A 67-year-old woman with history of hypertension and triple vessel coronary artery disease was sche duled for a coronary artery bypass grafting procedure. The preoperative investigations including the transthoracic echocardiogram (TTE) were all within normal limits. Written consent was obtained from the patient for publication of this report.
After induction of anesthesia, a S7-2 Omni transesophageal echocardiogram (TEE) probe (Philips, Bothell, WA) was inserted into the esophagus, and a comprehensive TEE examination was performed. On the midesophageal (ME) 4-chamber (4C) view, there appeared to be a double interatrial septum. Two septa that were oriented along the long axis of the heart, placed nearly parallel to one another, were seen between the 2 atria with a persistent midline echolucent space between them (Fig. 1). To examine the entity closer, a modified ME 4C view was obtained by turning the probe slightly to the right by centering the view on the right atrium (RA), adjusting the depth and sector width to focus on the interatrial septa, and then advancing or withdrawing the probe to scan the region of interest (Video 1, Supplemental Digital Content 1, http://links.lww.com/AA/A936). Next, the scanning plane was rotated by increasing the multiplane angle to 90° to obtain the ME bicaval view (Video 1, Supplemental Digital Content 1, http://links.lww.com/AA/A936). In this view, the septum primum (SP) (Fig. 2A), positioned toward the left atrium (LA), the accessory atrial septum (AAS) facing the RA, and the echolucent interatrial space (IAS) (Fig. 2B) between the 2 septa could be clearly identified. As a rule, the SP always faces the LA, and the more rightward septum that faces the RA is invariably the AAS. The SP was seen fluttering with phasic entry and exit of blood in and out of the IAS. The echolucent space was seen to expand during ventricular systole when atrial filling occurred, and partially collapse in diastole when blood from the space drained out into the LA and left ventricle. The AAS was seen to be relatively immobile. Adding a color flow Doppler window over the double atrial septum, while reducing depth and the velocity scale (≤20 cm/s), flow of blood could be detected in and out of the IAS. When freezing the live image and slowly reviewing the area using the trackball, a small patent foramen ovale (PFO) could be appreciated, located nearly at the center of the SP (Fig. 3A). An additional opening, accessory atrial septal fenestration (AAF) (Fig. 3B), was noticed at the inferior aspect of the SP, both on modified ME 4C and ME bicaval views. While shunting of blood could be detected between the IAS and the LA, both via the PFO and the AAF, no blood flow could be elicited between the IAS and the RA. Agitated saline contrast after the Valsalva maneuver and release was strictly confined to the RA and failed to show any communication between the RA, the IAS, and the LA (Video 2, Supplemental Digital Content 2, http://links.lww.com/AA/A937). Reducing the omniplane angle to 45° to 50° (ME aortic valve short-axis view) (Video 1, Supplemental Digital Content 1, http://links.lww.com/AA/A936) could also help view the double atrial septum from another angle.
Apart from the incidental double atrial septum detected by the intraoperative TEE, no other cardiac abnormality was evident. The patient’s history did not include any embolic events. Because of the incidental nature of the finding, the surgical team decided to leave the double atrial septum intact and advised the patient to be back for regular follow-up. Six months postoperatively, she remains asymptomatic and otherwise healthy.
Double interatrial septum is a visually distinct entity and may be distinguished from other relatively rare anatomic defects of the atrial septum, described in Table 1. Left atrial septal pouch,1 bifid atrial septal aneurysm,2 and aneurysm of the atrioventricular membranous septum3 are possible differential diagnoses. The presence of 2 parallel- oriented interatrial septa with a clear echolucent midline space between them that expands in systole and collapses in diastole periodically, particularly with a PFO identifiable on the SP, establishes the diagnosis of a double interatrial septum.
PFO is defined anatomically as the persistence of the fetal interatrial communication at the site of the embryonic ostium secundum, because of incomplete fusion of the SP and septum secundum (SS) with its opening on the fossa ovalis leading into the LA. Three-dimensional echocardiogram (Video 3, Supplemental Digital Content 3, http://links.lww.com/AA/A938) helps identify the tunnel between the SP and the SS. We differentiated between the PFO and the AAF by virtue of their anatomic features and location and as defined in previous literature.4
Two-dimensional views of particular value to assess the septum include the ME 4C, aortic valve short-axis, right ventricular inflow/outflow, and bicaval view. The modified bicaval view at 100° to 110° is also a key view to identify any sinus venosus atrial septal defect and abnormal pulmonary venous drainage. M mode can be used in the bicaval view to better show the motion, enlargement, and reduction of the IAS throughout the cardiac cycle.
