Beware of the importance of looking "all-around" when you are doing a "quick" echo when a baby is unstable, in the immediate postoperative period. (Poor image quality is part of the deal!)
The first two panels show no significant effusion. However, in the lower-most panel - angled more posteriorly - there is a localized collection of clot compressing right atrium and part of right ventricle. This was not recognized due to poor images. Chest was opened to cannulate for ECMO! Clot was noted in the pericardial space, compressing right atrium (Lower-most panel). Hemodynamic status improved when the clot was removed. ECMO was not necessary.
Newborn, s/p Arterial switch operation. 3 hrs postop.