablation at all four sites followed. Post-ablation testing confirmed non-inducibility of arrhythmias, even under isoproterenol.

Cardiac MRI further characterized the anomaly, confirming the presence of RAAA. This structure had not been detected on prior transthoracic echocardiography due to limited access to the right atrium.

The patient was discharged in stable condition. At follow-up, he reported no further episodes of tachycardia and good overall health.

Conclusion
This case illustrates the diagnostic and therapeutic value of 3D electroanatomical mapping in patients with atypical atrial tachycardia. It emphasizes the role of advanced imaging and mapping tools in identifying rare anatomical anomalies and guiding effective treatment.

References

1. Aryal MR et al. Right atrial appendage aneurysm: a systematic review. Echocardiography. 2014;31(4):534–9.
2. Luo L et al. Thoracoscopic Clamp RF Ablation on Atrial Tachycardia from RAAA after Catheter Ablation Failure. Front Cardiovasc Med. 2021.