Cardiac computed tomography angiographic identification of an uncommon right atrial outpouching in a complex congenital heart disease patient

Abstract

A 1-month-old infant had recurrent respiratory discomfort from birth. Transthoracic echocardiography revealed a significant ostium secundum atrial septal defect and a large ventricular septal defect (VSD). Subsequent-gated cardiac computerized tomographic angiography (CTA) showed a common atrio-VSD with single-ventricle physiology characterized by right ventricular morphology and preductal hypoplasia (coarctation) of the descending aorta. Furthermore, CTA revealed a smooth-walled, broad-based sac emanating from the anteroinferior right atrial wall, which collapses during systole without exerting pressure on neighboring cardiac structures, indicative of a congenital right atrial diverticulum. Right atrial diverticula are uncommon congenital malformations often identified incidentally and commonly linked with other structural cardiac conditions, such as septal defects.

INTRODUCTION

Congenital right atrial diverticulum is an uncommon, smooth-walled, and broad-based sac that contracts during systole without imposing a mass effect, distinguishing it from right atrial aneurysms (which are thin-walled and akinetic) and accessory atrial appendages.[1] The real frequency remains ambiguous, likely underestimated, due to its often asymptomatic nature and inadvertent detection. These diverticula frequently coexist with other congenital cardiac malformations, such as septal defects, a persisting left superior vena cava, and aortic hypoplasia. Typically asymptomatic, they may induce supraventricular arrhythmias and thrombotic problems. Electrocardiography-gated cardiac computerized tomography (CT) and magnetic resonance imaging (MRI) are crucial for precise distinction, integrating imaging characteristics and clinical context to inform therapy.

CASE REPORT

A 1-month-old infant presented with multiple episodes of respiratory distress since birth. An echocardiography revealed a large ostium secundum atrial septal defect and a large ventricular septal defect (VSD). Further cardiac computerized tomographic angiography (CTA) was conducted to assess the extracardiac anatomy, which demonstrated a large atrio VSD [black asterisk, Figure 1a] and a single ventricle of right ventricular morphology. Atrial situs was solitus, i.e., right atrium (RA) with its right atrial appendage were on the right side and left atrium and its left atrial appendage on the left side. No juxtaposition of atrial appendages was seen [Figure 1a-c]. In the extracardiac assessment, aortic arch hypoplasia with tubular narrowing of the preductal descending thoracic aorta was observed [whitle asterisk, Figure 1f]. A smooth-walled outpouching with a broad base was noted, arising from the anteroinferior wall of the RA, which collapsed during systole and showed no mass effect on adjacent cardiac chambers. All these findings were consistent with the atrial diverticulum [yellow asterisk, Figure 1b-e]. The child was managed conservatively with supportive medical therapy, as a definitive surgical correction was under consideration. Unfortunately, the child’s condition deteriorated, and he succumbed 4 days after the CT scan, before any surgical intervention could be undertaken.

Figure 1.

Oblique axial (a and c) and coronal (b) multiplanar reformatted and volume-rendered topography images show a large atrioventricular septal defect (black asterisk) between the right atrium (RA) and the left atrium and a single ventricle of right ventricle morphology. The right atrial appendage was seen pointing superiorly (b-e), and the left atrial appendage was pointing posteriorly and toward the left. A well-defined, smooth-walled outpouching with a broad base was noted, arising from the anteroinferior wall of the RA (Yellow asterisk). (f) show aortic arch hypoplasia (white asterisk) with coarctation of aorta (CoA). RV: Right ventricle, RA: Right atrium, RAA: Right atrial appendage, LA: Left atrium, VRT: Volume-rendered topography, MPR: Multiplanar reformatted, LAA: Left atrial appendage

DISCUSSION

A right atrial diverticulum is a rare congenital outpouching diagnosed incidentally.[1,2] The prevalence of right atrial diverticula is not well known, as these rare abnormalities are underreported. The embryological origin of these diverticula remains unclear. They are associated with other congenital cardiac malformations, such as VSD, persistent left superior vena cava, and hypertrophic cardiomyopathy.[3] In our case, they were associated with an atrio-VSD and a hypoplastic aortic arch with preductal coarctation of the aorta.

