Awareness of systemic venous abnormalities, especially left superior vena cava, is critical when considering a left SVC approach to the heart in patients undergoing defibrillator or pacemaker placement, and when using retrograde cardioplegia for surgical procedures requiring cardiopulmonary bypass .
In our study, our patients were presented with either manifestations of systemic venous obstruction or manifestations of associated congenital cardiac anomalies, our results agree with Berko et al. , who reported no significant difference in symptoms in patients with systemic vascular variants and anomalies.
IVC abnormalities represented 7% of the studied group, 3.7% of which were congenitally interrupted IVC with either azygos (2.6%) or hemiazygos (1.1%) continuation. Two-thirds of those patients had left isomerism, while the rest had an isolated IVC interruption. This finding is consistent with Obernosterer et al. , who reported that the IVC anomalies have a prevalence of 0.07–8.7% in general population.
We relatively agree with Mandato et al. , who stated that the interruption of the inferior vena cava (IVC) with azygos continuation is a rare congenital anomaly. In contrast, Aborashed et al. , reported that the azygos/hemiazygos continuation percentage reaches 23.5% of the studied population. This difference may be because they had a larger sample size.
In agreement with Hollingsworth et al. , who reported that IVC thrombosis is considered rare, IVC thrombosis in the current study represented only 3.3% of the studied group and was common among drug addicts.
The diagnosis of PLSVC is crucial prior to some cardiac surgeries, such as venous rerouting procedures, cavo-pulmonary anastomosis, and heart transplantation .
In our study, superior vena cava abnormalities accounted for 36.58% of the detected abnormalities among 5.6% of the studied population. The prevalence of persistent left SVC (PLSVC) was 2.2%, while the prevalence of acquired lesions was 3.3% in the form of SVC syndrome or SVC aneurysm; 2.96% and 0.37%, respectively.
Our results agreed with Aborashed et al. , who found that persistent left SVC is considered the most frequent anomaly of thoracic venous anomalies along with partial anomalous pulmonary venous return.
In our study the prevalence of SVC syndrome, including both SVC indentation and thrombosis, was nearly 3%. It accounted for 19.5% of the detected abnormalities. This finding was attributed to mediastinal malignancy (37.5%) or the presence of central vein catheters (62.5%). In contrast, Birch et al. , stated that SVC syndrome resulting from SVC and internal jugular vein (IJV) thrombosis is rare. Rice et al. , in their study reported that, malignancy is the most common cause of the superior vena cava syndrome (60%); however, they reported an increasing incidence of benign etiologies of SVC syndrome due to the increasing use of intravascular devices .
Superior vena cava aneurysm is a very rare mediastinal vascular lesion accounting for 0.37% of the studied population. To our knowledge, the first case was reported by Abbot  in 1950, and approximately 37 cases were only reported till 2017. These results agree with Janczac et al. , and Sharma et al. .
Anomalous left brachiocephalic vein (ALBCV) is a rare systemic venous anomaly (1%). This vein takes an abnormal retro-aortic course beneath the aortic arch to create the superior vena cava. This condition is frequently seen in association with other congenital anomalies, mostly tetralogy of fallot (TOF) and right sided aortic arch [10, 16]. ALBCV accounted for 1.1% (3/270) of our studied population and 7.3% of the detected anomalies where two cases were associated with TOF and one with right isomerism.
The levoatriocardinal vein (LACV) is an extremely rare form of pulmonary systemic connection. Approximately 50 cases were reported in the literature till 2015. It originates from the left atrium (68%) or pulmonary vein (32%) and drains into one of the systemic venous structures, mostly into the left brachiocephalic vein (LBCV) (48%) [10, 17]. In our study, LACV accounted for 2.4% of the detected anomalies with a prevalence of 0.37%. While the whole left lung is drained by a conjoined left pulmonary vein, two small pulmonary veins drain left upper lung lobe into LACV. It was associated with patent ductus arteriosus (PDA) and atrial septal defect (ASD).
In our study, there is a highly significant excellent agreement between both observers regarding the role of multidetector computed tomographic angiography (MDCTA) in delineating thoracic venous abnormalities. We recommend using MDCTA as a first line diagnostic tool that can accurately delineate systemic venous abnormalities before interventional procedures.
Limitations to this study were: First, the lack of reference standard which was overcome using inter-observer agreement method. Second, respiratory motion and high heart rate in children that we partially overcame by using intravenous Fentanyl by anesthesiologists. Third, we included a wide range of ages in the study. Finally, and most important, it is a retrospective analysis involving a selected group of patients, this makes the proportion of normal subjects to those with congenital heart disease (CHD) very different from the true proportion in the population (selection bias).