British Journal of Radiology (2006) 79, e5-e7
© 2006 British Institute of Radiology
doi: 10.1259/bjr/47408749
Diagnosis of tetralogy of Fallot with anatomically corrected malposition of the great arteries and single coronary artery by multidetector CT
A Khositseth, MD
1
R Pornkul, MD
2 and
S Siripornpitak, MD
2
1 Division of Pediatric Cardiology, Department of Pediatrics, 2 Department of Radiology, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok 10400, Thailand
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Abstract
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We present a case of an 8-year-old boy diagnosed as a tetralogy of Fallot with anatomically corrected malposition of the great arteries by echocardiography and cardiac catheterization. Multidetector CT nicely elucidated the course of the single coronary artery from the right coronary cusp, which traverses across the right ventricular outflow tract.
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Introduction
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An 8-year-old boy presented with dyspnoea on exertion and mild cyanosis. Physical examination revealed mild central cyanosis with oxygen saturation of 80%, clubbing of fingers, single S2 with increased intensity and grade 3/6 systolic ejection murmur at left upper sternal border. Electrocardiography (ECG) demonstrated right axis deviation and right ventricular hypertrophy. ECG showed a large subaortic ventricular septal defect (VSD) with an overriding aorta (<50%), mitral-aortic valve continuity, right ventricular hypertrophy, severe infundibular and valvular pulmonary stenosis (PS), and the aorta is parallel to and left of the pulmonary artery. The coronary arteries were not well visualized. Cardiac catheterization confirmed the anatomical findings detected by echocardiography and, in addition, demonstrated a single coronary artery arising from the right coronary cusp, which supplied both right and left coronary arteries. The diagnosis of tetralogy of Fallot with anatomically corrected malposition of the great arteries and single coronary artery was therefore made.
To better delineate the course of the coronary arteries, CT angiography (CTA) of the coronary arteries was performed with a 4-slice multidetector CT (MDCT) (Light Speed Plus; GE, Milwaukee, WI) in the retrospective ECG gated mode, axial plane using 1.25 mm collimation, 1 mm reconstruction interval at 75% of the R-R interval, covering the level from carina to cardiac apex. Respiratory effort was suspended by the anaesthetist for the 17 s data acquisition. Non-ionic contrast media injection via the peripheral vein was introduced at a dose of 2 ml kg–1 and a rate of 2 ml s–1. The scan started 20 s after injection of the contrast media. Post-processing three-dimensional volume rendering and multiplanar reformation images were acquired by GE Medical System software (Volume Analysis Vox two 3.0.26e). This revealed subvalvular and valvular PS, large subaortic VSD (Figure 1
), overriding of the aorta and aortic-mitral valve continuity (Figure 2). The great arteries originated above the appropriate ventricles, although there was some degree of overriding of the aorta over the VSD. Moreover, their spatial relationships were abnormal in that the aorta was anterior to and left of the pulmonary artery (Figures 1 and 3). Figure 3 demonstrated a single coronary artery from the right coronary cusp. The left coronary artery (LCA) courses to the left normally, dividing into the left anterior descending and the left circumflex arteries running along the interventricular groove, and then along the left atrium posteriorly, respectively. The right coronary artery (RCA) courses to the right and normally divides into two branches, one along the right atrioventricular groove and the other along the surface of the right ventricle. However, the course of the RCA, which is normal, traverses the right ventricular outflow tract. In contrast, the abnormal LCA from the right coronary cusp traverses to the left, but not across the right ventricular outflow tract.
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Figure 1. Coronal multiplanar reconstruction from CT angiography with a 1.25 mm slice thickness and cardiac gating technique demonstrates findings compatible with tetralogy of Fallot [right ventricular hypertrophy, right ventricular outflow tract obstruction (#), ventricular septal defect (*)]. The aorta (AO) is to the left of the pulmonary artery (PA). LV, left ventricle; RV, right ventricle.
