Diagnostic Value of the Terminal D1S + D3R Pattern for Detecting Right Ventricular Dilatation in Patients with Atrial Septal Defect

Background: Atrial septal defect (ASD) is common in adults and may cause chronic right ventricular (RV) volume overload and remodeling. Electrocardiography (ECG) may serve as a screening adjunct to echocardiography. Objectives: To evaluate the association of the terminal D1S + D3R ECG pattern, defined as a terminal S wave in lead I plus a terminal R wave in lead III, with structural and hemodynamic right heart involvement in adult secundum ASD. Methods: A total of 161 adult patients with secundum ASD were retrospectively analyzed. Right heart involvement was assessed using pulmonary-to-systemic flow ratio (Qp/Qs) ≥ 1.5 and a right ventricular/left ventricular (RV/LV) ratio > 1. ECG parameters, including right bundle branch block (RBBB), right axis deviation, V1–V2 R-wave positivity, and terminal D1S + D3R, were evaluated by two blinded cardiologists, with final classifications determined by consensus. Multivariable Firth penalized logistic regression, correlation analyses, and receiver operating characteristic (ROC) analyses were performed. Results: In the multivariable Firth penalized logistic regression model, pulmonary artery pressure (PAP) and ASD diameter were independently associated with Qp/Qs ≥ 1.5, whereas the terminal D1S + D3R pattern was not. The terminal D1S + D3R pattern was independently associated with RV dilatation after adjustment for age, sex, PAP, and ASD diameter (odds ratio [OR]: 9.90, 95% confidence interval [CI]: 2.82–38.20, p < 0.001) and showed good discriminatory performance for RV dilatation (area under the curve [AUC]: 0.881, 95% CI: 0.831–0.932). Conclusions: In adults with secundum ASD, a positive terminal D1S + D3R ECG pattern is independently associated with RV dilatation and may serve as a practical adjunctive screening marker. However, it should not replace echocardiographic assessment.