Left Superior Vena Cava Draining Into Left Atrium in Tetralogy of Fallot—Four Cases of a Rare Association

Case 1

Case 1 was a 4-year-old male child with diagnosis of TOF, short segment pulmonary atresia, and a type I aortopulmonary window (APW) which in itself is a very rare association. In addition to echocardiography, computed tomographic (CT) pulmonary angiography revealed stenosis of the right upper pulmonary vein at its insertion into LA and presence of bilateral superior vena cavae (SVCs) with LSVC draining into LA (Figure 1). An innominate vein was present.

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Figure 1.

Computed tomographic pulmonary angiography showing LSVC draining into LA. LA indicates left atrium; LSVC, left superior vena cava.

Surgical correction was performed under standard cardiopulmonary bypass and cardioplegic arrest of the heart. The APW was closed with polytetrafluoroethylene patch using anterior sandwich patch technique. The ventricular septal defect (VSD) was closed with a synthetic patch. The right ventricular outflow was reconstructed with a transannular patch of autologous untreated pericardium incorporating a monocusp made of glutaraldehyde-treated autologous pericardium. The right upper pulmonary vein of adequate size was found. A search was made for an LSVC but no intrapericardial venous channel was found entering into heart. As the innominate vein appeared sizeable, it was assumed that an error had been made in the CT interpretation.

However, persistent systemic desaturation in the immediate postoperative period despite clear lung fields prompted a bedside contrast echocardiography which revealed dense filling of the LA with contrast (agitated saline) injected into the left arm (Figure 2A and B). The patient was reexplored and an LSVC (around 4 mm) was found draining into LA. It was placed quite posteriorly and hidden behind the pericardial fold of ligament of Marshall. As there was an innominate vein, we ligated the LSVC with immediate improvement in arterial oxygen saturation. The subsequent postoperative course was uneventful.

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Figure 2.

Echocardiography before (2A) and after (2B) injection of agitated saline (contrast) in left arm. Contrast filled up (arrow) the LA instantaneously. LA indicates left atrium.

Case 2

Case 2 was a 10-year-old male diagnosed with TOF. The echocardiography did not reveal any systemic venous abnormalities. We performed CT pulmonary angiography as a part of our unit protocol for preoperative evaluation of adult patients with TOF, for the purpose of delineating pulmonary artery anatomy and excluding aortopulmonary collaterals. The CT showed an LSVC draining into LA with no innominate vein.

The patient underwent total correction including patch closure of VSD, infundibular resection, pulmonary valvotomy, and right ventricular outflow reconstruction with transannular patch of autologous pericardium. The LSVC was smaller than right SVC. There was also a small innominate vein, hence the LSVC was ligated. This patient made an uneventful recovery with no evidence of left facial or left upper limb venous congestion.

Case 3

Case 3 was a 1-year-old male child admitted with diagnosis of TOF. Echocardiography revealed presence of bilateral SVCs with no bridging vein. The LSVC was draining into coronary sinus (CS). No preoperative contrast echocardiography was performed. The child underwent VSD closure, infundibular resection, and right ventricular outflow tract augmentation with short transannular patch. Coronary sinus was found to be dilated enough not to suspect any other aberrant drainage of LSVC. The LSVC was not cannulated but was loosely snugged during the procedure.

The child experienced severe desaturation (SpO₂ 80%) in the intensive care unit. A left external jugular venous line was secured to perform bedside contrast echocardiography. The contrast immediately filled LA. The patient was taken back to the operating room. The LSVC was ligated. We monitored both right SVC and left external jugular venous pressure. There was no significant pressure difference. Oxygen saturation improved instantaneously.

However, the child continued to have some desaturation (SpO₂ 90%) even after reexploration. Contrast echocardiography was repeated, which showed contrast reaching into right atrium and then shunting right to left into LA at the level of the opening of the CS, suggesting the presence of an unroofed CS defect (rather than LSVC to CS as was surmised in the operating room). After extubation, the saturation improved and the baby was discharged home with 100% saturation.

