ReviewCardiac CT angiography in children with congenital heart disease
Introduction
Congenital heart disease (CHD) remains a major cardiac problem in the pediatric population. Cardiac imaging plays an important role in establish the diagnosis, interventional management, follow-up after palliative or corrective surgery. Various imaging modalities for the diagnosis of CHD progress from plain chest radiograph, 2-dimensional echocardiography and conventional cardiac catheterization to non-invasive advanced cardiac imaging, 3- and 4-dimensional echocardiography, transesophageal echocardiography, cardiac MRI (cMRI), and multidetector CT (MDCT). Echocardiography remains a first-line non-invasive imaging tool for establishing the diagnosis and follow-up in most patients. However, echocardiography has inherent limitations, including a limited acoustic window. This is particularly the case with post-surgical sternal wires and mediastinal scar tissue, and extracardiac vascular structures. Echocardiography is also an operator-dependent imaging tool with poorer spatial resolution than CT or CT angiography CT(A) [1], [2]. Cardiac catheterization, the gold standard for cardiac imaging with hemodynamic assessment, is an invasive method which may cause death in up to 1% of neonates with complex CHD [2], [3]. Its role has largely been replaced by other advanced non-invasive imaging tools. Currently, cardiac catheterization is reserved for hemodynamic assessment, in cases with pulmonary hypertension and complex CHD in whom the data regarding pulmonary vascular resistance, oxygen saturation and chamber pressure are essential for surgical planning, and in whom interventional treatment is necessary [1]. Cardiac CT(A) (cCTA) is a non-invasive tool, with high image spatial resolution, and powerful 3-dimensional post-processing image reconstruction. This provides excellent anatomic information that can replace echocardiography and cardiac catheterization, particularly in the evaluation of extracardiac vessels and coronary arteries [4], [5], [6]. However, cCT(A) had poorer temporal resolution relative to other cardiac imaging modalities such as echocardiography, cardiac catheterization and cMRI [1]. A comparison of cardiac imaging modalities, echocardiography, cardiac catheterization, and cCT(A) is presented in Table 1.
This review article will focus on the fundamentals and essentials for performing cCT(A) in children, including radiation dose awareness, basic CT(A) techniques, applications, and strengths and weaknesses of cCT(A) comparing with cMRI. We also discuss the limitations of this modality for evaluation of some CHD where cMRI could be a reasonable substitution.
Section snippets
MDCT scanner requirements for evaluating children with congenital heart disease
A 64-slice MDCT is the minimum solution recommended for evaluating CHD and coronary artery disease in children because of reduction of the radiation dose and improvement of image quality by using noise reduction algorithms. With the development of fast gantry rotation speed and wider collimation coverage in 64-slice MDCT, the scan duration is reduced, temporal resolution is increased, and hence motion artifacts are decreased [4]. The newer generation MDCT scanners, 256 to 320/640-slice MDCT and
Sedations and patients’ preparations
Sedation prior to scanning prevents agitation during contrast delivery to children, avoiding the need for repeated examinations with increasing the radiation burden. In our experience with a 320-slice and a 64-slice MDCT, sedation is not necessary in neonates, calm babies, and children older than six years of age. In our institution, the sedation protocol includes intravenous Midazolam diluted at a dose of 0.1 mg/kg/dose prior to the scan. Additional sedative drugs such as a diluted Fentanyl at
Contrast medium injection and venous assessment
Non-ionic, low- or iso-osmolar iodinated contrast agents are preferable because they are safer [10]. Impaired renal function is an absolute contraindication for iodinated contrast medium (CM) administration. The risk of contrast-induced nephrotoxicity is increased in neonates due to the immaturity of renal function [5], so the volume of CM should be kept as small as possible but should be enough to maintain interpretable image quality, particularly considering the relatively higher circulating
Radiation awareness
The most important consideration regarding cCT(A) in children with CHD is how to keep the radiation dose as low as reasonably achievable (ALARA) with the balance of interpretable image quality which partly depends on individual radiologist preference and experience – but eventually needs to be diagnostic, not the optimum. Image quality is determined by spatial and contrast resolutions and image noise. The spatial resolution depends on the detector width or beam collimation while the contrast
Cardiac CT(A) techniques
The cCT(A) comprises two acquisition modes, non-ECG gated and ECG-gated acquisitions. Since echocardiography is an excellent tool for delineation of the intracardiac anatomy and pathology, non-ECG gated acquisition is therefore mainly used for evaluation of extracardiac structures while the ECG-gated acquisition is used primarily for coronary artery imaging. Non-ECG gated acquisition of the heart should be acquired with an attempt to reduce motion and pulsatile artifacts by choosing the highest
Reading cardiac CT(A)
The basic segmental approach described by Van Praagh is fundamental for interpretation of the anatomy of children with complex CHD [22]. The approach consists of three anatomical descriptions (the viscero-atrial situs, the ventricles, and the great vessels morphology) and two connections (atrioventricular and ventriculoarterial). The pulmonary veins, systemic veins, and associated other cardiac anomalies should be carefully evaluated. There are limitations in evaluation of the valves apparatus
Cardiac CT(A) compared to cardiac MRI
While both cCT(A) and cMRI give excellent spatial resolution, cCT(A) has higher spatial resolution while cMRI has a better temporal resolution [2], [23]. Cardiac CT(A) is a rapid scanning tool with powerful 3-dimensional post-processing image reconstruction options. It is a more applicable imaging tool for critically ill children and in the emergency setting – compared with cMRI which has a more complex setting and long scanning time [5], [11], [24]. Although, radiation exposure and CM risks
Pulmonary arteries and systemic-blood-supply to the lungs
The anatomical detail of the pulmonary artery (PA) and its branches is important in Tetralogy of Fallot (TOF), because there is either central or peripheral pulmonary artery stenosis in about 10% of the patients [11], [25]. Pulmonary atresia is also a common CHD referred for evaluation of the PA and systemic-blood-supply to the lungs [11]. CT pulmonary angiogram (CTPA) is useful for PA assessment because the echocardiography can be limited in evaluation of the branch pulmonary arteries, and
Cardiac MRI as an alternative tool to cardiac CT(A)
Both cCT(A) and cMRI have their strengths and weaknesses, thus the choice and selection of the modality depends primarily on the clinical questions (Table 6). In general, the indications for both modalities can be grouped into intra-cardiac and extra-cardiac morphologies. Intra-cardiac pathology is usually best determined by echocardiography, only a few conditions require for additional studies. Evaluation of extra-cardiac vessels is the most common indication for cCT(A) and MRI [24]. All
Conclusion
Cardiac CT(A) is a very rapid imaging procedure giving excellent spatial resolution. Post-processed three-dimensional images facilitate the understanding of the complex anatomy. The strengths of cCT(A) complement the weaknesses of cMRI, particularly in patients in whom cMRI is contraindicated. Cardiac CT(A) is an important non-invasive diagnostic tool for evaluating CHD, particularly extra-cardiac vessels and coronary arteries. Cardiac CT(A) is not the modality of choice for evaluation of
Conflict of interest
None.
