Coronary sinus unroofing associated with congenitally corrected transposition of the great arteries: a case report.

Background: Congenitally corrected transposition of the great arteries (ccTGA) is a rare congenital heart defect that is frequently associated with ventricular septal defects (VSDs) and valvular abnormalities. Advanced cardiac imaging techniques are often needed for early detection and detailed study of potential complications during long-term follow-up in these patients. Case summary: A 20-year-old male, asymptomatic during regular follow-ups, with ccTGA, restrictive subpulmonary VSD, and mild pulmonary stenosis. Latest outpatient evaluations showed progressive biventricular dilation, particularly in the subpulmonary left ventricle. Advanced cardiac imaging, including magnetic resonance imaging (MRI), identified an imbalance in flow between pulmonary and systemic circulations, indicated by a Qp/Qs ratio of 2.6, which could not be attributed to the known restrictive VSD. Additionally, 4D-flow MRI sequences detected low-velocity interatrial flow in the lower atrial segment. Subsequent targeted cardiac computed tomography (CT) confirmed extensive unroofing of the coronary sinus, revealing an unrecognized shunt contributing to the patient's haemodynamic imbalance. Discussion: Coronary sinus unroofing is exceedingly rare and often clinically silent, complicating diagnosis. Advanced cardiac imaging (MRI, CT) plays a pivotal role in detecting such anomalies. This case underscores the challenges of diagnosing subtle shunts in complex congenital heart disease and highlights the importance of comprehensive imaging for timely intervention and management.