Background The coronary sinus is a venous system situated at the back of the atrioventricular junction and draining into the right atrium, which can be assessed from various echocardiography angles. In certain cases, the coronary sinus can be dilated by volume or more rarely by pressure overload.

Objectives To evaluate the efficacy of detecting coronary sinus in neonates and to determine the standard values of coronary sinus measurements. To highlight the importance of functional echocardiography in the assessment of the causes of dilation.

Methods Screening with echocardiography was done in 30 neonatal patients who were admitted to our unit (median 34-week gestation). Coronary sinus was evaluated in the four-chamber view (83% of cases), subcostal view (8%) or parasternal short-axis view (12%). The second group of two patients with a dilated coronary sinus was compared with the normal group.

Results Adequate coronary sinus imaging was done in 97.4 per cent of normal neonates. The diameter of the coronary sinus varied from 1 mm to 3.4 mm. The two neonates with a dilated coronary sinus had a persistent left superior vena cava, which flowed into it. In the abnormal group, the diameter of the coronary sinus was nearly three times greater. CS should be assessed and indexed to the body surface area as part of standard echocardiography screening. The dilated coronary sinus (+2 Z score) has several causes, including persistent left superior vena caves in our case, a total anomaly in the pulmonary venous drainage, pathological hepatic venous drainage or sinus ASD. A thorough evaluation of the Right Ventricle (RV) function is required, as dilated CS is one of the characteristics of RV dysfunction.

Conclusions Dilated CS can be contributed by many factors and detailed imaging is recommended, in a few patients, a contrast echo can help in visualising in details CS and rule out deroofing.