Anomalies of systemic venous return are generally of little haemodynamic consequence. The most commonly encountered anomaly, in presence of a right superior caval vein, is a persistent left superior caval vein draining into the right atrium or into the coronary sinus. In up to one-tenth of cases, however, the persistent left superior caval vein empties into the left atrium,1–3 albeit most often in presence of a right superior caval vein, which empties into the right atrium. Isolated drainage of a left superior caval vein into the left atrium, in absence of either another congenital cardiac malformation or a right superior caval vein, is much rarer.3–7 In this report, we present a new case, describing its management and clinical evolution.
Case report
The patient was a 15-month-old boy. On neonatal examination, an imperforated anus and urethrorectal fistula were noted, for which a temporary left iliac colostomy was performed. On the second day of life, he was noted to be cyanotic, with transcutaneous oxymetry of 88%, which remained fixed despite administration of oxygen. Except for a praecordial systolic murmur, of grade one from six, the remainder of the cardio-respiratory examination was normal, as was the electrocardiogram. A frontal chest radiograph showed mild cardiomegaly, with a cardio-thoracic index of 0.59. On echocardiography, a small subaortic ventricular septal defect was present, which was partially occluded by an aneurysm of the membranous septum, along with an aneurysm of the inter-atrial septum with patency of the oval foramen and a left-to-right shunt. While the inferior caval vein was shown to be normally connected with the right atrium, the superior caval vein was not identified. A contrast injection of micro-bubbles in 5% glucose from the left superior extremity, demonstrated the presence of exclusive drainage to the left atrium, followed by opacification of the right atrium. Computed tomography confirmed the presence of anomalous systemic venous return from the brachio-cephalic venous system into the superior caval vein, which emptied into the left atrium, near its appendage (Fig. 1). The infant had a normal caryotype, and abdominal echography showed no evidence of mirror-imaged visceral arrangement.
Figure 1. The three-dimensional reconstruction computed tomographic scan shows the brachio-cephalic venous trunk (BCVT), the left jugular vein (LJV), the left subclavian vein (LSSCV) draining into the left superior caval vein (LSCV). The left superior caval vein is connected at the superior part of the left atrium near the left appendage. Abbreviations: LV: left ventricle; Ao: aorta.
The child was asymptomatic and developed normally. With the spontaneous closure of the ventricular septal defect, the transcutaneous arterial saturation gradually fell, reaching 72% at 6 months of age. Cardiac catheterization, performed at 8 months of age, revealed normal intrapulmonary pressures and a structurally normal heart. A catheter advanced from the right atrium through the septal defect reached a vessel located in the high posterior region of the left atrium. Contrast angiography showed the presence of a duplicated brachio-cephalic trunk, and all systemic venous return via a solitary superior caval vein connected to the roof of the left atrium (Fig. 2). The pulmonary venous return was normal.
Figure 2. The radio-opaque catheter is entering the right atrium and the left atrium via a patent oval foramen, and then the left superior caval vein. Angiography shows the brachio-cephalic venous trunk and the left superior caval vein draining into the superior part of the left atrium near the left appendage.
At the age of 10 months, the child underwent closure of the urethro-rectal fistula, with opening of the rectal cavity to the skin surface, and restoration of intestinal continuity. At the age of 1 year, because of severe hypoxaemia, and of the risks associated with right-to-left shunting, the child underwent surgical correction of the anomalous systemic venous return. Intraoperatively, the right superior caval vein was found to be represented by a fibrous cord. The left superior caval vein was connected to the left atrium near the appendage. In absence of an atrial septal defect, a right atriotomy was performed, and the aneurysmal membrane of the oval fossa and the superior portion of the interatrial septum were resected. A Dacron patch was sutured in the high left atrium, around the mouth of the left superior caval vein, toward and onto the edges of the interatrial septum, tunnelling the left superior caval vein into the right atrium.
The child made an uneventful postoperative recovery and, 3 months later, the transcutaneous arterial oxygen saturation had risen to 100%, and echocardiographic interrogation revealed non-turbulent blood flowing through the patch. Six months after the operation, echocardiography revealed the presence of narrowing inside the intra-atrial patch, and the development of a mild gradient (11 millimeter of mercury; mean is equal to 5 millimeter of mercury) by Doppler examination. Since the child had remained asymptomatic, we chose to continue following him by echocardiography and to postpone the performance of a percutaneous dilation procedure, if it became necessary.
Discussion
The functional symptomatology produced by a superior caval vein draining to the left atrium consists mostly of dyspnoea due to right-to-left shunting, causing hypoxaemia and cyanosis. The severity depends on the precise anatomical arrangement,2, 4, 6–8 being maximal when the venous drainage from the upper body is exclusively via the left superior caval vein into the left atrium, representing approximately two-fifths of the total systemic venous return. On frontal chest roentgenography, the upper mediastinum may be widened by an opacity crossing the aortic arch, corresponding to the left superior caval vein, and associated, as in our patient, with mild cardiomegaly,3, 4 though the radiograph may be completely normal.2 On the surface electrocardiogram, left ventricular hypertrophy may be present.2, 4
The diagnosis is made by cardiac catheterization performed for diagnostic purpose in presence of a congenital heart defect, when placing a pacing electrode, or when inserting a perfusion catheter. The diagnosis can also be suspected by isotopic techniques, which show a right-to-left shunt. Contrast echocardiography is also diagnostic, with the contrast material appearing first in the left atrium following intravenous injection in the left arm.9 Complications can be produced by paradoxical embolization, or abscess of the brain causing epileptic seizures.2, 7, 8
In view of these potential complications, surgical treatment is indicated, even in asymptomatic patients.2, 4, 8 The left superior caval vein, as in our case, is tunnelled into the right atrium by placement of an intra-atrial patch.4, 7, 10 Clinical and echocardiographic follow-up is necessary, even in absence of symptoms, should there be, as in our patient, subsequent narrowing of the intra-atrial baffle. In presence of isolated and refractory hypoxemia in the absence of an overt cardiac defect, therefore, anomalous systemic venous return should always be suspected, which can be confirmed by contrast echocardiography.
Acknowledgement
We thank Rodolphe Ruffy for the English editing of the manuscript, and Mathilde Ferry for the three-dimensional reconstructions of the computed tomographic scan.
