FIG 30.7 Heart exhibiting postnatal persistence of the valves of the embryonic venous sinus Unlike the heart shown in Fig 30.6, the valves have not become fenestrated, so they produce a partition between the systemic venous sinus and the appendage of the morphologically right atrium In this heart, however, there is coexisting tricuspid atresia due to absence of the right atrioventricular connection so that the partition merely exaggerates the flow of blood from the inferior caval vein to the patent oval fossa The hemodynamic effect of the partition itself is of little significance since the blood is required to cross the oval fossa, and the persistent valve augments this pattern of flow The opening of the superior caval vein, however, may not be included within the partitioned venous sinus (see Fig 30.7) The lesion is of more significance when the tricuspid and pulmonary valves are patent The persisting valve can then become aneurysmal and protrude into the right ventricle like a windsock (Fig 30.8) FIG 30.8 Windsock removed from a patient whose valves of the embryonic venous sinus had become aneurysmal and herniated through the tricuspid valve, obstructing the flow of blood through the right side of the heart Surgical removal is easy once diagnosis has been made.10 Diagnosis is now readily made using cross-sectional echocardiography (Fig 30.9), although the aneurysmal valve does not always produce symptoms and can be a chance finding.11 FIG 30.9 Cross-sectional echocardiogram showing division of the morphologically right atrium produced by persistence of the valves of the embryonic systemic venous sinus LA, Left atrium; LV, left ventricle; RA, right atrium; RV, right ventricle (Courtesy Dr I.B Vijayalakshmi, Sri Jayadeva Institute of Cardiovascular Sciences and Research, Bangalore, India.)