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Figure 2. Oblique coronal multiplanar reconstruction from CT angiography with a 1.25 mm slice thickness and cardiac gating technique demonstrates the fibrous continuity between the mitral and aortic annuli (bold arrows), a large subaortic ventricular septal defect (*) and overriding of the aorta (AO). AV, aortic valve leaflets; MV, mitral valve leaflets as shown by dash arrow; LV, left ventricle; and RV, right ventricle.
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Figure 3. Volume-rendered 3D reconstruction of the heart and great vessels from multidetector CT demonstrates the aorta (AO) located anterior and leftward to the pulmonary artery (PA). Single coronary artery comes off the right coronary cusp. RCA, right coronary artery; LCA, left coronary artery; LCX, left circumflex artery; LAD, left anterior descending artery; RA, right atrium; RV, right ventricle; and LV, left ventricle.
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Discussion
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Anatomically corrected malposition of the great arteries (ACMGA) is a rare form of conotruncal malformation in which the aorta and pulmonary artery arise from their appropriate ventricles despite the presence of malposition of the great arteries (S,D,L) [1]. The frequent associated anomalies are valvular and subvalvular pulmonary stenosis. This case report described tetralogy of Fallot associated with ACMGA and single coronary artery. Although the echocardiography and cardiac catheterization can elucidate almost all important findings, the exact course of the coronary arteries is so crucial in determining the best possible technique of surgical repair to avoid injuring the right coronary artery. In the repair of a tetralogy of Fallot (TOF), a transannular pericardial patch along with patch closure of the VSD is needed. The repair is technically difficult in this patient because the path of the RCA anterior to the pulmonary trunk virtually precludes a transannular patch repair. Pulmonary valvulotomy and/or infundibulectomy have been performed in the majority of reported patients with ACMGA, but incomplete relief of the obstruction occurred in some patients [2–4], which required a conduit repair from the right ventricle to the pulmonary artery [2]. There was a report that a leftward deviation of the RCA away from the right atrioventricular groove associated with a levoposition of the anterior aorta allowed successful transannular subpulmonary incision of the right ventricular outflow tract along the right atrioventricular groove without jeopardizing the RCA [5]. However, the anatomical orientation of the RCA to the right ventricular outflow tract is still the main concern. In this case, the course of the RCA (which normally arises from the right coronary cusp, traverses across the right ventricular outflow tract) potentially hinders the transannular patch repair technique. Finally, this patient underwent patch closure of the VSD and pericardial valve conduit with valve ring of 20 mm connected between the right ventricle and the main pulmonary artery to avoid any injury to the RCA and its branches. He had uneventful surgery with a discharge echocardiography demonstrating no residual VSD and mild residual pulmonary stenosis with a pressure gradient of 21 mm Hg and mild pulmonary regurgitation.
MDCT is new technology, which can be performed safely even in small infants. It provides clear information pertinent to great vessels and coronary arteries and has been proven to be very useful in delineating the complex cardiac anatomy non-invasively in this patient. On the other hand, magnetic resonance angiography (MRA) of the coronary arteries is another useful technique in the evaluation of coronary arteries in congenital heart disease [6]. The major advantage of MRA, particularly in children, is no exposure to ionizing radiation and the fact that it does not involve the use of contrast media which may cause adverse reaction such as renal impairment. However, MRA is technically more difficult and time consuming than MDCT. More importantly, in comparison with MDCT, MRA offers less spatial resolution. Lastly, the availability of the coronary MRA software is not as widely available as MDCT. Therefore, MDCT is a more feasible and applicable tool of investigation in most circumstances.
In conclusion, MDCT may be able to replace cardiac catheterization in the assessment of coronary artery anatomy. As illustrated in this patient, MDCT, in combination with echocardiography, provides an excellent, non-invasive method of obtaining detailed images required for planning in the management of this complex cardiac anatomy.
Received for publication January 14, 2005.
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References
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Abstract
Introduction
