|INTERESTING CASE REPORT
|Ahead of print publication
Double-Outlet Right Atrium – A Rare and Easily Misdiagnosed Entity
Kothandam Sivakumar, Sandeep Mohanty, Roy Varghese
Department of Pediatric Cardiology, Madras Medical Mission, Chennai, Tamil Nadu, India
|Date of Submission||24-Feb-2021|
|Date of Decision||15-Apr-2021|
|Date of Acceptance||16-Apr-2021|
|Date of Web Publication||09-Jun-2021|
Department of Pediatric Cardiology, Institute of Cardio Vascular Diseases, Madras Medical Mission, 4A Dr J J Nagar, Mogappair, Chennai - 600 037, Tamil Nadu
Source of Support: None, Conflict of Interest: None
Double-outlet right atrium (DORA) is a rare clinical entity associated with atrioventricular septal defects. Although it is easily correctable by surgery, it may be misdiagnosed during echocardiographic evaluation. Awareness and a thorough knowledge of this entity, its associations, echocardiographic appearances, surgical techniques, and its embryogenesis can alert the clinician to identify this rare but correctable condition. A young patient with DORA is described in this clinical report.
Keywords: Atrioventricular septal defect, common atrioventricular valve, deviated atrial septum, left superior vena cava, septum primum
|How to cite this URL:|
Sivakumar K, Mohanty S, Varghese R. Double-Outlet Right Atrium – A Rare and Easily Misdiagnosed Entity. J Indian Acad Echocardiogr Cardiovasc Imaging [Epub ahead of print] [cited 2021 Jul 23]. Available from: https://www.jiaecho.org/preprintarticle.asp?id=318103
| Introduction|| |
Double-outlet atrium is diagnosed when either of the two atria empty into both ventricles and the other atrium remains disconnected from the ventricular cavities. Double-outlet right atrium (DORA) associated with atrioventricular septal defect (AVSD) is characterized by extreme leftward deviation and mal-insertion of the atrial septum into the atrial wall, left and posterior to the mitral orifice. The left atrium empties through a defect in the deviated atrial septum and the right atrium drains directly into both ventricular chambers. It is sometimes misdiagnosed as a common atrium with a posterior recess or as a single atrium with abnormal left superior vena cava (LSVC) connection., This report describes the clinical presentation, imaging, surgical management, and embryological origin of DORA.
| Case Report|| |
A 5 year-old boy weighing 16.2 kg was referred for mild effort intolerance with a diagnosis of partial AVSD with obstructed cortriatriatum sinister. The somatic growth and pulse oximetry were normal with no features of specific syndromes. There was cardiomegaly, wide and fixed split of second heart sound, and a pulmonary flow systolic murmur. Cardiomegaly and pulmonary plethora were evident on chest X-ray. Prolonged PR interval, left axis deviation and counter-clockwise loop, consistent with AVSD was seen on electrocardiogram.
Echocardiogram showed normal situs with bilateral superior caval veins. The LSVC drained in to the right atrium through a roofed coronary sinus. The atrial septum was markedly deviated to the left and attached to the left lateral margin of the mitral annulus, committing the right atrium to both ventricles [Figure 1]. The small left atrium that received all the pulmonary veins had no direct connection to the ventricles except through a small atrial septal defect at the inferior part of the atrial septum immediately above the mitral valve orifice, that showed a cleft of the anterior leaflet, evident on three-dimensional echocardiogram [Figure 2]. The interatrial gradient across the restrictive septal defect was 8 mmHg between the posterior leftward smaller left atrium and large anterior right atrium. Mild tricuspid regurgitation predicted normal pulmonary artery pressures. The key echocardiographic finding was DORA, leftward fusion of atrial septum to the lateral mitral annulus, small restrictive atrial septal defect causing mild pulmonary venous hypertension, LSVC drainage close to the tricuspid annulus and selective streaming of left atrial blood through the atrial septal defect towards the mitral valve.
|Figure 1: Apical four chamber view echocardiogram (a) shows double outlet right atrium (RA), but the left atrium (LA) is disconnected from right ventricle (RV) and left ventricle (LV). An atrial septal defect (ASD) is shown by an arrow. A magnified view (b) shows lack of offset between the tricuspid and mitral attachments typical of atrioventricular septal defect. Color flow imaging (c) shows restrictive nature of ASD and favourable streaming (d) of the left atrial blood to mitral valve in diastole|
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|Figure 2: A view of three dimensional echocardiogram from the ventricular aspect of the atrioventricular valves (a) shows wide separation between the superior (SBL) and inferior (IBL) bridging leaflets and adequate size of left mural leaflet (LML) of mitral valve in diastole. At the beginning of systole, a cleft is identified in the zone of opposition between the bridging leaflets (b) directed towards the interventricular septum (IVS). The counterclockwise rotation of anterior (APM) and posterior (PPM) papillary muscles of left ventricles is typical for atrioventricular septal defect|
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Right atriotomy on cardiopulmonary bypass showed the atrial septum deviated posteriorly and to the left to insert to the lateral mitral annulus. There was a small secundum defect within this septum above the mitral valve. The pulmonary veins and the left atrial appendage were situated posterior to this malaligned septum. The mitral valve showed cleft of the anterior leaflet. The coronary sinus opened posteromedial to the mitral valve into the right atrium. Surgical findings confirmed DORA.
