Case Report: Cor triatriatum sinister presenting as acute decompensated heart failure in an adolescent

Background Cor Triatriatum sinister (CTS) is a rare congenital cardiac anomaly caused by a fibromuscular membrane subdividing the left atrium, potentially leading to impaired left ventricular inflow, pulmonary venous hypertension, and heart failure. Clinical presentation is highly variable and may mimic primary respiratory disease, resulting in delayed diagnosis, particularly in older children and adolescents. Case Summary A 13-year-old previously healthy boy presented with acute hypoxic respiratory failure following one week of progressive exertional dyspnea. Initial findings of elevated jugular venous pressure and bilateral pulmonary congestion with low inflammatory markers suggested a cardiogenic etiology. Bedside lung ultrasonography demonstrated diffuse pulmonary oedema, and transthoracic echocardiography revealed a severely obstructive supramitral membrane consistent with cor Triatriatum sinister and secondary pulmonary hypertension. After stabilization with noninvasive ventilation and diuresis, the patient underwent minimally invasive surgical excision of the accessory membrane, resulting in complete relief of obstruction. Postoperative recovery was uneventful, with sustained clinical and echocardiographic improvement on follow-up. Discussion This case illustrates the diagnostic challenge posed by CTS when presenting outside infancy and highlights the importance of early cardiac evaluation in pediatric patients with atypical respiratory presentations. Prompt use of bedside ultrasound and echocardiography enabled timely diagnosis and definitive management, leading to an excellent outcome. Conclusion CTS, although rare, should be considered in children and adolescents presenting with unexplained pulmonary oedema or hypoxemia. Early recognition and surgical correction are associated with excellent short- and long-term outcomes.