Clinical History The patient, who was born with a double outlet right ventricle, underwent ventricular septal and right ventricular outflow tract patch repair at age 2. At the age of 6, he developed a mild stenosis of his left pulmonary artery, a common late complication. He was treated with catheter dilation. A nuclear lung perfusion scan at age 9 revealed total left lung perfusion of 43% and total right lung perfusion of 57%. A surveillance cardiac ultrasound (Figure 1) at age 12 was non-diagnostic secondary to body habitus (BMI>30), and cardiac CT angiography (CTA) was requested.
Findings Cardiac CT demonstrated normal caliber of the entire main pulmonary arterial tree (Figure 2). The examination also clarified the morphology and patency of the remote double-outlet right ventricle (DORV) repair (not shown). The total radiation dose for the cardiac CT was lower than annual background radiation in Boston (Figure 3), and the entire study was completed in less than 10 minutes.
(Click on images to enlarge)
Figure 1: Color Doppler echocardiography demonstrates the main pulmonary artery bifurcation with turbulent flow. The right was visualized and measured 17mm, while the left was difficult to visualize, measuring approximately 15mm.
Figure 2: Double oblique CTA image in the plane of the main and branch pulmonary arteries demonstrates normal caliber pulmonary arteries without stenosis (main 2.3 x 2.0 cm; right 1.4 x 1.4 cm; left 1.3 x 1.3cm measured in double oblique short-axis). The angle of the left pulmonary artery is more acute than in normal patients, in part due to congenital conotruncal rotation.
Figure 3: Effective radiation doses from various sources.
Discussion DORV falls within the spectrum of conotruncal abnormalities that range from tetralogy of Fallot to complete transposition of the great arteries1. DORV is an uncommon congenital cardiac defect characterized by the morphologic right ventricle being the primary origin of both great arteries. A ventricular septal defect (VSD) is almost always present, although its location can be highly variable2. Patients with corrected DORV remain at risk for main, segmental, and branch pulmonary artery stenosis, and thus require ongoing surveillance studies.
This case demonstrates the complementary role of cardiac CT to traditional imaging modalities in the evaluation of complex congenital heart disease in carefully selected patients. Radiation exposure from these CT studies is modest with the implementation of advanced dose-reduction technologies such as high-pitch helical, prospectively triggered, low-voltage, dual-source CTA3.
Lev M.,Bharati S., Meng L., Liberthson R., Paul M., Idriss F. A concept of Double-Outlet Right Ventricle. Journal of thoracic and Cardiovascular surgery.64; 271-281.
Frank L, Dillman JR, Parish V, Mueller GC, Kazerooni EA, Bell A, Attili AK. Cardiovascular MR imaging of conotruncal anomalies. Radiographics. 2010 Jul-Aug;30(4):1069-94.
Engel LC, Ghoshhajra BB, Techasith T, Medina-Zuluaga H, Brady TJ, Kalra, M, et. al. The Evolution of Cardiac CT Dose Reduction at a Tertiary Academic Medical Center: A 5-year Experience. Abstract presented at the annual meeting of the Society of Cardiac Computed Tomography, Las Vegas, Nevada, July 15, 2010.
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