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2006-10-24-10 Persistent left superior vena cava © Manson www.thefetus.net/


Persistent left superior vena cava

Francois Manson, MD1, Kathleen Comalli Dillon, BA, RDMS2

1 Fecamp, France

2 Kaiser Permanente, Vallejo, California, USA

 

We present the case of a 36-year-old primigravida with normal first trimester sonogram (CRL:  65 mm; NT: 1.6 mm).  Her triple-marker screen was also normal (1/5000). The following images were obtained at 23rd week of gestation.  They outline the anomalies we found:  persistent left SVC, cardiac malposition, and a poorly coiled cord.

1) Persistent left superior vena cava

Image 1:  “Three-vessel  view”
We observed the presence, to the left of the pulmonary artery trunk (PA), of a fourth (unexpected) vascular structure corresponding to a persistent left superior vena cava (LSVC).

Image 2: Axial image near the four-chamber view.
We noted the presence of the descending part of the dilated coronary sinus (CS) as a thin echogenic circle between the left atrium (LA) and the left ventricle (LV).

 

Image 3: Axial view situated a bit caudally to image 2.
In the left atrium we can see the horizontal part of the dilated coronary sinus as a thin transverse echogenic line (left image: atrioventricular valves (AV) closed, and right image: AV valves open).

 

2) Cardiac malposition  

Image 1:
In this strict axial section, the apex of the heart is displaced toward the right.  This results from a deviation of the cardiac axis. This anomaly may be isolated, but may equally be associated with other cardiac anomalies (mirror-image heart, asplenia/polysplenia, inversion of the ventricles, atrioventricular septal defects, double-outlet right ventricles, or single atria ). In the present case, the only associated anomaly was the persistent left superior vena cava.

 

Image 2:
The right-axial deviation of the heart.

3) Poorly coiled cord:

Image 1: Longitudinal section of the cord.
This anomaly appears relatively often, being associated most frequently with IUGR and fetal distress.  This is most likely due to the lesser vascular resistance of the cord to compression.

Pathophysiology:

Persistent left superior vena cava is also called double superior vena cava. The essential criterion leading to persistent left superior vena cava is the failure of regression of the left anterior cardinal vein and of the left horn of the venous sinus between the 24th and 56th days of pregnancy. Normally, during this time of development, we can see (Diagram 1):


• Regression of the caudal portion of the left anterior cardinal vein, ACV (which drains the blood from its left superior branch) and from the left part of the cephalic pole via the intermediaries, respectively, of the left subclavicular vein, SCV, and the left jugular vein, JuV ; 
• Appearance of an anastomosis between the right and left thymic and thyroid veins.  This anastomosis gives rise to the left brachiocephalic vein, which, after merging with the right brachiocephalic vein, gives rise to the right superior vena cava ;
• Leftward extension  of the left horn of the venous sinus, which loses its connection with the left anterior cardinal vein and becomes the coronary sinus.  The coronary sinus will finally drain only myocardial venous blood.

As a result of these modifications, all venous blood from the superior branches and from the cephalic pole is drained by the superior vena cava (situated on the right), which flows from the right auricle.


Diagram 1:


AVC = anterior cardinal vein, PCV = posterior cardinal vein, UV = umbilical vein, VV = vitelline vein, Thym and Thyr V = thymic and thyroidal veins, R and L VSH = right and left venous sinus horns, LBCV = left brachiocephalic vein, RBCV = right brachiocephalic vein, JuV = jugular vein, SCV = subclavian vein, SVC = superior vena cava, IVC = inferior vena cava

In the case of persistent left vena cava (Diagram 2), the regression of the anterior cardinal vein and the anastomosis between the thymic and thyroid veins has not occurred. Due to this, the left jugular vein and left subclavicular vein drain into the anterior cardinal vein, which then takes the name of the left superior vena cava. In the great majority of cases of persistent left superior vena cava, the vena cava drains into the right auricle by the intermediary of a dilated coronary sinus. Much more rarely, the left superior vena cava flows directly into the left auricle.

Diagram 2:


LSVC = left superior vena cava, RSVC = right superior vena cava, DCS = dilated coronary sinus

 

 

 

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