A Case of Atypical Cor Triatriatum Sinister Persisting into Adulthood

<i>Background:</i> Cor-triatriatum is a rare congenital cardiac anomaly characterized by a fibromuscular membrane that divides the left atrium into two chambers, giving the appearance of three atrial compartments. It typically presents during infancy or childhood due to obstructive symptoms but may remain undiagnosed until adulthood in milder or non-obstructive cases. <i>Case Presentation:</i> A 33-year-old Ethiopian male with no known past medical history presented with a one-month history of progressive shortness of breath, orthopnea, paroxysmal nocturnal dyspnea, and bilateral leg swelling. He also reported a productive cough, pleuritic chest pain, and high-grade intermittent fever of similar duration. Physical examination and initial investigations suggested decompensated heart failure and pneumonia. Transthoracic echocardiography revealed findings consistent with cor-triatriatum sinister. Despite initiation of supportive care, intravenous antibiotics, diuretics, and mechanical ventilation, the patient’s condition deteriorated. He ultimately developed cardiogenic shock and died during hospitalization. <i>Conclusion:</i> Cor-triatriatum is a rare but important cause of heart failure in adult patients. This case demonstrates that congenital heart disease can remain clinically silent for decades and may present with acute decompensation. Awareness and early recognition of this anomaly, especially in resource-limited settings, are essential for timely diagnosis and management. Point-of-care ultrasound can be a valuable tool in such environments for rapid cardiac assessment and should be considered when evaluating patients with unexplained heart failure symptoms.