Prevalence: Persistent left superior vena cava (Figures C,D ) has been observed in 0.3-0.5% of the general population^1,2 and in 1.5-10% of patients with congenital hear disease^2,3. The persistent left superior vena cava might be connected to the coronary sinus or to the left atrium. In cases of connection to the coronary sinus, this sinus is enlarged and opens into the right atrium (Figure B). In cases of connection to the left atrium, there is usually absence of the coronary sinus.

Etiology: During morphogenesis, the left common cardinal vein drains into the left portion of the sinus venosus, i.e., the coronary sinus. The LSVC obliterates in late embryonic or early fetal life. Failure of obliteration results in persistent left superior vena cava².

Associated anomalies: persistent left superior vena cava with coronary sinus connection should suggest an associated malformation, especially atrioventricular canal, cor triatriatum or mitral atresia^1-3.

Clinical implications of a coronary sinus dilatation: The anomaly may accidentally be discovered in healthy people and has also been reported in athletes with normal treadmill testing⁴.

The main adverse effects are^5,6:

1. Cardiac arrhythmia due to stretching of the atrioventricular node and bundle of Hiss

2. Obstruction of left ventricular flow because of partial occlusion of the mitral valve. The symptoms may increase due to left to right shunt across the atrial septum.

Week 15: "CLASSICAL" but false atrioventricular septal defect:  The AV valves are inserted “on the same line” (or common insertion of the valves) +  “absence of septum primum”. We get this false image (the section is inferiorposterior) because the the wall of the dilated coronary sinus masks the crux and mimics the “linear insertion of the valves” (in the clips it gives the illusion of the classical unstablefloating crux (Rastelli type A).  

The normal crux from superioranterior projection with the dilated coronary sinus. The posterior wall mimics the opening the flaps of the foramen ovale to the right atrium.

Week 18 Left parasagittal section through the mediastinum the entrance of the left SVC into the coronary sinus.  

There are 2 short video clips:

• demonstrating the flap in the right atrium due to the enlarged coronary sinus and

• the left parasagittal section through the mediastinum the entrance of the left SVC into the coronary sinus.
   

Sonographic findings: Imaging of the coronary sinus was reported in 97.4% of normal fetuses. The diameter of the coronary sinus ranged from 1 to 3.2 mm and correlated well with gestational age. In fetuses with persistent left superior vena cava, the dilated coronary sinus was approximately three times larger than a normal coronary sinus⁷.

Sonographic pitfalls: The ostium of the coronary sinus opens directly into the right atrium in close proximity to the insertion of the atrioventricular valves. If the coronary sinus is dilated, it can create the appearance of an atrioventricular canal defect (figure A). Park et al.⁸ presented three cases in which the correct diagnosis avoided an unnecessary termination of pregnancy.

References

1.      Biffi M, Boriani G, Frabeti L, Bronzetti G, Branzi A. Left superior vena cava persistence in patients undergoing pacemaker or cardioverter-defibrillator implantation: a 10-year experience. Chest 2001;120:139-144.

2.      Perloff JK. Congenital anomalies of vena caval connection. In: The Clinical Recognition of Congenital Heart Disease 4th Ed. WB Saunders Company. 1994:703-714.

3.      Nsah EN, Moore GW, Hutchins GM. Pathogenesis of persistent left superior vena cava with a coronary sinus connection. Pediatr Pathol 1991;11:261-269.

4.      Kinoshita N, Hasegawa K, Oguma Y, Katsukawa F, Onishi S, Yamazaki H. Fortuitously discovered persistent left superior vena cava in young competitive athletes. Clinical implications of sports physicians. J Sports Med Phys Fitness 2001;41:275-277.

5.      Cochrane AD, Marath A, Mee RB. Can a dilated coronary sinus produce left ventricular inflow obstruction? An unrecognized entity. Ann Thorac Surg 1994;58:1114-1116.

6.      Benatar A, Demanet H, Deuvaert FE. Left-ventricular inflow obstruction due to a dilated coronary sinus mimicking Cor Triatriatum. Thorac Cardiovasc Surg 1999;47:127-128.

7.      Rein AJ, Nir A, Nadjari M. The coronary sinus in the fetus. Ultrasound Obstet Gynecol 2000;15:468-472.

8.         Park JK, Taylor DK, Skeels M, Towner DR. Dilated coronary sinus in a fetus: misinterpretation as an atrioventricular canal defect. Ultrasound Obstet Gynecol 1997;10:126-129