Abstract
BACKGROUND: Paradoxical embolism (PDE) is a rare, underrecognized cause of acute coronary syndrome, occurring when a thrombus crosses an intracardiac defect into systemic circulation. Sinus venosus atrial septal defects (ASDs), often associated with partial anomalous pulmonary venous drainage, may manifest in adulthood with complications such as PDE. CASE SUMMARY: We describe a 52-year-old man presenting with non-ST elevation myocardial infarction. Coronary angiography showed a distal right coronary occlusion suggestive of embolic infarction. Transthoracic echocardiography with bubbles revealed a right-to-left shunt. Transesophageal echocardiography confirmed a sinus venosus ASD with partial anomalous pulmonary venous drainage. Surgical correction with intra-atrial baffle and ASD closure was successful. DISCUSSION: This case highlights the importance of considering PDE in myocardial infarction in the absence of risk factors. Multimodality imaging was key to diagnosis and guiding treatment. TAKE-HOME MESSAGES: PDE is an underrecognized cause of acute coronary syndrome mechanism. Structural heart defects must be ruled out in coronary embolism or cryptogenic myocardial infarction.