Femoral versus antecubital vein contrast injection.

In their interesting narrative review about nontranspulmonary contrast echocardiography, Soliman et al. devoted a section to discuss the greater sensitivity of venous femoral injection of contrast for the detection of patent foramen ovale (PFO) as compared with venous brachial injection. This has been explained by intraatrial flow streaming, with inferior caval vein flow directed to the interatrial septum, whereas superior caval vein and coronary sinus flows are directed away from IAS. This interpretation is attractive as it matches foetal circulation, but in our opinion it has not been proved as the fundamental determining factor of the differences found between injection sites for PFO detection. Two widely cited papers specifically aimed to test the superiority of venous femoral injection for the diagnosis of right-to-left shunt, and demonstrated greater sensitivity of femoral versus brachial venous injection of contrast for shunt detection. In addition, Schuchlenz et al. found in a third study that semiquantitative shunt evaluation after femoral injection of contrast correlated better with balloon-sized PFO diameter than after brachial injection. But none of these studies addressed specifically the grade of right atrial opacification after each injection modality. We think that greater right atrial opacification after femoral injection (owing to factors as cannula diameter and faster bolus circulation) could have played a role in the observed differences, thus being a potential confusing factor when assessing the weight of the different caval veins inflow patterns. Lindeboom et al. showed in a well-illustrated case report the right atrial stream of flows from