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

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.

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.

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).

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.