Persistent Left Superior Vena Cava: An Intensivist's Experience and Review of the Literature

Rajit Pahwa, MD, Anand Kumar, MD

Disclosures

South Med J. 2003;96(5) 

In This Article

Discussion

The embryologic development of systemic and pulmonary veins is complex and subject to considerable variation. During normal development, the anterior cardinal veins, which drain the head, neck, and arm, unite with the posterior cardinal vein in the very early embryonic stage and enter the heart as the right and left horns of the sinus venosus. With the exception that the cardinal veins on the right and the left side drain into the right atrium, the cardinal venous system is bilaterally symmetrical at this stage. Most of the left-sided cardinal system disappears, leaving only the coronary sinus and a remnant known as the ligament of Marshall. Simple failure of obliteration of the left anterior cardinal vein results in the persistence of the LSVC. This usually drains into the right atrium via the coronary sinus. On rare occasions, when developmental arrest occurs at an earlier stage, the coronary sinus is absent and the persistent LSVC drains directly into the atrium.[2]

Individuals with LSVC usually possess a normal right superior vena cava, and thus the condition is not routinely detected. The physiology is normal, and there is no hemodynamic compromise. In rare instances, the LSVC drains directly into the left atrium and may cause a small right-to-left shunt. This lesion usually has little hemodynamic effect, although a variable degree of systemic cyanosis may be seen.[2]

The importance of a persistent LSVC lies in a greater prevalence of other associated congenital cardiovascular defects and significant incidence of rhythm disturbances.[3] Wood[4] found persistent LSVC in 20% of cases of tetralogy of Fallot and 8% of patients with Eisenmenger's syndrome. Hancock[5] reported a high prevalence of leftward P axis with a normal PR interval, but its significance is not clear.[6]

A previous case report suggested that a long catheter-insertion length to obtain a wedge tracing, lack of usual central venous pressure waves, and unexpectedly high cardiac output determinations should all suggest placement via LSVC.[7] Suspicion of LSVC may arise on the posteroanterior chest x-ray, where it may appear as widening of the aortic shadow, paramediastinal bulging, paramedian stripe, or a low-density line along the upper left margin of the heart.[8] The typical route of a PA catheter through the aberrant vessel is shown in Figure 1. On the posteroanterior view, the catheter is seen to pass inferiorly along the left border of the mediastinum within the LSVC. It crosses the midline obliquely via the coronary sinus and enters the right atrium. Computerized tomography of the chest shows a vascular structure along the left side of the arch of the aorta draining into the right atrium.

Persistent LSVC can be accurately diagnosed noninvasively by echocardiography in conjunction with Doppler and/or contrast ultrasonography. One of the clues to the diagnosis is an unusually large coronary sinus on two-dimensional views. It appears as a dilated, echo-free space posteriorly in the atrioventricular groove between the left atrium and ventricle. Saline microbubble contrast can be used to enhance the accuracy.

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