Discussion

This case highlights the importance of prenatal cardiac imaging in identifying rare structural heart anomalies. The detection of an aneurysm arising from the right ventricular outflow tract during a routine fetal echocardiogram is an exceptionally rare finding, along with its later association with neonatal arrhythmia. Together, these findings offer valuable clinical insights into a condition that remains largely unexplored in existing literature.

Antenatal detection of ventricular aneurysms was first described in 1990 by Gembruch et al. ^{Reference Gembruch, Steil, Redel and Hansmann5} where they described a large aneurysm arising from the left ventricular apex. Various case reports have been published since then describing such outpouchings. Most of the described cases involve outpouchings arising from the left ventricle. Congenital aneurysms of the right ventricular outflow tract are extremely uncommon. Most reported cases of right ventricular aneurysms or diverticula tend to arise from the free wall or apex and are often detected in older children or adults, sometimes as incidental findings, as in arrhythmogenic right ventricular dysplasia ^{Reference Chien, Lin and Lin6} or after surgical interventions. ^{Reference McElhinney7} In contrast, the detection of a structurally isolated right ventricular outflow tract aneurysm in utero, in a fetus with otherwise normal cardiac anatomy, is exceptionally rare.

Williams et al. in 2009 described a series of three cases with antenatally diagnosed right ventricle aneurysms with an uneventful postnatal course. ^{Reference Williams, Collardey, Treadwell and Owens8} Athiel et al. described another case series of three patients with antenatal detection of right ventricle outpouchings. ^{Reference Athiel, Barrois, Bault, Cohen, Leroy and Quibel9} Out of the three cases described, two pregnancies were uneventful and the postnatal period was stable, and in one case, termination of pregnancy was done in view of an associated large pericardial effusion. Another series of three cases was described by Zhong et al., describing outpouchings from right ventricle (outpouching from right ventricle lateral wall in one case, right ventricle apex in another case, and right ventricle posterior superior wall in the third case). ^{Reference Zhong, Chen, Zhang, Zhang, Liu and Ran10}

Prefumo et al. described two cases of antenatally detected ventricular aneurysm (aneurysm at left ventricular free wall in one case and at right ventricular apex in the other) with large pericardial effusions, one of which required antenatal pericardiocentesis. ^{Reference Prefumo, Bhide, Thilaganathan and Carvalho11}

The exact origin of such outpouchings and the exact difference between an aneurysm and a diverticulum remains unclear. Different criteria have been used to classify the two entities. Diverticula are distinguished by their restricted connection to the ventricle, the presence of myocardial fibres in their wall composition, and their ability to facilitate systolic contraction. Large connections, fibrotic tissue, and akinesia are characteristics of aneurysms. ^{Reference Ohlow1} The third entity, a ventricular pseudoaneurysm, occurs as a consequence of cardiac surgery or myocardial infarction. ^{Reference Inayat, Ghani and Riaz12} In our case, the aneurysm was akinetic, thin-walled, and in direct communication with the right ventricular outflow tract—features most consistent with a true congenital aneurysm rather than a diverticulum or pseudoaneurysm.

The antenatally detected ventricular outpouchings may remain stable or may be associated with serious complications, sometimes associated with fetal demise. Such complications may be electrical (e.g., premature ectopic complexes) or mechanical, as the ventricular rupture, as described by Bernasconi et al. ^{Reference Bernasconi, Delezoide, Menez, Vuillard, Oury and Azancot13} Many case reports have described an association with large pericardial effusions, which are usually not life-threatening but may require foetal pericardiocentesis. ^{Reference Williams, Collardey, Treadwell and Owens8}

In our case, although the aneurysm itself appeared stable and caused no obstruction or flow disturbance, it soon proved to be electrically active. By the third postnatal day, the neonate developed frequent ventricular premature complexes, with electrocardiographic features pointing towards a right ventricular outflow tract origin. The characteristic morphology—a left bundle branch block pattern with an inferior axis—is well established in idiopathic right ventricular outflow tract arrhythmias. ^{Reference Anderson, Kumar and Parameswaran4} The arrhythmia emerged in the neonatal period, in the setting of a structurally abnormal but otherwise haemodynamically silent outflow tract.

The presence of such an arrhythmia raises several important considerations. While idiopathic right ventricular outflow tract arrhythmias are often benign and self-limiting in adults, little knowledge is available in neonates to date regarding the future implications. In our patient, the arrhythmia caused haemodynamic instability, and an identifiable structural substrate prompted early intervention and resolution.

Amiodarone was chosen as first-line therapy, given its well-documented efficacy in managing neonatal ventricular arrhythmias. ^{Reference Batra, Silka and Borquez14} Within 6 hours of initiating intravenous therapy, the ventricular premature complexes resolved completely. The infant transitioned smoothly to oral therapy, with no signs of bradycardia or QT prolongation, and remained clinically stable during follow-up. Thyroid and hepatic function remained within acceptable limits.

At this point, the long-term outlook remains cautiously optimistic, but surveillance will be crucial. Even though the aneurysm has remained stable in size, the potential for future complications—including thrombus formation, aneurysm growth, or recurrence of arrhythmia—cannot be dismissed. The absence of clear guidelines for managing isolated congenital right ventricular outflow tract aneurysms further underscores the need for individualised follow-up strategies.

In essence, this case adds to the small but growing body of evidence that fetal right ventricular outflow tract aneurysms, although rare, may not be as clinically silent as previously believed. Their arrhythmogenic potential should prompt close rhythm surveillance and timely management. Timely diagnosis, thoughtful therapy, and vigilant follow-up can lead to favourable outcomes—even in the face of such diagnostic uncertainty.