Persistent Left Superior Vena Cava​ (PLSVC) ​

Persistent left superior vena cava (PLSVC) represents the most common form of anomalous systemic venous return resulting from in utero failure of the regression of the left anterior and common cardinal veins (1-3).

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Incidence is estimated to be 0.3-0.5% of the general population and 4-9% of patients with congenital heart disease (CHD) (1,4).

In the early embryonic period, the right and left anterior cardinal veins constitute the main venous drainage of the cephalic portion, but the development of the left innominate vein at the 7th week of gestation and the regression of the proximal part of the left cardinal vein cause a usual pattern of right superior vena cava drainage, whereas the left cardinal vein becomes the ligament of Marshall.
PLSVC results from the failure of the involution of the left anterior and common cardinal veins (1). 

The exact cause of PLSVC is unknown.

The PLSVC starts at the junction of the left jugular and subclavian veins, runs anterior to the aortic arch and left pulmonary artery and on the lateral border of the left atrium; it joins the coronary sinus in the posterior left atrioventricular groove and drains into the right atrium in 92% of cases or into the left atrium in the remaining cases when the coronary sinus is partially or completely unroofed (2-3). Occasionally the right SVC is absent and the venous return from the upper body enters the coronary sinus to the right atrium. In the majority of cases, PLSVC has no clinical implications and no hemodynamic changes as venous blood continues to return to the right atrium (5-6).

PLSVC is associated with cardiac malformations in about 60% of cases, especially coarctation of the aorta, conotruncal anomalies and ventricular septal defects. This can be a part of Heterotaxy syndrome (with atrioventricular septal defect and/or anomalous pulmonary venous connection) (3-5). Associated extra-cardiac malformations (40% of cases) include spleen and bowel abnormalities in fetuses with heterotaxy syndrome and umbilical venous system anomalies (7).
Chromosomal anomalies, especially trisomy 21 and 18, are more likely to occur when PLSVC is associated with intra or extracardiac malformations. However, even when PLSVC is apparently isolated, the prevalence of aneuploidy is about 7-9% (4,6).

Recurrence risk is related to the recurrence of associated chromosomal anomalies.

On fetal ultraosund, the detection of PLSVC can be achieved or suspected in different planes of the fetal chest:
-    Four-chamber view: LSVC can be identified in cross section at the left border of the left atrium; a dilated coronary sinus (diameter: 3-7 mm) can be noted in the region of the mitral valve;
-    Three- Vessel and tracheal view: LSVC can be identified in cross section as a fourth vessel located to the left of the pulmonary artery;
-    Left parasagittal plane of the thorax and neck: it is possible to demonstrate the LSVC draining into the coronary sinus. 
Color Doppler may help to confirm the direction of the blood towards the heart in the parasagittal plane and to show blood flow towards the right atrium when applied to the dilated coronary sinus. Furthermore it can be useful to identify or confirm the absence of a left innominate vein between the left and right SVC (2-3).

Dilated coronary sinus with PLSVC can be misdiagnosed as an atrioventricular septal defect and atrial septal defect. 
Differential diagnosis between PLSVC and vertical vein in anomalous supra-cardiac pulmonary venous connection can be undertaken with colour Doppler, as the blood flow is toward the heart in LSVC (8).

PLSVC detected antenatally should  be followed by a detailed examination of the fetal anatomy, as it is frequently associated with heterotaxy syndromes, other cardiac/non-cardiac malformations and aneuploidies that can determine the outcome. Follow up scans should be arranged in view of the risk of coarctation of the aorta in the third trimester (1, 5).

ISUOG guidelines recommend that the three-vessel and tracheal view be included in routine pregnancy screening in order to improve the prenatal detection of PLSVC and its related findings (9).

Isolated PLSVC is a benign vascular anomaly and does not have any post natal hemodynamic consequences (4-7).
The fetal outcome depends on the associated cardiac and/or chromosomal anomaly.

Following the detection of PLSVC, a detailed fetal anatomy examination is recommended to rule out associated malformations, especially CDH. Follow up scans should be arranged to ascertain any additional anomalies, including coarctation of the aorta. 
The first-trimester combined risk for aneuploidies should be reviewed to evaluate the individual risk. Fetal karyotype and chromosomal microarray analysis (CMA) should be discussed with the parents. 
Neonatal echocardiography is also recommended (4,5).

1.    Galindo A, Gutiérrez-Larraya F, Escribano D, Arbues J, Velasco JM. Clinical significance of persistent left superior vena cava diagnosed in fetal life. Ultrasound Obstet Gynecol. 2007 Aug;30(2):152-61.

2.    Paladini D, Volpe P. Ultrasound of Congenital Fetal Anomalies. 2nd Edition. Taylor & Francis, 2014.

3.    Abuhamad A, Chaoui R. A Practical guide to fetal echocardiography: normal and abnormal hearts. Edition, 3. Lippincott Williams & Wilkins, 2015. 

4.    Gustapane S, Leombroni M, Khalil A, Giacci F, Marrone L, Bascietto F, Rizzo G, Acharya G, Liberati M, D'Antonio F. Systematic review and meta-analysis of persistent left superior vena cava on prenatal ultrasound: associated anomalies, diagnostic accuracy and postnatal outcome. Ultrasound Obstet Gynecol. 2016 Dec;48(6):701-708. doi: 10.1002/uog.15914. Epub 2016 Nov 1. Review.

5.    Choi EY, Hong SK, Jeong NY. Clinical characteristics of prenatally diagnosed persistent left superior vena cava in low-risk pregnancies. Prenat Diagn. 2016 May;36(5):444-8. doi: 10.1002/pd.4801. Epub 2016 Mar 27.

6.    Berg C, Knüppel M, Geipel A, Kohl T, Krapp M, Knöpfle G, Germer U, Hansmann M, Gembruch U. Prenatal diagnosis of persistent left superior vena cava and its associated congenital anomalies. Ultrasound Obstet Gynecol. 2006 Mar;27(3):274-80.

7.    Familiari A, Morlando M, Khalil A, Sonesson SE, Scala C, Rizzo G, Del Sordo G, Vassallo C, Elena Flacco M, Manzoli L, Lanzone A, Scambia G, Acharya G, D'Antonio F. Risk Factors for Coarctation of the Aorta on Prenatal Ultrasound: A Systematic Review and Meta-Analysis.Circulation. 2017 Feb 21;135(8):772-785. doi: 10.1161/CirculationAHA.116.024068. Epub 2016 Dec 29. Review.

8.    Volpe P, Campobasso G, De Robertis V, Di Paolo S, Caruso G, Stanziano A, Volpe N, Gentile M. Two- and four-dimensional echocardiography with B-flow imaging and spatiotemporal image correlation in prenatal diagnosis of isolated total anomalous pulmonary venous connection. Ultrasound Obstet Gynecol. 2007 Nov;30(6):830-7.

9.    International Society of Ultrasound in Obstetrics and Gynecology, Carvalho JS, Allan LD, Chaoui R, Copel JA, DeVore GR, Hecher K, Lee W, Munoz H, Paladini D, Tutschek B, Yagel S. ISUOG Practice Guidelines (updated): sonographic screening examination of the fetal heart. Ultrasound Obstet Gynecol. 2013 Mar;41(3):348-59. doi: 10.1002/uog.12403.

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