Case report
A 34-year-old woman, secundigravida, with a previous full-term natural childbirth – a boy with uncomplicated bicuspid aortic valve – showed a dilated superior caval vein at the prenatal ultrasound examination performed at 20 weeks of gestation. A fetal cardiac ultrasonography at 21 weeks confirmed the dilatation of the superior caval vein, which showed a diameter of 3.1 mm similar to that of the transverse aorta. The four pulmonary veins normally returned to the left atrium, ruling out an anomalous pulmonary venous connection. In the absence of other associated abnormalities, it was diagnosed as idiopathic dilatation of the superior caval vein.Reference Patel, Cobb, Rivera and Simpson 1, Reference Snider, Soifer and Silverman 2 At 30 weeks of gestation, the maximum dilatation was measured to be 8.1 mm, and the cardiac anatomy was normal. After a normal pregnancy, labour and vaginal delivery occurred without complications, and a 2.750-kg full-term female infant was born. The Apgar score was 8–9 at 1 and 5 minutes. A tender mass, not detected prenatally, was noted in the right submandibular and laterocervical region. The overlying skin appeared normal, and no obvious signs of compression were evident. The physical examination was otherwise normal. A postnatal cardiac ultrasonography confirmed the fusiform dilatation of the superior caval vein extending to the innominate vein, which showed a maximum diameter of 1.3 cm near the right atrium (Fig 1) where it assumed a spherical shape. The right atrium was normal in size. No other structural heart defects were identified, with the exception of a small patent ductus arteriosus that spontaneously closed in a short time. A Doppler ultrasound of the mass revealed a vascular anomaly characterised by cystic spaces with low vessel density and slow-flow arterial and venous waveforms on pulsed Doppler. The routine cranial ultrasonography was unremarkable. An MRI confirmed the presence of lymphatic malformation in the right laterocervical region dislocating the median structures of the neck (Fig 2). The mass reached the superior mediastinum up to the origin of the large vessels. There was no evident link between the lymphatic malformation and the dilated superior caval vein.
Figure 1 Saccular dilatation (asterisk) of the superior vena cava shown by transthoracic echocardiography. RA=right atrium.
Figure 2 MRI showing ( a ) aneurysm of the superior vena cava (asterisk) and ( b ) lymphatic malformation of the neck (arrow).
Discussion
The aetiology of superior caval vein aneurysms is unclear. It is believed that most of them are congenital without associated anomalies producing increased systemic venous return or elevation of systemic venous pressure.Reference Varma, Dharan and Ramachandran 3 Histo-pathological examination usually does not reveal any defect, but in some cases an inherent weakness in the wall of the vessel has been reported.Reference Ream and Giardina 4 , Reference Knight and Cancilla 5 In most of the cases, aneurysms of the superior caval vein are fusiform. Saccular aneurysms have been described only few times. In our case, the dilatation of the superior caval vein had a saccular appearance in proximity of the right atrium, and in the presence of this aspect we cannot rule out a primitive weakness of the vessel wall. An association with cystic hygroma has been described. Coexistence of superior caval vein aneurysm with hygroma could not be coincidental. In a series of 15 patients with mediastinal cystic hygroma reported by Joseph et al,Reference Joseph, Donaldson and Reynolds 6 eight of them also had venous aneurysms, with the majority involving the superior caval vein. Gorenstein et alReference Gorenstein, Katz and Rein 7 reported two cases of cystic hygroma in association with venous malformations. This association may be because of a common embryological origin of the venous and lymphatic systems.Reference Varma, Dharan and Ramachandran 3 , Reference Joseph, Donaldson and Reynolds 6 In newborn infants, a dilatation of the superior caval vein was rarely noted. In most cases, it occurred in association with an intracranial arteriovenous malformation of the vein of Galen. In these children, symptoms of congestive heart failure appear soon after birth. Two-dimensional echocardiograms usually show right atrial and right ventricular dilatation, the enlargement of the main pulmonary artery, and a marked enlargement of the superior caval vein owing to large volumes of blood under high pressure returning to the right heart.Reference Snider, Soifer and Silverman 2 In our case, the normal size of the right cardiac chambers and the absence of congestive heart failure signs led us to exclude the presence of high-pressure venous fluxes similar to those that may occur in arteriovenous malformations. To the best of our knowledge, in only three cases a prenatal diagnosis of superior caval vein aneurysms has been reported. In the first one,Reference Hirose, Yomo and Akiyama 8 the superior caval vein dilatation was noted in a fetus with an aneurysm of the vein of Galen. The fetal cardiac ultrasonography revealed cardiomegaly, and dilatation of the right atrium and superior caval vein. After birth, the neonate had congestive heart failure signs followed by respiratory arrest. A second caseReference Gorenstein, Katz and Rein 7 concerned a fetus with an ultrasound evidence of a neck mass detected prenatally. The fetal echocardiogram performed at 23 weeks showed a superior caval vein aneurysm in the absence of other structural heart defects. No clinical signs of heart failure were reported. The pathological specimen demonstrated a mixed lymphatic–venous malformation. The third caseReference Flores, Dangol and Strainic 9 regarded a dilatation of the superior caval vein discovered in a fetus by Doppler ultrasonography performed at 30 weeks of gestation. After birth, a fluctuating mass consisting in a large cystic hygroma of the right neck and the left axilla was found. Our case confirms the association of superior caval vein aneurysm with lymphatic malformations. We did demonstrate no direct drainage of the vascular malformation in the superior caval vein. However, we cannot rule out that in the presence of a hypothetical weakness in the wall of the superior caval vein even a low-pressure flow may contribute to the dilation of the vessel. Cervical lymphangiomas are very serious conditions for the risk of airway compression or massive bleeding.Reference Molino, Guillén and Peiró 10 As lymphatic malformations could not always be detected at the prenatal ultrasound, we suggest avoiding vaginal delivery in presence of a fetal diagnosis of the superior caval vein aneurysm, even without signs of right atrial and ventricular dilatation. In the presence of a lymphatic malformation, we strongly recommend excluding a coexisting venous aneurysm. Superior caval vein aneurysms are usually asymptomatic but they carry a theoretical high risk of complications, including pulmonary embolism and thrombosis. A close follow-up is therefore mandatory.
Acknowledgements
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This research received no specific grant from any funding agency or from commercial or not-for-profit sectors.
Conflicts of Interest
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Ethical standards
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
