Interatrial septum patency - Clinical implication of a grading system based on cardiac computed tomography

Background: Cardiac computed tomography angiography (CTA) has been shown to be an excellent modality not only to assess the coronary arteries but also the interatrial septum. We aimed to develop a classification system to grade interatrial septal patency with a focus on clinical applicability. Methods: Patients who underwent cardiac CTA from January 1st, 2018 to December 31st, 2022 at a specialized imaging center were included into a registry study. Scans were acquired on a third-generation dual-source CT scanner and retrospectively analyzed using a dedicated post-processing software. Results: A total of 11053 CT scans were performed of which 10270 were included in the final study. Incorporating septal morphology and patency, a four-level grading system was created classifying interatrial septal patency (IASP) from I to IV. Patients without evidence of interatrial left to right contrast agent (CA) flow had either a smooth septum in 5246 cases (IASP I, 51%) or a closed flap in 2620 cases (IASP II, 26%). An open flap with a clearly detectable CA jet was found in 2086 patients (IASP III, 20%) and a potentially significant shunt in 318 patients (IASP IV, 3%). Applying this grading system to the present study population might have reduced the need for further invasive confirmatory examinations, namely transesophageal echocardiography, by 71% (IASP I and IASP III, respectively). Conclusions: Cardiac CTA is a suitable technique for interatrial septum analysis that might help to guide clinical pathways and reduce the rate of additional invasive examinations.