Multi-detector computed tomography and spiral CT are widely used in diagnosis of thoracic aortic diseases. A CT scan is simple, non-invasive, and quick. Contrast administration adds more information about cardiovascular system and extra-cardiac vasculature and thoracic structures like tracheal and esophageal abnormalities [4, 6].
In the current study, all patients were sedated by chloral hydrate (50–100 mg/kg; maximum dose, 2000 mg) apart from one case aged 9 years who responded well to verbal instructions. No sedation-related complications were encountered in the study. This was the same as Kimura-Hayama et al. [7] (Figs. 3, 4, and 5).
Cases with aortic coarctation were correctly described as regards coarctation segment length, location, extend of stenosis, and extent of collaterals formation using axial, sagittal oblique MIP, volume-rendered images. Percentage of stenosis was calculated but it is not useful for visualizing the aortic gradient which agreed with Chen et al. [8] Türkvatan et al. [9], and Al-Azzazy et al. [10].
In this study, the length of the coarctation was short in 9 cases (81.8%) and long in 2 cases (18.8%). The length of the coarctation was considered short if the length of the narrowed aortic segment was less than 5 mm and long if the length of the narrowed aortic segment was more than 5 mm. These percentages are nearly the same as Türkvatan et al. [9], and slightly less than that of Al-Azzazy et al. [10] and Ahmed et al. [11] who had a higher percentage for short segment coarctation patients.
As regards vascular rings detected, Echo and MDCT had 50% and 100% sensitivity respectively for detection of vascular rings when compared to conventional angiography. The detected types of vascular rings were double aortic arch with right arch predominance and right side aortic arch with aberrant left subclavian which was consistent with Hamisa et al. [12] who concluded that double aortic arch and right side aortic arch with aberrant left subclavian were the commonest forms of vascular rings in their study with 100% sensitivity for MDCT in vascular rings detection.
Interrupted aortic arch (IAA) type B was the final diagnosis of two cases in this study with percentage of 6.6% which is close to percentage described by Chen et al. [8] who detected IAA percentage of 8.8% and El Dien et al. [13] who detected the same percentage of IAA type B among his cases. MDCT had 100% sensitivity for interrupted arch detection; echocardiography showed 50% sensitivity when compared to conventional angiography results.
Jia et al. [14] confirmed the importance of MDCT in detection of major aorto-pulmonary collaterals (MAPCAs) as they found that MDCT has the potential to replace preoperative catheterization as they found excellent anatomy agreement between MDCT and surgery.
In the current study, echocardiography missed detection of one case with MAPCAs which was correctly detected by MDCT and conventional angiography; this agreed with Nakhla et al. [15] who described lower echocardiography sensitivity for MAPCAs detection.
In this study, different aortic arch sidedness and branching patterns were described and their presence in association with different thoracic aortic pathologies was assessed using MDCT as a preoperative planning tool and was found that:
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Left-sided aortic arch with aberrant right subclavian artery had a higher incidence in females (2 cases, 13.3%) than males (1 case, 6.7%) which is similar to Piyavisetpat et al. [16] and Karacan et al. [17].
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Sixty percent of cases showed the normal branching pattern of left sided aortic arch which agreed with Zhivadinovik et al. [18].
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Left-sided aortic arch with aberrant right subclavian artery came as the third common branching pattern detected by MDCT which agreed with Celikyay et al. [19]. It was the commonest anomalous form of left-sided aortic arch detected in our study which was the same result found by Raimundo et al. [20].
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Left-sided aortic arch with bovine branching pattern came as the fourth common detected aortic arch branching pattern with a percentage of 6% of cases which was close to the percentage detected by Müller et al. [21]. It was lower than the percentage detected by Jakanani et al. [22] which was 20% of their cases.
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One case of aortic coarctation was associated with left-sided aortic arch with bovine branching pattern. The presence of this anomaly with aortic coarctation cases required the use of median sternotomy instead of lateral thoracotomy during surgical repair, which was an added preoperative planning value for MDCT.
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Left-sided aortic arch with aberrant right subclavian artery (ARSA) and right-sided arch with mirror image branching pattern were associated with cases of tetralogy of Fallot (TOF), TGA, and truncus arteriosus which agreed with Tawfik et al. [23] and Turkvatan et al. [9].
The coronary artery anatomy is important for surgical planning of complete TGA. Surgical correction of TOF requires right ventriculotomy to relieve right ventricular outflow tract (RVOT) obstruction. Hence, any major coronary artery crossing the RVOT can be accidentally damaged during surgical repair [24].
In this study, cases with TGA and truncus arteriosus had higher prevalence of coronary anomalies compared to other cases of aortic anomalies which agreed with Yu et al. [24].
This study showed that MDCT has a high diagnostic sensitivity of thoracic aortic anomalies reaching up to 100% in different variables, with the advantage of giving precise anatomical details and volume rendered images which are very helpful before surgery for accurate surgery planning.
Both Echo and MDCT had 100% sensitivity in detection of aortic root anomalies. MDCT showed higher sensitivity in detection of aortic arch and descending aortic anomalies (MDCT 100%, Echo 91.4%). Echo was a better diagnostic tool in evaluation of aortic valve anatomy as motion artifact was a drawback in three cases that could not be evaluated by MDCT.
We acknowledge that the only limitation was the retrospective ECG gating thus relatively increase the radiation dose in infants and children.