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Cor Triatriatum Dexter and Right Ventricular Hypoplasia in a Fetus

Cor triatriatum dexter is an extremely rare congenital anomaly of systemic venous valves that can lead to a wide spectrum of clinical symptoms and hemodynamic alterations. It has been hypothesized that failed regression of the venous valve may lead to fetal circulatory abnormalities and subsequent underdevelopment of right heart structures in utero. A case of cor triatriatum dexter with associated right ventricular and pulmonary valve hypoplasia is presented in a 22-week fetus diagnosed exclusively by echocardiography and confirmed via postmortem magnetic resonance imaging and gross inspection. A 35-year-old woman, gravida 7, para 1, presented at 22 weeks’ gestation for additional diagnostic evaluation after previous fetal sonographic evaluations revealed small right heart structures. Her medical history was unremarkable, with no history of medication, tobacco, or alcohol use. Extracardiac sonography revealed a normal nuchal thickness, biparietal diameter, and extremity length and no other organ or structural anomalies. Amniocentesis revealed a normal 46,XX karyotype, and fluorescence in situ hybridization screening results were negative for 22q11 deletion syndrome. First-trimester nuchal and serum screening results were also negative for aneuploidy. Dedicated fetal echocardiography revealed atrial situs solitus with normal superior and inferior vena cava connections to the right atrium. A left superior vena cava was observed connecting to a dilated coronary sinus. Concordant atrioventricular and ventriculoarterial connections were observed; however, a substantial ventricular size discrepancy was notable on initial evaluation, with a diminutive right ventricle in comparison to a normal-sized left ventricle (Figure 1A). Doppler interrogation of the ductus venosus revealed reversal of flow with atrial contraction. A patent foramen ovale was seen with right-to-left flow. Further evaluation revealed a linear membrane extending from the junction of the inferior vena cava and right atrium across the tricuspid valve orifice to the inferior limbus of the interatrial septum. The membrane prolapsed into the right ventricular cavity during diastole, resulting in interference with tricuspid inflow (Video 1). The tricuspid valve was hypoplastic with trivial tricuspid regurgitation (annulus measured 0.4 cm; normal, 0.5– 0.8 cm; z score, –3.32).1 The tricuspid valve inflow appeared substantially narrowed with an eccentric jet crossing from the right atrium to the hypoplastic right ventricle (Figure 1B). Pulsed wave Doppler interrogation of tricuspid valve inflow revealed a biphasic pattern with maximal Eand A-wave velocities of 0.4 and 0.5 m/s, respectively (Figure 1C). The pulmonary valve annulus was hypoplastic (0.25 cm; normal, 0.32–0.48 cm; z score, –3.74)1 but showed no evidence of abnormal valve thickening or flow acceleration on color or pulsed Doppler interrogation. Antegrade flow was shown across the right ventricular outflow tract, although a large patent ductus arteriosus was seen with bidirectional flow. Left heart structure dimensions were within normal limits for gestational age with normal left ventricular function and absence of left ventricular outflow tract obstruction. After full review of the echocardiogram and findings discussed above, the family was counseled regarding the likelihood of continued right ventricular hypoplasia through the remainder of the pregnancy. The possibility of adequate 2-ventricle physiologic structures was also discussed, although less likely on the basis of the ventricular size discrepancy at the second-trimester evaluation. Single-ventricle palliation was presented as the most likely surgical palliative strategy should right ventricular hypoplasia persist through the remainder of the pregnancy. The long-term complications associated with fontan circulation physiologic characteristics in patients with a single ventricle were also reviewed. Ultimately, the family decided to terminate the pregnancy, and an autopsy was performed. Before postmortem inspection of cardiac anatomy, additional imaging was obtained to aid in echocardiographic and pathologic correlation. Using a 7-T magnetic resonance imaging scanner, images of the specimen were obtained in room air without the aid of contrast media (Cliniscan, Bruker-Biospin; Siemens AG, Karlsruhe, Germany). High-resolution images were obtained, confirming the presence of right ventricular hypoplasia, a left superior vena cava–to–coronary sinus connection, and cor triatriatum dexter. Tricuspid valve patency was also confirmed, with annulus measurements identical to those measured on fetal echocardiography. Although appearing incomplete on limited sequential imaging, a thin membrane was seen extending from the entry of the inferior vena cava superiorly across the orifice of the tricuspid valve and attaching to the interatrial septum (Figure 1D). Autopsy revealed a 4.97-g heart (> 95th percentile for gestational age)2 with gross evidence of a ventricular size discrepancy and an apex leftward of the left anterior descending coronary artery. All anatomic findings were confirmed. In particular, careful right atrial dissection exposed a thin membrane extending from the medial rim of the inferior vena cava and right atrial connection across to the atrial septum, bridging the orifice of the tricuspid valve with variable thickness and irregularity (Figure 1E).