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Relatively recent advances in pediatric cardiovascular surgery, catheter-based
interventional therapies, intensive care, and medical management
have dramatically changed the landscape of the field of congenital
heart disease (CHD). The complexity of the anatomy and physiology
of patients surviving with CHD increases exponentially. The majority
will survive to adulthood, and the need for reintervention is common.
As such, the field is placing new demands on imaging to diagnose
and plan medical management, as well as to identify need for and
timing of reintervention. There are a number of imaging modalities
available to the clinician and radiologist when it comes to these
evaluations.
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Echocardiography (ECG) has been and remains a mainstay of imaging
in congenital heart disease. Despite its importance in rapid diagnosis
and follow-up, it has limitations. The presence of postoperative
scar, chest wall deformities, overlying lung tissue, and large body
size as the patient ages often results in suboptimal transthoracic
echocardiographic windows. Transesophageal echocardiography provides
improved acoustic windows, but is limited by its small field of
view and more invasive nature.
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Cardiac catheterization, employing x-ray fluoroscopy and contrast
angiography, has an expanding role in minimally invasive interventions,
but its role as a diagnostic procedure is rapidly diminishing. This
is in part due to its limitation as a 2-dimensional projection imaging
technique with poor soft tissue contrast and the substantial ionizing
radiation exposure involved and in part because both diagnostic
and functional analyses are often better performed with noninvasive
imaging techniques.
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This chapter focuses on the evolving and expanding roles of other
imaging modalities in diagnosing and monitoring patients with congenital
heart disease, including cardiac magnetic resonance imaging (MRI),
cardiac computed tomography (CT), and radionucleotide scintigraphy.
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Cardiac magnetic resonance imaging (MRI) has emerged over the
past few decades as an alternative, complementary, and frequently
superior imaging modality for investigating the anatomy and function
in the patient with congenital heart disease. It has many advantages over
other imaging modalities. It does not require the use of iodinated
contrast agents and does not involve exposure to ionizing radiation. This
is particularly important in a population of patients who have been,
and continue to be, exposed to large doses of contrast agent and
radiation during hemodynamic and interventional catheterization.
Additionally, many of these patients are children who are more susceptible
to the adverse effects of radiation. Major advances in MRI hardware
and software, including advanced coil design, faster gradients,
new pulse sequences, and faster image reconstruction techniques,
allow rapid, high-resolution imaging of complex anatomy and accurate,
quantitative assessment of physiology and function.
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Cardiac MRI Techniques
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There are a number of MRI techniques useful in examining the anatomy
and physiology of the congenital heart disease patient.
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ECG-gated gradient-echo sequences provide multiple images throughout
the cardiac cycle in prescribed anatomic locations. Display of these
images in a cine mode allows visualization of the dynamic motion ...