This atrial outpouching is usually asymptomatic, but it can be associated with atrial arrhythmia, chest pain, peripheral edema, shortness of breath, fatigue, and jugular engorgement. Supraventricular arrhythmia has been reported in patients, which is associated with a high risk of morbidity and mortality due to cardiac dysfunction and increased risk of stroke and heart failure.[4,5]

It can mimic other cardiac outpouchings, most commonly congenital aneurysms and accessory atrial appendages. These cardiac outpouchings often appear similar and are not well recognized by imaging, leading to uncertainty when identified. In addition, no established diagnostic criteria for conditions such as atrial aneurysms, accessory atrial appendages, and diverticula in existing studies and report further contribute to confusion.[1,2] However, a more definitive diagnosis can be made with the advancement and increasing use of gated CT and cardiac MRI.

Congenital atrial diverticula are the broad-based outpouchings with smooth contours and show no mass effect on adjacent cardiac structures. They show normal thickness and collapse during systole, whereas congenital atrial aneurysms typically have a wide neck and thin walls. They usually exert mass effect on adjacent cardiac chambers, lung parenchyma, and are usually akinetic on cine images. Finally, accessory atrial appendages are usually small in size (<1cm) and have a narrow neck and lobulated outline on imaging.[1,2,5]

The diagnosis of these atrial outpouchings should be based on the preponderance of imaging findings in combination with the clinical history, as no single feature is diagnostic and contradictory imaging findings may be present.[2]

A review of the literature indicates that congenital right atrial diverticulum is uncommon, with the majority of cases identified incidentally through imaging or autopsy. Diverticula are often linked to congenital cardiac anomalies, including septal defects, persistent left superior vena cava, and aortic arch abnormalities. A limited number of cases exhibit clinical symptoms, particularly supraventricular arrhythmias or conduction abnormalities, necessitating surgical or catheter-based intervention. Table 1 provides a summary of the key literature, highlighting comparative findings, presentation, and management strategies. Our case report contributes to the scarce literature on right atrial diverticulum, especially regarding a fatal outcome before the initiation of definitive surgical intervention.

Table 1.

Summary of right atrial diverticulum cases, associated anomalies, mode of detection, symptoms and interventions

Author/year		Associated cardiac anomalies		Mode of detection		Symptoms/morbidity		Intervention done
Binder et al., 2000[5]		Persistent left SVC, septal defects		Mostly incidental on autopsy/imaging		Rare arrhythmias		None/conservative
Shakerian and Mandegar 2020[4]		None reported		Symptomatic (palpitations, LBBB)		Arrhythmia, conduction defect		Surgical excision
Zhang et al., 2024[3]		None reported		Symptomatic (tachycardia)		Supraventricular tachycardia		Catheter ablation
Ufuk and Hazirolan 2023[1]		VSD, coarctation, LV hypertrophy		Mostly incidental on CT/MRI		Potential risk of thromboembolism		Observation in most
Hassani et al., 2023[2]		Septal defects, coronary sinus anomalies		Mostly incidental on cardiac CT		May mimic an aneurysm or cause diagnostic confusion		Conservative in most cases; surgery if needed

SVC: Superior vena cava, CT: Computed tomography, MRI: Magnetic resonance imaging, LV: Left ventricular, VSD: Ventricular septal defect, LBBB: Left bundle branch block

The optimal management approach remains uncertain and depends on the severity of complications, with options including surveillance, anticoagulation, catheter ablation, and surgical excision. Early identification of right atrial diverticula can provide valuable insight into arrhythmia risk and aid in ablation planning.[3]

CONCLUSION

Cardiac CTA may help assess subtle anatomic cardiac variants, and the characterization of these cardiac outpouchings is essential to ensure the optimal clinical management and therapeutic approaches.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the legal guardian has given his consent for images and other clinical information to be reported in the journal. The guardian understands that names and initials will not be published and due efforts will be made to conceal patient identity, but anonymity cannot be guaranteed.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.