Case 4

Case 4 was a 29-year-old female who was admitted with tetralogy-type physiology. She was in NYHA II and her room air saturation was 90%. Echocardiography showed dextrocardia with both right SVC and inferior vena cava draining into right-sided right atrium. The LSVC was opening into LA without any bridging vein. There was large subaortic VSD with significant overriding of aorta. Right ventricular outflow tract was severely obstructed at infundibular and valvular level.

Cardiac catheterization showed both great vessels arising from right ventricle. The LSVC was confirmed to be opening into LA. Patient was subjected to cardiac magnetic resonance imaging to determine the routability of VSD. Magnetic resonance imaging also confirmed the presence of bilateral large superior vena cavae and LSVC was connecting directly to LA (Figure 3).

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Figure 3.

Cardiac MR BTFE sequences (gradient echo sequences)—white blood imaging showing LSVC opening into LA. BTFE indicates balanced turbo field echo; LA, left atrium; LSVC, left superior vena cava; MR, magnetic resonance.

Intraoperatively, apart from large bilateral SVCs, we found a right ventricular diverticulum arising near the apex of heart with surrounding adhesions. After initial dissection, the patient was put on cardiopulmonary bypass (both SVCs were cannulated). The blind diverticulum traversed across the diaphragm for short distance. After excising the diverticulum, right ventricle was repaired with continuous 4-0 Prolene. The heart was arrested with cold blood cardioplegia. The VSD was carefully inspected through tricuspid valve for its routability. A right ventriculotomy was made and intracardiac routing was done by a large Dacron patch. Right ventricular outflow was repaired by infundibular resection and pulmonary valvotomy without any transannular patch. We tried to route LSVC intra-atrially into the right atrium. But it seemed difficult, considering the abnormal position of the heart. Therefore, LSVC was implanted into main pulmonary artery (left hemiGlenn). This patient received postoperative anticoagulation.

Clinical Implications

An LSVC draining into CS is of little hemodynamic consequence. The condition is mostly asymptomatic and detected incidentally during an invasive procedure. Mert et al² reported a case of VSD closure with postoperative desaturation. Chest X-ray demonstrated tip of the central venous catheter inserted through left internal jugular vein taking an unusual course towards LA.

A persistent LSVC can cause severe complications like fatal arrhythmias and CS thrombosis during central catheterization and permanent pacemaker/cardioverter implantation. ⁴ Retrograde cardioplegia becomes ineffective during open-heart surgery if LSVC is not snugged. ⁵

About 40% of patients with persistent LSVC have various accompanying congenital heart defects including atrial septal defect and VSD, bicuspid aortic valve, cor triatriatum, coarctation of aorta, and CS ostial atresia. ⁶ Isolated LSVC without its right-sided counterpart or LSVC draining into LA is uncommon. In approximately 8% of cases, the LSVC drains into LA. ⁷ These two systemic venous anomalies are almost invariably associated with congenital heart defects and, therefore, warrant detailed echocardiographic examination. Sarodia and Stoller have reported a 20% incidence of persistent LSVC with TOF. ⁸ Existing literatures reveal very few single-case reports of LSVC to LA in tetralogy physiology. The first case was reported by Shumacker and associates ⁹ who described anastomosis of LSVC to right atrium after detaching it from LA. But the cava-to-atrium anastomosis was occluded by right ventricular aneurysm at the site of transannular patch. Inaoka et al reported a similar association in the presence of atriovisceral heterotaxy syndrome. ¹⁰ The last reported case of LSVC draining into LA in the presence of TOF was in 1987 by Mohan and colleagues. ¹¹

An LSVC draining into LA produces significant right to left shunt with unexplained systemic desaturation. It is also implicated in cases of paradoxical thromboembolism with its attendant neurological complications like stroke and brain abscess. ¹²

Presence of LSVC increases the incidence of cardiac arrhythmias, especially atrial fibrillation. Anatomical and architectural abnormalities of sinus node and conduction system have been reported in the past. ¹³ Recent studies have highlighted the arrhythmogenic potential of ligament of Marshall. This ligament contains the vein of Marshall whose muscular sleeve continues into the CS. ¹⁴

