The Anomalies of Systemic Venous Connections in Children with Congenital Heart Disease

Anomalous systemic venous return (AVSR) may sometimes present as pathologic entities itself, or associated with other congenital heart defects. The presence of AVSR may require significant changes in surgical technique during the repair of congenital heart defects. The aim of our study was to assess the prevalence of anomalous systemic venous return and to determine the congenital heart anomalies accompanying AVSR in children. This study is based on a retrospective review of the medical records of 175 children who consecutively underwent cardiac catheterisation because that congenital heart disease. The most extensively diagnosed cardiac malformation was VSD (26.8%). ASVR was prevalent in 4.5% of patients. The most commonly diagnosed ASVR was persistent left superior vena cava (3.4%) and a second ASVR type was associated interruption of the inferior vena cava (IVC) with azygos vein continuation (1.1%). A systematic study of systemic venous connections should be performed in all those undergoing cardiac catheterisation as a prelude to open heart repair because it may require significant changes in surgical technique during the repair.


INTRODUCTION
Anomalous systemic venous return (ASVR) is an exceptional form of congenital heart disease in which all of the systemic veins, including the hepatic veins and the coronary sinus, drain abnormally into the heart (1).It is usually anatomically benign, and commonly does not imply haemodynamic consequences.However, ASVR is sometimes associated with atrioventricular canal, common atrium, atrial septal defect (ASD), ventricular septal defect (VSD) and heterotaxia, and it may necessitate important modifications in the surgical technique used during the repair of associated congenital heart defects.Therefore, precise definition of systemic venous connections is important in congenital heart disease to enable proper surgical correction (2).In this study, we present venous anomalies in children with congenital heart disease after catheter angiography over a 3-year period.

MATERIALS AND METHODS
Our study is based on a retrospective review of the medical records of 175 children who consecutively underwent cardiac catheterisation, due to congenital heart disease, at the department of paediatric cardiology in Selcuk University Medical Faculty Hospital, from 2010 to 2013.Transthoracic echocardiography, if necessary, electrocardiography and chest X-ray were performed for all of these patients, prior to cardiac catheterisation and angiography.All echocardiographic examinations were conducted using a commercially available echocardiographic machine (Toshiba, Aplio 50, Japan) equipped with 3.5 and 6.5 MHz transducers.Recordings were performed with patients in the supine or left lateral positions.The innominate vein was evaluated on the frontal plane and, if present, a left superior vena cava was visualised from the same position.The rightsided superior vena cava was visualised by employing a suprasternal notch approach.An enlarged coronary sinus could be demonstrated from a parasternal long axis view.Cardiac catheterisation was performed percutaneously at the right femoral vein, following premedication and local anaesthesia.The innominate vein injection was conducted during cardiac catheterisation, according to the routine practice of the study centre.Data regarding the type of congenital heart disease and persistence of the caval system were listed for each patient following diagnostic procedures, and the Statistical Package for Social Sciences (SPSS for Windows Version 15.00, Chicago, IL, USA) programme was used to assess the results.Distribution of data was analysed using the Kolmogorov-Smirnov test, according to which suitable parametric and non-parametric tests were selected.The parametric data are given as arithmetic means±standard deviation, and non-parametric data are given as medians (minimum-maximum).The Pearson chi-square test was used to compare categorical variables and comparison between groups was determined by Student's t test or Mann-Whitney U test (parametric data and non-parametric data, respectively).In the statistical evaluations, a p value of p<0.05 was regarded as significant.
The study protocol was approved by the local ethical committee.Informed consent was obtained from the participants and/or their guardians.

RESULTS
The study group consisted of 175 patients who consecutively underwent cardiac catheterisation at our study centre.Approximately 50.8% (89 of 175) of these patients were male, while 49.2% (86 of 175) were female, and the age range was 1 month-17 years (6.1±4.2 years).In this series, 173 patients had levocardia and two patients had dextrocardia.The most extensively diagnosed cardiac malformation was VSD (n:47, 26.8%) and another common cardiac malformation observed was ASD (n:45, 25.7%).The other cardiac anomalies found were coarctation of the aorta (n:23, 13.1%), patent ductus  1) and a second ASVR was associated interruption of the inferior vena cava (IVC) with azygos vein continuation (n:2, 1.1%), as shown in Figure 2. The detected venous return and accompanying congenital heart anomalies are shown in Table 2.

