Dilated coronary sinus in the fetus: misinterpretation as an atrioventricular canal defect

The ostium of the coronary sinus opens directly into the right atrium in close proximity to the insertion of the atrioventricular values. If the coronary sinus is dilated, it can create the appearance of atrioventricular canal defect in the fetal echocardiographic four-chamber view. The diagnosis of a serious heart lesion, such as a canal defect, necessitates decisions regarding pregnancy termination or optimal timing/location of delivery. We present three women who were referred at 23, 36 and 38 weeks' gestation with a preliminary diagnosis by level II ultrasound of a fetal atrioventricular canal defect. In each patient, the targeted fetal echocardiogram demonstrated a dilated coronary sinus and no evidence of an atrioventricular canal defect. The fetal echocardiographic presentation of a dilated coronary sinus can be mistaken for an atrioventricular canal defect. Misdiagnosis can be avoided by utilizing both variable angulation in the four-chamber projection and additional transducer views to confirm an intact atrioventricular septum and two normal atrioventricular valves.