The authors describe a patient whose persistent left superior vena cava was first suspected because of difficulty in placing a right internal jugular venous catheter.
A 32-year-old woman at 28 weeks' gestation presented to the emergency department with a complaint of a severe headache of relatively sudden onset. She stated that she had not received any prenatal care and had been using methamphetamines, marijuana, and alcohol the week before presentation. She denied any past medical history and any complications with her previous pregnancies.
The patient was noted to have a blood pressure of 224/108 mm Hg, elevated liver function values, and a decreased platelet count, consistent with a diagnosis of HELLP (hemolysis, elevated liver enzymes, low platelets) syndrome. Her blood pressure was controlled with labetalol, and she was prepared for emergent cesarean delivery. Before surgery, the anesthesiologist attempted to place a right internal jugular central venous catheter but was unable to thread the catheter.
After surgery, the patient was transferred to the ICU. A left internal jugular central venous cathe- ter was placed without complications. A chest radiograph was obtained to confirm the position of the catheter (Figure 1). A CT scan with contrast confirmed the diagnosis that was suspected on the basis of the radiograph (Figure 2).
Persistent left superior vena cava (SVC) is an uncommon congenital defect. It is the most common anomaly of thoracic venous return.1 It is usually asymptomatic and is most often diagnosed on placement of a central venous catheter or pacemaker through the left internal jugular or subclavian vein.
In embryologic development, the venous system is symmetric, with bilateral anterior cardinal veins draining the cranial portion of the embryo. In the eighth week of gestation, the left brachiocephalic vein develops and anastomoses with the right anterior cardinal vein, which becomes the right SVC; this is followed by the regression of the left SVC.2 Lack of regression of the left SVC leads to a persistent left SVC.
In an unselected postmortem series, the prevalence of persistent left SVC was 0.3%.3 In another study, a persistent left SVC was detected in 5 of 4000 radiographs obtained after central venous catheter placement.4 In the vast majority (approximately 82%) of cases, there is persistence of the right SVC, along with an anomalous left SVC.5
The persistent left SVC usually drains into the right atrium via the coronary sinus, which results in normal physiology and no evidence of hemodynamic compromise. In rare instances, it can drain into the left atrium, causing right-to-left shunting with variable degrees of cyanosis.6
Persistent left SVC is important for its association with other congenital cardiac anomalies. In various studies, persistent left SVC was found to occur in 4.1% to 11% of patients who underwent angiocardiography for confirmed or suspected congenital cardiac anomalies, with the highest incidence in patients with cardiac septal defects.3,7,8 In one study, persistent left SVC was found in 20% of cases of tetralogy of Fallot and in 8% of patients with Eisenmenger syndrome.9
The diagnosis is typically suggested by a chest radiograph after insertion of a central venous catheter, as in our patient. It can also be suggested on plain chest radiographs; a shadow of the persistent left SVC can cause widening of the aortic shadow with a mediastinal bulge under the aortic arch.1
Several techniques can be used to confirm the diagnosis. CT with contrast reveals the persistent left SVC draining into the coronary sinus. The diagnosis can be made noninvasively by transthoracic echocardiography in conjunction with Doppler or contrast ultraso- nography. An unusually large coronary sinus appears as a dilated echo-free space posteriorly in the atrioventricular groove between the left atrium and ventricle, which can be enhanced with saline contrast.10
Transesophageal echocardiography is more sensitive for the diagnosis of persistent left SVC and associated cardiac anomalies, such as atrial septal defects, as well as of anomalous connections of pulmonary veins.11 MRI, although less frequently used, can give more accurate images of the heart and large vessels.
There are several important clinical implications of this anomaly. First, placement of a central venous catheter into a persistent left SVC can be mistaken for placement into other structures that occupy similar positions, such as the subclavian or carotid artery, the mediastinum, or pleural space.12 Second, cardiac arrhythmias, such as ventricular fibrillation, have been noted in patients with persistent left SVC, possibly as a result of dilation of the coronary sinus, which leads to stretching of the atrioventricular node and His bundle.13
Third, as noted above, there is an increased risk of other cardiac anomalies, such as atrial septal defects, with increased risk of paradoxical emboli; the discovery of a persistent left SVC may be the first clue to paradoxical emboli. Finally, a persistent left SVC may cause difficulty in placing a pulmonary artery catheter because of the narrow angle of the coronary sinus.
This anomaly is almost always an incidental finding and does not require specific treatment. Our patient recovered uneventfully, was discharged after 3 days, and had no subsequent complications.
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