Three-dimensional echocardiography allows improved visualization of anatomy and aids in confirming the diagnosis. Ideally, an en face 3D TEE view of the SP from the LA side can show the PFO as well as any accessory fenestration. Using 3D TTE from a subcostal view (Video 3, Supplemental Digital Content 3, http://links.lww.com/AA/A938), one can clearly visualize the tunnel between the SS and SP (PFO) opening into the LA, visualization of which using 2D is rarely possible. The presence of the tunnel between SS and SP identifies the opening as a PFO and not an accessory fenestration.
Double atrial septum is an extremely rare congenital cardiac anomaly.4 This entity has been reported in 7 cases with an age range of 16 to 91 years.1 While the majority of the reports was based on 2D TTE or TEE images, only 1 report4 described a 3D TTE subcostal view image. The presence of 2 interatrial septa is thought to result either from abnormal development of the SS, with failure of resorption of the superior portion of the SP in utero, or the additional septum is most likely to be a persistent left venous valve of the sinus venosus.4 Some authors describe this same anomaly where a third chamber is interposed between the LA and the RA, in the midline, as the type C cor triatriatum.5,6
Isolated double interatrial septum is an even rarer occurrence. The condition has been associated with transient ischemic attack resulting in unilateral hemiparesis.1 Thrombotic occlusion of the left circumflex artery due to a coronary embolus originating from the double interatrial septum has been reported.7 Stasis of blood within the IAS may result in thrombus formation and systemic embolization.7 The precise risk of thromboembolic events and the optimal management for prevention of any such event is unknown.1
It has also been associated with mitral atresia, pulmonary atresia, double outlet right ventricle, ventricular septal defect, coarctation, anomalies of pulmonary and systemic venous return, and hypoplastic left heart.4
In conclusion, double interatrial septum is a very rare congenital entity that has been associated with embolic stroke, coronary syndrome, and multiple congenital anomalies. Hence, an incidental finding of a double atrial septum should alert the intraoperative echocardiographer to carefully perform a detailed comprehensive TEE examination to exclude thrombus in the IAS as well as any additional congenital defects.
Clinician’s Key Teaching Points
By Kent H. Rehfeldt, MD, Massimiliano Meineri, MD, and Martin J. London, MD
- Double interatrial septum is a rare condition defined on a 2D transesophageal echocardiogram by the presence of an echolucent, interatrial space separating the septum primum on the left and an accessory atrial septum on the right. The interatrial space may communicate with the left atrium via a patent foramen ovale and demonstrate phasic systolic expansion and diastolic collapse (best seen using M-mode echo).
- Occurring in isolation or in association with a variety of congenital heart defects, double interatrial septum may increase the risk of left-sided embolic events due to stasis in the interatrial space.
- In this case, the 2 parallel septa and interatrial space were seen by scanning the interatrial septum at increasing multiplane angles from the midesophageal 4-chamber to midesophageal bicaval views along with use of color Doppler with a reduced aliasing velocity to demonstrate flow between the space and the left atrium via a patent foramen ovale and a fenestration located more inferiorly. An en face view obtained using 3D transesophageal echocardiogram of the atrial septum from the left side may aid in visualization of a patent foramen ovale and any other accessory fenestrations. Off-line cropping of a 3D data set perpendicular to the interatrial septum may facilitate detection of this abnormality. Because of the incidental, asymptomatic presentation in this older patient, no intervention was performed.
- There are other atrial septal anomalies, and they should be differentiated from double interatrial septum. An atrial septal pouch is a blind sac opening into either the left or the right atrium and lacks evidence of interatrial shunting. An aneurysm of the atrioventricular membranous septum presents as a cystic mass in the inferior right atrium with evidence of color flow communication from the left ventricle.
Name: Saikat Bandyopadhyay, DA, MD, FCCM, FTEE.
Contribution: This author helped design the study, conduct the study, analyze the data, and write the manuscript.
Attestation: Saikat Bandyopadhyay approved the final manuscript.
Name: Siddhartha Sathia, MBBS, MS, MCh.
Contribution: This author helped write the manuscript.
Attestation: Siddhartha Sathia approved the final manuscript.
Name: Manash Kumar Sanyal, MBBS.
Contribution: This author helped write the manuscript.
Attestation: Manash Kumar Sanyal approved the final manuscript.
Name: Kayapanda Mandana, MBBS, MS, MCh, FETCS.
Contribution: This author helped write the manuscript.
Attestation: Kayapanda Mandana approved the final manuscript.
This manuscript was handled by: Martin J. London, MD.
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