The electrocardiogram manifestations of atrial and ventricular septal defects before and after repair

Atrial septal defects (ASDs) and ventricular septal defects (VSDs) account for the majority of congenital heart disease and may remain clinically relevant from infancy into adulthood. Echocardiography is the gold standard for diagnosis and detailed anatomical assessment of these defects; however, the electrocardiogram (ECG) may provide additional pathophysiological and prognostic insights. This review summarizes ECG findings in ASD and VSD before and after repair, with respect to the effects of defect type, timing of intervention, and postoperative evolution of electrical disturbances. A structured literature search was conducted to identify studies reporting ECG or rhythm abnormalities before and after repair. In hemodynamically significant ASD, ECG changes before repair generally correlate with chronic right-sided chamber volume overload. Secundum defects present with right-axis deviation and incomplete right bundle branch block. Primum defects are mainly associated with left-axis deviation and atrioventricular conduction delay, whereas sinus venosus defects may present with sinus node dysfunction. After closure, right-sided overload markers may return to normal; however, persistent atrial arrhythmias and conduction-system lesions frequently occur. In VSD, preoperative findings may include a normal ECG in small restrictive defects, to left, right, or combined ventricular overload patterns when associated with elevated left ventricle preload or right ventricle afterload. After surgery, the ECG tends to reflect evolving conduction-system injury and late rhythm-related vulnerability, such as right bundle branch block, atrioventricular block, QTc prolongation, progressive PR/QRS widening, and late complete atrioventricular block. Future studies with standardized timing and outcome-related follow-up are warranted to solidify the clinical relevance of specific ECG findings.