Acknowledgements
The authors would like to thank Professor Michael Riccabona, MD for his critical proofreading and editing of the manuscript and suggestions for this review article.
References (47)
- et al.
Introduction to cardiac imaging in infants and children: techniques, potential, and role in the imaging work-up of various cardiac malformations and other pediatric heart conditions
Eur J Radiol
(2008) - et al.
Cardiac catheterization of low-birth-weight infants
Am J Cardiol
(2001) - et al.
Pediatric computed tomographic angiography: imaging the cardiovascular system gently
Radiol Clin N Am
(2010) - et al.
Dose reduction in paediatric MDCT: general principles
Clin Radiol
(2007) - et al.
Safety and accuracy of 64-slice computed tomography coronary angiography in children after the arterial switch operation for transposition of the great arteries
JACC Cardiovasc Imaging
(2008) - et al.
Tips to minimize radiation exposure
J Cardiovasc Comput Tomogr
(2008) MR and CT imaging of the pediatric patient with structural heart disease
Semin Thorac Cardiovasc Surg Pediatr Card Surg Annu
(2009)- et al.
Regression of aneurysms in Kawasaki disease: a pathological study
J Pediatr
(1982) - et al.
Patent levoatrial cardinal vein without left heart hypoplasia
Ann Thorac Surg
(2006) - et al.
The Ross procedure in infants and young children
Ann Thorac Surg
(2008)
Repair of pulmonary arterial stenosis after Waterston–Cooley anastomosis
J Thorac Cardiovasc Surg
Tetralogy of Fallot
Lancet
Magnetic resonance measurement of velocity and flow: technique, validation, and cardiovascular applications
Am Heart J
Neonatal cardiac multidetector row CT: why and how we do it
Pediatr Radiol
Neonatal cardiac imaging
Pediatr Radiol
CT in the evaluation of congenital heart disease in children, adolescents, and young adults
Curr Treat Options Cardiovasc Med
Use of 320-detector computed tomographic angiography for infants and young children with congenital heart disease
Pediatr Cardiol
Multislice CT angiography in cardiac imaging: prospective ECG-gating or retrospective ECG-gating?
Biomed Imaging Interv J
Multidetector CT for congenital heart patients: what a paediatric radiologist should know
Pediatr Radiol
Multiplanar and three-dimensional multi-detector row CT of thoracic vessels and airways in the pediatric population
Radiology
Role of CT in the evaluation of congenital cardiovascular disease in children
Radiology
Low-kilovoltage multi-detector row chest CT in adults: feasibility and effect on image quality and iodine dose
Radiology
Dual-source CT in step-and-shoot mode: noninvasive coronary angiography with low radiation dose
Radiology
Cited by (47)
Utility of cardiac CT in infants with congenital heart disease: Diagnostic performance and impact on management
2022, Journal of Cardiovascular Computed TomographyCitation Excerpt :Several noninvasive imaging modalities are available, but echocardiography is the first-line technique in most infants.3,4 However, echocardiography can be limited by sonographic windows and evaluation can sometimes be incomplete or inadequate.5–7 Magnetic resonance imaging can help complete diagnostic evaluation when echocardiographic assessment is inadequate, but in infants, it may require general anesthesia, and image quality can be limited by small body size and rapid heart rate.4,8
Diagnostic value of scoring model of treadmill exercise test combined with dynamic electrocardiogram for latent coronary heart disease
2021, Journal of ElectrocardiologyRole of computed tomography in adult congenital heart disease: A review
2021, Journal of Medical Imaging and Radiation SciencesComparison of echocardiography and 320-row multidetector computed tomography for the diagnosis of congenital heart disease in children
2021, Revista Portuguesa de CardiologiaCitation Excerpt :This modality is noninvasive, with high spatial resolution and powerful three-dimensional (3D) post-processing image reconstruction. It thus provides excellent anatomic information that can replace echocardiography and cardiac catheterization, particularly in the assessment of extracardiac vessels and coronary arteries.3–5 Older CT scanners, using a retrospective electrocardiogram (ECG)-gated scan mode, have been reported to expose CHD patients to effective radiation doses of up to 28 mSv per cardiac scan.6
Cyanotic and acyanotic congenital heart disease
2021, Pediatric Imaging for the Emergency Provider