Incidentally Discovered Adult Congenital Heart Disease in a Patient With Decompensated Heart Failure.

Cor triatriatum is a rare congenital heart defect that divides the right or left atrium into three chambers. Although the diagnosis is typically made within the first years of birth, it can occasionally be made later in adulthood and is frequently associated with other cardiac defects but may be present in isolation. Clinical manifestations range from lung congestion, exhaustion, coughing, and dyspnea to the onset of heart failure. The treatment depends on the existence of symptoms; asymptomatic patients need only regular follow-up, while symptomatic patients require intervention either surgically or percutaneously. We present a case of an adult patient who presented to us with a manifestation of decompensated right-sided heart failure, and upon investigation, we incidentally discovered that she had a rare congenital heart defect, a non-fenestrated isolated cor triatriatum dexter (CTD) not associated with the tricuspid valve defect or other congenital heart defects. Right-sided heart failure has developed as a complication of CTD. Additionally, this case highlights the diagnostic value of transthoracic echocardiography in adult congenital heart disease.