Cor triatriatum sinister presenting in the fetus: beware of association with total anomalous pulmonary venous connection.

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A 36-year-old primigravida presented at the National Taiwan University Hospital at 33 weeks' gestation because of a suspected cardiac anomaly. Our initial evaluation revealed discordance between the size of ventricles and great arteries (Table 1). In addition, the left atrium (LA) was completely divided by an intra-atrial septum (Figure 1 and Videoclip S1). All four pulmonary veins (PV) drained correctly into the posterior chamber, but dilatation of the peripheral PV led us to suspect obstructed pulmonary venous return. Using color flow mapping, discernible blood flow across the septum was observed, from the posterior to the anterior chamber. Tubular coarctation of the aorta was identified based on findings of a small aortic arch and biphasic blood flow within the arch (Figure 2 and Videoclip S2). Cor triatriatum sinister was diagnosed, with suspicion of obstructed pulmonary venous return and tubular coarctation of the aorta. A 3050-g male was delivered by Cesarean section at 38 weeks' gestation because of recurrent decelerations in the fetal heart beat. At birth, the infant exhibited pallor and central cyanosis and was transferred to our neonatal intensive care unit. Postnatal computed tomography showed hypoplastic left heart syndrome (HLHS) with a small aortic arch and total anomalous pulmonary venous connection (TAPVC) via the vertical vein and left innominate vein (Figure 3). The infant did well after surgical correction of the atrial anomaly (i.e. creation of a common atrium which included the posterior chamber of the left atrium) and staged Norwood operations. Cor triatriatum develops at the beginning of the 5th week of gestation, when the primitive pulmonary vein appears as an outpouching from the LA that eventually makes contact with the primitive pulmonary venous plexus. Subsequently, the common PV is incorporated into the posterior wall of the LA, and the pulmonary venous plexus gradually loses its connection to the other venous systems1. Cor triatriatum sinister develops when partial partitioning occurs within the LA. Its embryonic basis remains controversial. The main theories involve faulty septation of the LA, malincorporation of common PV into the LA and entrapment of common PV by the left horn of the sinus venosus2. In most cases of cor triatriatum sinister, there is no restriction of pulmonary blood flow across the posterior and anterior chambers. Patients remain asymptomatic and usually are diagnosed incidentally during surgery, echocardiography or necropsy. However, cor triatriatum sinister has been reported to be associated with major congenital cardiac lesions in a pediatric population3. Although the association of cor triatriatum sinister with TAPVC is reported rarely, some have asserted that the actual prevalence should be considered to be higher, as cor triatriatum sinister and TAPVC share the same hypothetical mechanism during embryogenesis, namely, the malincorporation of common PV into the LA4. The occurrence of cor triatriatum sinister with TAPVC was categorized even as a specific subset (Type IB2) of cor triatriatum in a nomenclature database of congenital heart diseases5. In summary, we report a rare case of cor triatriatum sinister with tubular coarctation in which TAPVC and HLHS were diagnosed after birth. In this case, we did not detect TAPVC before birth, partly because of the narrow window for scanning at this advanced gestational age. Furthermore, since blood flow across the dividing membrane which separated the cor triatriatum sinister and the true LA was not limited at the time of the ultrasound examination, the vertical vein was not distended, which would have been seen on ultrasound examination. However, as pulmonary blood flow increased immediately after birth, the fenestration between cor triatriatum sinister and the true LA might not empty the oxygenated blood returning from the PV into the true LA efficiently. In this situation, the vertical vein would engorge and therefore TAPVC would be detected by computed tomography. In the present case, we speculate that the embryonic basis of cor triatriatum sinister contributed to the development of TAPVC, tubular coarctation of the aorta and HLHS. More cases would have to be analyzed to establish this speculation; however, if cor triatriatum sinister is diagnosed prenatally, it may be prudent to look for associated anomalies and to provide counseling for parents concerning possible associations that may not be ascertained prenatally. P. K. Yang*†, C. I. Chang‡, C. C. Lee§, M. W. Lin† and J. C. Shih† †Department of Obstetrics and Gynecology, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan; ‡Department of Surgery, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan; §Department of Obstetrics and Gynecology, Cathay Memorial Hospital, Taipei, Taiwan *Correspondence. (e-mail: [email protected]) Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.