DISCUSSION
Normal systemic venous return consists of the connection of the superior vena cava (SVC) and IVC, as well as the coronary sinus, to the right atrium on the right side of the interatrial septum.The development of this venous system begins from the symmetric and paired cardinal and subcardinal veins in the 5-week-old embryo (3).Countless abnormalities of this system are com-   Persistent left superior vena cava (PLSVC) is a common congenital malformation of the thoracic venous system, with a prevalence estimated at approximately 0.3% in individuals with a normal heart and 4.5% in individuals with congenital heart disease (5).It is generally asymptomatic and is detected when cardiovascular imaging is performed for unrelated reasons.The well-developed azygos or hemiazygos vein is present and connects with some portion of the infrarenal IVC.Azygos continuation of the IVC on the left or right may occur in either situs solitus or left isomerism,(6) but does not necessarily imply absence of the suprarenal inferior cava, which may coexist in patients with situs solitus, although rarely.The bridging innominate vein connects the bilateral SVC, and, when present, runs in the anterior mediastinum, immediately in front of the origin of the brachiocephalic branches of the aorta.Partial anomalous hepatic venous connection is such that some, but not all, of the hepatic veins connect directly to the heart in an abnormal fashion, instead of to the suprarenal inferior cava or to the inferior cavoatrial junction.Total anomalous hepatic venous connection is such that all the hepatic veins connect directly to the heart, via one or more hepatic veins.This may be to the left or the right sided atrium, or to both, and the hepatic veins connect separately to the heart if the suprarenal inferior cava is present.This venous connection was present in all patients with left isomerism (6).The majority of systemic venous anomalies are accounted for by a few specific abnormalities.In one study, the overall incidence of systemic venous return was 3.8%, and 48% of these anomalies were represented by bilateral SVC, while 28% were represented by interrupted IVC (1).In our catheter angiography series, the prevalence of ASVR was 4.5%, and PLSVC was the most common abnormality of systemic venous return.Huhta et al. (7)  Bilateral SVC was reported in 0.3% of the general population in an autopsy series, while SVC has been reported in 3-5% of patients with congenital heart disease (9).Its draining into the right atrium, via the coronary sinus, is one of the more common systemic venous anomalies, and is frequently incidentally.If an abnormality is isolated, this finding is usually not clinically significant; however, it is frequently associated with an atrial septal defect or other intracardiac malformations (10).Although a lot of single case reports exist, studies showing incidence of systemic venous return are rare in the literature.Left SVC was observed in 6/175 (3.4%) of our patients.Azygos and/or hemiazygos continuation of the IVC has been reported to occur in 0.6% patients with congenital heart disease.It is important to define because inadvertent ligation of the azygos vein during surgical procedures must be completely avoided in such situations, and ligation has been known to cause death (9).In our series, infrahepatic interruption of the IVC with azygos or hemiazygos continuation was observed in 2/175 (1.1%) patients with congenital heart disease.

Table 2. Anomalous systemic venous return in relation with congenital cardiac anomalies
In conclusion, ASVR is a complex and varied group of lesions that are not uncommon in patients undergoing congenital heart surgery.Furthermore, such anomalies often dictate significant modifications in the conduct and timing of cardiac surgical procedures.The angiographic definition of systemic venous connections may lead to a small increase in the amount of fluoroscopy time during the catheterisation procedure, and the information that is gained is very useful.We believe that, patient's clinical condition permitting, a systematic study of systemic venous connections should be performed in all those undergoing cardiac catheterisation as a prelude to open heart repair.

Figure 1 .
Figure 1.Injection in an innominate vein (arrow), connecting the left and right superior vena cava.Posterioranterior view of the injection showing the catheter in the innominate vein and contrast material in the left superior vena cava and draining into the right atrium.A; innominate vein, B; left superior vena cava, C; right atrium.

Figure 2 .
Figure 2. Posterior-anterior view shows interruption of the inferior vena cava and the azygous vein that drained into the right atrium in child with ventricular septal defect.The catheter in the azygous vein (arrow).A; azygous vein, B; right atrium C; right ventricle, D; main pulmonary arter.