Investigations
Electrocardiogram revealed atrial fibrillation, which reverted spontaneously to sinus rhythm. Transthoracic echocardiogram revealed a large ostium secundum atrial septal defect (ASD), 41x42mm in size, with left-to-right shunt, pulmonary hypertension (60mmHg) and dilatation of the right ventricle. Computed tomography (CT) scan showed: (1) a persistent left superior vena cava (LSVC) draining into the left atrium (LA) in close proximity to the left atrial appendage, (2) the absence of a left brachiocephalic vein, (3) the abnormal independent drainage of the coronary veins in the LA. The great cardiac vein drained into the postero-lateral wall, the marginal vein into the lower wall and two middle cardiac veins into the medial-lower wall of the LA (Fig. 1; Fig 2). Cardiac catheterisation confirmed pulmonary hypertension (pulmonary arterial pressure 70/44mmHg; mean 45mmHg, wedge pressure 14mmHg), arterial SpO2 91%, systemic venous saturation 70% and pulmonary artery saturation 90%, Qp/Qs 2.8. Nitric oxide caused a significant reduction of pulmonary artery and wedge pressures, with an increment of the Qp/Qs to 11.5. The patient was referred and accepted for elective surgery.