Aside from radiation, other unique considerations, both risks and benefits, are involved in performing cardiac CTs on pediatric patients. A major benefit of the increased temporal resolution of cardiac CT is that the need for sedation is minimized. Children over the age of 3 years can usually remain still for the brief time needed for CT acquisition. Breath-holding may not be required for volumetric or high-pitch scanners, though it is still needed for imaging acquired over several heartbeats or coronary artery imaging [39, 43]. At our institution, for 3D printing purposes, we typically administer at least moderate sedation to patients under 3 years to avoid blurring from motion and minimize stair-step artifact on our step-and-shoot CT scanner. In neonates, in whom anatomic structures are small and spatial resolution is important, we will consider intubation, paralysis, and suspending ventilation to acquire very high-quality datasets for prototyping. Often, neonates facing the prospect of complex surgical repair requiring 3D modeling are critically ill and may be already intubated in the neonatal intensive care unit.

As previously mentioned, cardiac CT does not require the use of gadolinium, but does require intravenous injection of iodinated contrast at doses of about 1–2 mL/kg. Though not associated with neurotoxicity, CT contrast can induce nephropathy in patients with decreased renal function. This is often a concern in children with CHD and pediatric patients who have undergone a heart transplant. Patients may benefit from pre-hydration and treatment with protective agents like n-acetyl cysteine [44, 45]. Contrast extravasations are rare, even when using a power injector in a 24-gauge IV in a neonate [46]. Risk of iodinated contrast allergy is higher than that of gadolinium-based agents but is typically less than 0.5% in children [47, 48]. In patients with aortopulmonary shunts or a Fontan palliation, it is particularly important to tailor contrast injection protocols to a patient’s specific anatomy and circulation pathways. When imaging a patient after Fontan palliation, some groups suggest simultaneous contrast administration through upper and lower extremity intravenous lines to opacify the entire pathway, though delaying imaging after contrast injection may also achieve the same effect [49, 50].

Other benefits of cardiac CT include its ability to simultaneously image extracardiac structures such as the airway and lung parenchyma with high-spatial resolution. It is also ideal for patients with metallic devices such as pacemakers or stents that are either contraindicated in MRI or may cause significant artifact. CT is optimal for critically ill patients, who may not be stable enough to undergo long MRI examinations [37]. The relatively high heart rates of pediatric patients are not a significant limitation to obtaining high-quality CT images unless coronary imaging is a critical component of a 3D model. If coronary imaging is needed, beta blockers or calcium channel blockers may be administered when indicated in order to reduce the heart rate to less than 70, and ideally less than 60, beats per minute to achieve adequate image quality. Our group recently reported that using an intravenous phenylephrine infusion in conjunction with these medications can further decrease heart rates even in young children by supporting blood pressure as well as causing reflex bradycardia [51]. Such low heart rates may not be safely achievable in very young patients, however [39].