Diagnosis

As mentioned earlier, LSVC is almost always found incidentally during echocardiographic examination. Transthoracic echocardiography demonstrates dilated CS if LSVC is draining into it. Any suspicion of LSVC should be followed by “saline contrast” echocardiography or “bubble study.” The following diagnostic criteria are used to locate the drainage of LSVC ⁴ :

the presence of dilated CS in absence of evidence of elevated right atrial pressure,

Computed tomography and cardiac magnetic resonance (CMR) venography have improved the diagnosis of systemic venous drainage abnormalities. An LSVC is very commonly confused with partial anomalous pulmonary venous drainage of left upper lobe vein. Transthoracic echocardiography sometimes fails to differentiate between the two due to poor acoustic windows. Both CT and CMR can afford multiple plane analysis. But CT is limited by the need of iodinated contrast and increased radiation exposure, which make CMR preferable, particularly in young patients. In the postoperative period, an LSVC to LA should be suspected in any patient with diagnosed LSVC and persistent desaturation in the absence of lung pathology and residual intracardiac shunt.

Unroofed CS with LSVC draining into LA (as in case 3) should be distinguished from persistence of embryonic connection of a systemic vein (like LSVC) to LA. An LSVC is associated with unroofed CS in 75% of cases. Unroofed CS represents a very rare cardiac anomaly in which the common wall between the CS and LA is partly or completely deficient. Unroofed CS and LSVC are further associated with various complex congenital heart diseases like heterotaxy syndrome. ¹⁵ Unroofed CS is very difficult to diagnose preoperatively. It should be suspected in patients with left-to-right interatrial shunt and unexplained systemic desaturation. Transthoracic echocardiography is not very sensitive in delineating these posterior structures. Cardiac magnetic resonance and gated cardiac CT are emerging as very useful noninvasive tool for evaluation of coronary venous system and posterior cardiac structures. ¹⁶ Final diagnosis is confirmed on the basis of intraoperative findings.

Available Surgical Options

The surgical approach to LSVC draining into LA has to be individualized. Ligation of LSVC is a simple choice if the proximal venous pressure does not rise above 30 mm Hg. ¹⁷

In our first patient, LSVC was smaller than right SVC and there was an innominate vein. In the second patient, though innominate vein was very small, ligation of LSVC did not result in elevated central venous pressure. Our third patient probably had LSVC draining into CS but with concomitant unroofed CS defect. Ligation of LSVC prevented bulk of right to left shunt and improved saturation partially. But the right to left shunt continued at atrial level due to unroofed CS defect which diminished significantly after the effect of positive pressure ventilation was withdrawn. A similar case was described by Jian et al. ¹⁵ The fourth patient recovered very smoothly. All these patients were discharged with 100% saturation in room air.

There are many surgical options described in literature. These include intra-atrial baffle rerouting, ¹⁷ reimplantation into right atrium or left pulmonary artery, ¹⁸ and graft interposition into right atrium. ¹⁷ All these procedures have their own shortcomings. Intra-atrial baffle rerouting seems to work well but the long-term patency is questionable. ¹⁹ Reimplantation into right atrium necessitates extensive mobilization of LSVC leading to undesirable stretching. The vein or any interposition graft may also get compressed between the sternum and aorta as in the case described by Shumacker and collegues. ⁹

Komai et al ¹⁹ described an ingenious technique with an inverted flap of LA appendage to construct an intra-atrial conduit in a 4-year-old girl with persistent LSVC with atrial septal defect. The remaining defect in atrial septum was closed with pericardium. Though the short-term result was satisfactory, long-term patency of this procedure is not known.

To summarize, we feel that in the presence of a bridging vein, LSVC opening into LA can be safely ligated (cases 1 and 2). When there is no bridging vein, venous pressure should be measured during test occlusion of the vessel. If the proximal venous pressure does not exceed 30 mm Hg, ¹⁷ it is safe to ligate LSVC (case 3). There may be some facial puffiness which gradually subsides on its own by nursing with head-up position. In the instance of test-induced upper systemic venous hypertension or in the presence of a large LSVC without any bridging vein (case 4), it must be rerouted into right atrium or reimplanted into right atrium (with an interposition graft) or left pulmonary artery.