Isolated left-sided superior vena cava

Clinical History

3-year-old female patient was admitted with leukaemia and a right-sided central venous catheter (CVC) was inserted to administer chemotherapy. A control chest X-ray was performed to check the placement of CVC which couldn't be explained - an anatomical variant was suspected and CT was performed to confirm diagnosis.

Imaging Findings

Chest X-ray:

A right-sided Central Venous Catheter (CVC) can be seen with the tip at the upper border of the left main bronchus /aorto-pulmonary window. This placement could only be explained by an anatomical variant like left-sided Superior Vena Cava (SVC). A CT was performed to confirm the anatomical variant.

CT chest and abdomen:

CT confirms the presence of suspected anatomical variant. An isolated left sided SVC draining into right atrium via the coronary sinus was seen. CVC was placed in the left-sided SVC.

Discussion

Background:

Persistent left superior vena cava (PLSVC) is a rare but important congenital thoracic venous anomaly, results from the persistent left anterior cardinal vein with a prevalence of 0.3-0.5 % in the general population and about 12% in patients with congenital heart diseases. [4, 5] In 82-90% of PLSVC cases, right SVC is also present, results in duplication of SVC, but in only 10–20% cases of PLSVC, there will be isolated PLSVC, which usually drains into the right atrium via the coronary sinus without haemodynamic consequences, is therefore asymptomatic and an incidental finding on imaging studies done for unrelated purposes. [2, 1] Very rarely, LSVC may drain in the left atrium resulting in a right to left shunt. [5] Isolated PLSVC is at high risk for associated anomalies including atrial septal defect, ventricular septal defect, tetralogy of Fallot, bicuspid aortic valve, aortic coarctation, mitral atresia, and cor triatriatum [3, 5]

Clinical Perspective and outcome:

Often the frontal chest radiographs, done to evaluate positioning of central venous catheters showing unusual left-sided downward course are a first clue to PLSVC, which can be misdiagnosed as arterial, mediastinal, or pleural placement. [3, 5] PLSVC may also cause difficulty in placement of pacemakers, implantable cardioverter-defibrillator leads, and Swan-Ganz catheters because of the narrow opening from the coronary sinus to the right atrium. [3, 4] PLSVC is a relative contraindication for retrograde cardioplegia during coronary artery bypass grafting, which may be ineffective because of inadequate myocardial perfusion. [3] Lack of knowledge about anomaly can lead to complications such as arrhythmia, cardiogenic shock, cardiac tamponade, and coronary sinus thrombosis if pacemaker leads or catheters have been inserted via PLSVC. Therefore it is important that cardiothoracic surgeons, anaesthesiologists, intensivists and radiologists are aware of the anomaly before planning surgical and radiological vascular procedures. [5]

Imaging perspective:

Radiologically, LSVC should be suspected if there is a widened aortic shadow, paramediastinal bulge or a low density line along the upper left margin of the heart on a posteroanterior view which can be misdiagnosed as pathologic mass. [4] CT or cardiac MR provides direct visualization of an abnormal course of veins. [4] Agitated saline injection via the left antecubital vein (Bubble study) and performing trans-thoracic echo is a safe, harmless and inexpensive test that can help detect LSVC when suspected. [4]

Teaching points:

Being a rare anomaly, it takes a high index of suspicion but should be considered on detecting dilated coronary sinus on echocardiography or left paramediastinal bulge on chest radiographs.

Differential Diagnosis List

Final Diagnosis

Isolated left-sided superior vena cava.

URL:	https://www.eurorad.org/case/13686
DOI:	10.1594/EURORAD/CASE.13686
ISSN:	1563-4086