THE DILATED CORONARY SINUS

• The normal coronary sinus measures 1-3 mm.
• Dilatation of the coronary sinus may resemble an atrioventricular defect on gray scale imaging (1,2).
• Dilatation of the coronary sinus:

1.  Dilatation due to volume overload is usually due to a persistent left superior vena cava (SVC) draining into it (3).

  -  Persistent left SVC is found in 0.1%-0.2% of autopsies of the general population (4) and in 2% of patients with acquired heart defect

undergoing angiography (5).
  -  Persistent left SVC draining into the coronary sinus is found in 4% of patients undergoing angiography (5) and 9% of autopsy cases with

congenital heart defects (4).
  -  Anomalous pulmonary venous drainage into the coronary sinus is less common (6).
  -  A coronary (7) or ventricular fistula (8) draining into the coronary sinus is less common and has not been described antenatally.

2.    Dilatation due to pressure overload is usually related to stenosis of the ostium, which, if congenital, is also associated with a persistent left SVC. In such cases the left superior vena cava would drain away from the heart (9).

• Dilatation may be seen in fetuses with IUGR and the velocities and waveforms may be more easily seen than in the coronary arteries.
• Pitfall in the diagnosis of dilated coronary sinus – atrioventricular septal defect (10). The Eustachian valve, which attaches to the edge of the coronary sinus ostium should provide an anatomical landmark and prevent confusion with an ostium primum atrial septal defect.

REFERENCES

1. Park JK, Taylor DK, Skeels M et.al. Dilated coronary sinus in the fetus: misinterpretation as an atrioventricular canal defect. Ultrasound Obstet Gynecol 1997;10:126-129.
2. Chaoui R. The fetal coronary system in prenatal diagnosis. Ultrasound Obstet Gynecol 1996;8 (Suppl):158.
3. Rein AJJT, Nir A, Nadjari M. The coronary sinus in the fetus. Ultrasound Obstet Gynecol 2000;15:468-472.
4. Nsash EN, Moore GW, Hutchins GM. Pathogenesis of persistent superior vena cava with a coronary sinus connection. Pediatr Pathol 1991;11:261-269.
5. Parikh SR, Prasad K, Lyer RN et.al. Prospective angiographic study of the abnormalities of systemic venous connections in congenital and acquired heart disease. Cathet Cardiovasc Diagn 1996;38:379-386.
6. Papa M, Camesasca C, Santoro F et.al. Fetal echocardiography in detecting anomalous pulmonary venous connection. Br Heart J 1995;73:355-358
7. Hipona FA. Congenital coronary arterial fistula to a persistent left superior vena cava. Am J Roentgenol Radium Ther Nucl Med 1996;97:355-358
8. Rein AJJT, Gillis RA, Moser AM et.al. Left ventricular to coronary sinus fistula. An echocardiographic diagnosis. In J Cardiol 1995;51:100-102
9. Gerlis LM, Gibbs JL, Williams GJ et.al. Coronary sinus orifice atresia with persistent left superior vena cava. A report of two cases, one associated with atypical coronary artery thrombosis. Br Heart J 1984;52:648-653
10. Park JK, Taylor DK, Skeels M et.al. Dilated coronary sinus in the fetus: misinterpretation as an atrioventricular canal defect. Ultrasound Obstet Gynecol 1997;10:126-129.