Introduction: An atrial septal aneurysm (ASA) is a rare congenital cardiac deformity characterized by interatrial septum protruding into atria forming a saccular structure.
Patient concerns: In our case, a 42-year-old female patient presented to our hospital complained of palpitation.
Diagnosis: Transthoracic echocardiography detected a 3.4 × 3.4 cm circular mass attached to the interatrial septum in right atrium complicated with a 6 mm secundum atrial septal defects (ASD).
Interventions: The patient received a cardiopulmonary bypass surgery to remove the mass and close the ASD.
Outcomes: The mass turned out to be an organized thrombus with calcium deposition and fibrinoid necrosis.
Conclusion: ASA is a potential location of atrial thrombus because of the stagnation of blood. Systemic embolism events are the main complications of ASA. Surgery or anticoagulation is both recommended in patients with ASA with thrombus.