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Total anomalous systemic venous drainage to the left atrium: An entity reviewed and investigated

68%). There was no evidence of congestive ABSTRACT We present three unusual cases of total anomalous systemic venous drainage (TASVD) where all the systemic veins were abnormally connected to the atrium that drained into the left ventricle (LV). All three patients had features consistent with left atrial isomerism. Based on the available evidence and review of literature we propose that TASVD be included as a part of the syndrome of left atrial isomerism. A classification for TASVD is also proposed with surgical implications.


INTRODUCTION
Total anomalous systemic venous drainage (TASVD) is an exceptional form of congenital heart disease, wherein all systemic venous flow, including the right superior vena cava (RSVC), persistent left SVC (LSVC), inferior vena cava (IVC) (which may be interrupted), and coronary sinus, drain into the atrium draining into the morphologic left ventricle (LV). We describe three patients of this rare entity. Available literature is reviewed and a classification proposed.

Case 1
A 5-year-old girl was admitted to our hospital for evaluation of mild cyanosis with a room air oxygen saturation of 86%. There was no evidence of congestive heart failure. Her height and weight both ranked in the 90 th percentile. Echocardiography revealed left atrial isomerism [ Figure 1]. There was ventriculo-arterial concordance. Left atrium and LV were dilated (LV end diastolic Z score +2.8) [ Figure 2]. The branch pulmonary arteries were normal in size. All the pulmonary veins and systemic veins including the hepatic veins drained into the left-sided atrium and connected to the LV. A sizable fossa ovalis atrial septal defect was seen. The aortic arch was right sided (the features have been highlighted in [ Table 1]. Findings were confirmed by computerized tomography (CT) scan [ Figure 3]( Table 2,3). The child underwent biventricular repair via an atrial septation and a baffle, which routed venous drainage to appropriate ventricles. At surgery, both atrial appendages were left sided in morphology. At 1-year follow-up, the child was doing well with normal oxygen saturation and unobstructed systemic venous drainage.

Case 2
A 5-year-old child was observed to have cyanosis (oxygen saturation of 68%). There was no evidence of congestive Total anomalous systemic venous drainage to the left atrium: An entity reviewed and investigated drained to the left sided atrium. There was double outlet of the right ventricle (RV) with side-by-side great vessels. Nonrestrictive perimembranous ventricular septal defect was routable to aorta, with bidirectional shunting. Aortic arch was right sided. There was severe pulmonary stenosis with confluent and normal branch pulmonary artery sizes. CT scan confirmed the echocardiographic findings [ Figure 4a and b] [ Table 2,3]. The child underwent successful LV to aorta tunneling with an RV to pulmonary artery conduit along with atrial septation. Morphology of both the atrial appendages at surgery was left sided.

Case 3
A 2-year-old boy was incidentally found to be cyanotic with oxygen saturation of 75%. Echocardiographic examination showed left atrial isomerism with pulmonary veins draining to the left-sided atrium. Hepatic vein and bilateral SVC also drained to the left-sided atrium. The IVC ascended on the right of the spine, but crossed the midline and drained to the left sided atrium. There was a small fossa ovalis atrial septal defect with left to right shunt, ventriculo-arterial concordance, D-loop ventricles, and confluent and adequate sized branch pulmonary arteries. The RV was hypoplastic and bipartite. Ventricular function was normal (elaborated under Table 1). CT scan showed a midline liver with polysplenia, with associated agenesis of the tail of the pancreas ( Table 2). Rest of the cardiac findings was same as that described in echocardiographic evaluation [ Figure  5a and b]. The child underwent bidirectional Glenn shunt and atrial septectomy with banding of the main pulmonary artery. He has been doing well at 4 years follow-up and is now planned for Fontan conversion.

DISCUSSION
TASVD defies the guiding rule that the drainage of IVC serves as a reliable indicator for the chamber to be classified as right atrium. Although one exceptional case   was reported where all systemic venous blood returned to the coronary sinus, [1] the openings of total anomalous systemic veins are much more commonly connected to the left atrium. [2][3][4][5][6][7][8][9][10] All of our cases had features consistent with left isomerism. Literature review provides 14 cases of TASVD [ Table 4]. Five of the seven cases reported in the recent literature (after 1980, when the concept of isomerism was described) had features of left isomerism. Thus, it would be reasonable to suggest that the diagnosis of TASVD in any patient should be pointer to the presence of left isomerism. The lack of commitment regarding features of isomerism prior to 1980 is probably on account of the lack of awareness of the concept of isomerism prior to the period 12 (the same has been highlighted in Table 4).
Most of the cases were elegantly compiled by Zhang et al., and the present review owes much to their contribution. [13] We

Drainage of IVC type Isomerism Classification
Gueron et al. [6] 1 1969 LA LA I Miller et al. [7] 1 1965 LA LA Not committed I Viart et al. [8] 1 1977 No LA LA Non committed I Krayenbuhl et al. [2] 1 1977 LA Interrupted NA I Danielson et al. [3] 1 1973 LA Interrupted Yes (left) II Pearl et al. [14] 1 1980 NA NA NA NA I Johnson et al. [4] 1 2002 LA Interrupted Not commented II Roberts et al. [5] 1 1972 LA LA Interrupted No details II Zhang et al. [13] 1 2009 LA LA LA No II Turkoz et al. [9] 1 2010 No LA Interrupted Left isomerism II Barrea et al. [10] 1 2010 Left hetrotaxy Ravindranath et al. [  Hemodynamically, the left atrium forms the mixing chamber in the circuit, and hence, similar to the case of a total anomalous pulmonary venous drainage, oxygen saturation is equal in all the chambers. Although echocardiography is able to delineate most of the observations, a CT scan helps confirm drainage of all veins concerned to facilitate surgical intervention.
Surgical intervention is guided by associated cardiac morphology. In the presence of isolated TASVD, atrial septation with appropriate routing of veins suffices.
In the presence of associated lesions a more complex intracardiac repair with rerouting of the veins may be done. In the presence of associated extreme ventricular imbalance, a univentricular pathway may need to be resorted to.
All three of our cases had bilateral left atrial appendages. Available literature does not always comment on atrial morphology. Hence in such cases, it was impossible to decide laterality, or the lack of it. However, most described cases of TASVD do gravitate into bilateral left sidedness. On the basis of this experience and review of literature, we suggest that that presence of TASVD indicates a strong likelihood of left isomerism.