Pseudo pulmonary embolism in complex congenital heart disease

Two children (aged 12 and 14 yr) with a history of complex congenital heart disease presented with symptoms and signs suggestive of pulmonary embolism. Initial ventilation-perfusion lung scans showed normal, approximately equal ventilation to both lungs. Global reduction of perfusion to the right lung was observed in one and was observed in the left lung in the other patient. It was not possible to exclude a large, central embolus in either case. Due to complex cardiac anatomy, however, which included bilateral cavopulmonary anastomoses in the first patient and SVC-right pulmonary artery and right atrial-pulmonary artery anastomoses in the second, repeat scans were performed within a short period in each case with different injection sites, including the contralateral arm and a leg injection, respectively. In both patients, these follow-up scans showed a different perfusion agent distribution to each lung when compared to the initial scans. These results demonstrated that there was no evidence of pulmonary embolism in either case.