Opening of the Foramen Ovale After the Closure of Sinus Venosus Atrial Septal Defect

To the Editor, Foramen ovale (FO) is not a true deficiency of atrial septal tissue, but rather a potential space or separation between the septum primum and septum secundum located in the anterosuperior portion of the atrial septum.[1] At birth, the left atrial pressure exceeds the right atrial pressure due to respiration and forces the septum primum against the septum secundum and functionally closes the FO. This letter highlights the opening of the FO after the surgical closure of the sinus venosus atrial septal defect (SVASD) due to the stretching of the superior limbic band of septum secundum. A 20-year-old female presented with history of exertional dyspnea for the past 2 years. Her transthoracic echocardiographic examination revealed the diagnosis of 17 mm superior type SVASD with left-to-right shunting, moderate pulmonary hypertension, and partial anomalous pulmonary venous connection of the right upper pulmonary vein to the superior vena cava-right atrium junction. In the operation room, general anesthesia was induction and heart was examined using an adult transesophageal echocardiography (TEE) probe (6VT-D; Vivid E95; GE health care). The pre-cardiopulmonary bypass (CPB) TEE examination confirmed the preoperative transthoracic echocardiographic findings, and no additional atrial septal defect or FO was seen [Figure 1a and b]. After adequate heparinization, CPB was instituted and heart was arrested in diastole using blood cardioplegia. The surgical procedure executed was closure of the atrial septal defect and rerouting the right upper pulmonary vein to the left atrium. Post-CPB TEE examination unmasked the FO of 9 mm2 area shunting left-to-right [Figure 1c and d; Video 1] with a peak gradient of 1.5 mm Hg. The CPB was reinstituted, and direct closure of the FO was performed. Patient was weaned from CPB with Inj. Dobutamine 2.5 mcg/kg/min. Her postoperative period was uneventful.Figure 1: (a) Pre-cardiopulmonary bypass transesophageal echocardiographic midesophageal high bicaval view showing superior vena cava type sinus venosus atrial septal defect shunting left-to-right; (b) Pre-cardiopulmonary bypass transesophageal echocardiographic midesophageal bicaval view (color compare) showing no patent foramen ovale or additional ostium secundum atrial septal defect; (c) Post-cardiopulmonary bypass transesophageal echocardiographic midesophageal bicaval view (color compare) showing left-to-right shunt across the foramen ovale (yellow arrow); (d) Three-dimensional color Doppler dual-crop view of the interatrial septum (seen from the left and right atrial side) shows left-to-right shunting of the foramen ovale (red arrow). Abbreviations: - 3D, three-dimensional; ASD, atrial septal defect; AV, aortic valve; IAS, interatrial septum; LA, left atrium; ME, midesophageal RA, right atrium; RV, right ventricle; SVC, superior vena cava; TEE, transesophageal echocardiography {"href":"Single Video Player","role":"media-player-id","content-type":"play-in-place","position":"float","orientation":"portrait","label":"Video 1","caption":"","object-id":[{"pub-id-type":"doi","id":""},{"pub-id-type":"other","content-type":"media-stream-id","id":"1_iz4zm6qf"},{"pub-id-type":"other","content-type":"media-source","id":"Kaltura"}]} The persistence of patent FO is usually found in 20%–34% of adults.[2] In many cases, the patent FO might be functionally patent and have a tunnel-like appearance, because the septum primum forms a flap like valve.[1] The relative differences in the left and right atrial pressure can result in intermittent shunting of blood across the FO. It is usually benign but has been implicated in serious conditions like paradoxical embolism and cryptogenic strokes.[3] In our case, after the surgical closure of larger SVASD, the altered atrial hemodynamics might have stretched the superior limbic band of the septum secundum and opened the FO, causing “stretched” PFO.[2] This case also emphasizes that minor defects like PFO may remain hidden due to the shunt across larger SVASDs. This phenomenon is analogous to the observations in smaller ventricular septal defects, which are often undetected by echocardiography in the preoperative period due to the presence of shunt across the larger ventricular septal defects.[4] These findings underscore the dynamic role of intraoperative TEE in vigilance and meticulous evaluation during the management of complex congenital heart defects, ensuring no defect goes unaddressed to optimize patient outcomes. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.