Sustained Monomorphic Ventricular Tachycardia Decades After Ventricular Septal Defect Repair

BACKGROUND: Ventricular tachycardia can occur decades after ventricular septal defect repair, but surface electrocardiogram (ECG) and noninvasive imaging cannot prove patch-dependent reentry. CASE SUMMARY: A 57-year-old man with ventricular septal defect patch repair in infancy and no adult congenital heart disease follow-up presented with chest pain, dyspnea, and near-syncope. ECG showed sustained monomorphic ventricular tachycardia at 209 beats/min. Transthoracic echocardiography showed left ventricular ejection fraction 30%, right ventricular dysfunction, moderate-to-severe tricuspid regurgitation, and possible right ventricular thrombus. Transesophageal echocardiography demonstrated fixed postoperative-appearing tissue rather than thrombus. Coronary angiography showed no obstructive disease. After cardioversion, a secondary-prevention dual-chamber implantable cardioverter-defibrillator was placed, and sotalol was initiated with renal and ECG monitoring. DISCUSSION: The case provides a framework for suspected but unproven postoperative scar-related ventricular tachycardia by separating substrate plausibility from circuit proof. TAKE-HOME MESSAGE: Repaired ventricular septal defect carries lifelong arrhythmic risk; patch dependency requires electroanatomic mapping, whereas prevention decisions should follow clinical risk.