Evaluation of the Post-Shunt Status with Electron Beam Computed Tomography in Cyanotic Congenital Heart Disease

Abstract

The assessment of the accuracy of Electron Beam Computed Tomography (EBCT) for the follow-up of pulmonary vascular system after the shunt operation in cyanotic congenital heart diseases was purpose of the study. The study group consists of 16 consecutive patients with cyanotic congenital heart disease who had Blalock-Taussig (BT) shunt (n=7), bi-directional cavo-pulmonary shunt (BCPS, n=7) and unifocalization (n=2). EBT images were obtained on systolic phase under EKG gating and after intravenous administration of contrast agent. We evaluated the shunt patency, anatomy of intrapericardial pulmonary artery, parenchymal pulmonary vessels and background lung attenuation for the pulmonary blood flow, and the presence of systemic arterial and venous collaterals. Angiography (n=12) and echocardiography (n=16) were used as the gold standards. EBCT was consistent with angiogram in detecting the shunt patency and in depicting the anatomy of the intrapericardial pulmonary artery. Occlusion of the BT shunts was not detected in 2 patients by echocardiography. Diffuse or focally decreased pulmonary flow on EBCT in 8 patients was consistent with the pulmonary hemodynamics pattern revealed by cardiac catheterization. Uneven attenuation between lobes was related with multifocal supply of pulmonary flow or occlusion of lobar pulmonary arteries. Systemic collateral arteries were observed in 5 at the corresponding site of the decreased pulmonary flow. Systemic venous collaterals seen in all patients following BCPS were eventually draining to the inferior vena cava in 5 and to the left atrium in 2. EBCT provided accurate information of the pulmonary vascular system after shunt and has unique advantage over echocardiography in assessing patency of BT shunt or unifocalization tubes within the pleural space, the estimation of regional difference in pulmonary hemodynamics, and the detection of systemic collateral vessels. Therefore EBCT may provide useful information about the timing of definitive correction and the need for a second shunt or an interventional procedure prior to total repair.