In order to cut back the atrial septum, the coronary sinus was deroofed by an incision that continued in the atrial septum up to the secundum defect thereby enlarging it [Figure 3]. A patch of bovine pericardium was then used to reroof the coronary sinus extending the coronary sinus into the area created for the future right atrium. A second autologous pericardial patch was then used to recreate the interatrial septum by suturing to the previous bovine pericardial patch to allow coronary sinus drainage into the new right atrium. Surgical recovery was uneventful. Echocardiogram on a 4-year follow-up showed separation of left and right atrium, mild mitral regurgitation, and normal ventricular function [Figure 4].
|Figure 3: After delineating the anatomy (a) during surgery, the coronary sinus (CS) was deroofed and the atrial septal defect (b) was enlarged to visualize all the left atrial structures. A bovine pericardial patch reroofed the coronary sinus to an area above the tricuspid valve (c) and finally atrial septation was completed with autologous pericardium (d)|
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|Figure 4: Postoperative apical echocardiographic view (a) shows atrial septation into left atrium (LA) and right atrium (RA) using a patch. Color Doppler (b) interrogation shows mild mitral regurgitation from left ventricle (LV) and mild tricuspid regurgitation from right ventricle (RV)|
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| Discussion|| |
DORA initially described in 1977 by Van Mierop is often misdiagnosed.,,, Three anatomical diagnostic requisites are (i) leftward deviation of the “true” atrial septum, (ii) a cephalic and posterior left atrium receiving the pulmonary veins that connect with a normal left atrial appendage, and (iii) two separate or a common atrioventricular valve. If these strict diagnostic criteria are not followed, a straddling atrioventricular valve that empties an atrium to both ventricles along with atresia of the other atrioventricular valve is misdiagnosed as DORA, as the second atrium is disconnected from the ventricular cavities.,, Syndromic association of DORA includes Ellis van Creveld, Raghib, and Turner syndrome.
A recent classification of DORA into those with malaligned atrial septum and those with malaligned ventricular septum further subdivides the former into patients with two separate atrioventricular valves- like our patient, and patients with a single atrioventricular valve. Those with malaligned ventricular septum are subdivided into patients with normal right ventricle and hypoplastic right ventricle. “Acquired DORA” occurs when a previous surgical ventricular septal defect patch dehiscence commits the right atrium to left ventricle associated with severe systolic regurgitation from left ventricle to right atrium.
Mild cyanosis is common in DORA due to right atrial blood emptying into the systemic left ventricle. Our patient lacked clinical cyanosis due to favorable streaming of the pulmonary venous blood through the atrial septal defect towards the mitral orifice. Additionally, a high pulmonary flow from a large left-to-right atrial shunt might have mitigated the hypoxia. As LSVC is seen in 75% of the patients with DORA, cyanosis may result from unroofed coronary sinus or proximity of coronary sinus orifice to the mitral valve.
The morphogenesis of DORA is attributed to an abnormal growth of septum primum in a leftward direction allowing the mesenchymal cap to fuse with the left lateral endocardial cushion rather than the superior and inferior bridging cushions., The presence of a common or two separate atrioventricular valves depend on the completeness of the division of the atrioventricular canal. Our patient had two well-formed atrioventricular valves. A frequent association is persistent LSVC that develops from the left horn of the sinus venosus.
Once the anatomy is recognized and drainage of LSVC is delineated, surgery is relatively easy in the presence of two atrioventricular valves [Figure 3]. The coronary sinus needs to be committed to the neo right atrium before atrial septation as in our patient. Common atrioventricular valve, coexistent defects such as tetralogy or double outlet right ventricle, severe atrioventricular valve regurgitation, or presence of three atrioventricular orifices challenge surgical repair.
| Conclusions|| |
Awareness about DORA as a clinical and echocardiographic entity will avoid its misdiagnosis during echocardiographic imaging. It is commonly associated with AVSDs and its identification helps to plan the surgical repair.
Consent to publish
Informed consent for the treatment and anonymous display of images in publications was obtained.
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.
Financial support and sponsorship
Conflicts of interest
K Sivakumar is an editorial board member of the Journal of The Indian Academy of Echocardiography & Cardiovascular Imaging. The article was subject to the journal's standard procedures, with peer review handled independently of this editor and their research groups.
There are no other conflicts of interest.
| References|| |
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]