Clinical Significance of Interatrial Septal Thickening: A Retrospective Study

Background: Increased interatrial septal (IAS) thickness is commonly observed on transesophageal echocardiography, but its prognostic significance remains unclear. IAS adiposity has been linked to aging and obesity; however, whether septal thickening is associated with mortality or cardiac rehospitalization remains unknown. Objectives: To evaluate whether IAS thickness is associated with four-year mortality, cardiac rehospitalization, and clinical, metabolic, echocardiographic, and electrocardiographic characteristics. Methods: In this retrospective study, we analyzed 1008 adults who underwent transesophageal echocardiography from January 2020 to July 2021. IAS thickness was measured in the bicaval view. Kaplan–Meier analysis and Cox models assessed four-year mortality and cardiac rehospitalization, adjusting for age, sex, body surface area, coronary artery disease, diabetes, and prior stroke. Multivariable logistic regression evaluated associations between IAS thickness and clinical, metabolic, and echocardiographic variables. Results: IAS thickness ≥ 10 mm was present in 150 patients (15%). IAS thickening was not significantly associated with mortality (p = 0.10) or cardiac rehospitalization (p = 0.11). IAS thickness was independently associated with older age, higher body surface area, diabetes, low HDL cholesterol, carotid artery disease, oral corticosteroid use, and smoking (all P ≤ 0.05). No independent associations were identified between IAS thickness and structural or electrocardiographic abnormalities. Conclusions: IAS thickening is not independently associated with four-year mortality or cardiac rehospitalization and appears to reflect systemic cardiometabolic remodeling rather than adverse cardiac structural or electrical abnormalities. These findings support IAS thickening as a generally benign anatomic variant linked to metabolic risk rather than a determinant of adverse clinical outcomes.