When an Atrial Septal Defect Is No Longer Silent: A Case Report of a Large Symptomatic Defect Presenting in Adulthood

Atrial septal defects (ASDs) are among the most common forms of congenital heart disease diagnosed in adulthood. Ostium secundum defects represent the majority of cases and may remain clinically silent for decades. Delayed diagnosis can lead to progressive right-sided cardiac chamber dilation, pulmonary hypertension, arrhythmias, and heart failure. The choice between percutaneous and surgical closure depends on anatomical characteristics such as defect size and the adequacy of surrounding septal rims. We report the case of a 49-year-old woman with hypertension, type 2 diabetes mellitus, and hyperlipidemia who presented with one week of substernal chest pain, palpitations, and progressive dyspnea on exertion consistent with New York Heart Association (NYHA) functional class III limitation. Physical examination revealed a holosystolic murmur best heard along the tricuspid area with inspiratory accentuation. Transthoracic echocardiography identified a large secundum ASD measuring 35 mm × 22 mm with elevated pulmonary artery systolic pressure and right-sided chamber dilation. Transesophageal echocardiography confirmed a large defect with minimal aortic rim and limited atrioventricular valve rim, precluding percutaneous closure. Cardiac catheterization demonstrated bidirectional shunting with a Qp/Qs ratio of 2.65 and normal pulmonary vascular resistance. The patient subsequently underwent successful surgical ASD closure using a bovine pericardial patch. Her postoperative course was uncomplicated, with complete resolution of symptoms and normalization of pulmonary artery pressures on follow-up echocardiography six months later. This case highlights the potential for large ASDs to remain undiagnosed until adulthood, when progressive right-sided cardiac remodeling leads to symptomatic disease. Early detection through timely echocardiographic evaluation is critical to facilitate timely intervention and may expand eligibility for less invasive percutaneous repair. Prompt recognition and closure of hemodynamically significant ASDs can prevent irreversible cardiopulmonary complications and significantly improve long-term outcomes.