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.