Emerging Role of Stress Perfusion
Cardiovascular Magnetic Resonance
in the Patient with Congenital Heart
Disease
Andrew M. Crean, Djeven P. Deva, and Rachel Wald
Contents Interpretation of Stress Perfusion CMR . . . . . . . . . . . 10
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Limitations of Stress Perfusion CMR . . . . . . . . . . . . . . 11
Limitations of Conventional Methods Treadmill Stress CMR: Perfusion and
of Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Wall Motion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
The Comprehensive Nature of the CMR Data from the Adult Ischemic Stress
Examination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 CMR World . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Limitations of CMR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Stress Perfusion CMR in Patients Following
Arterial Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Physical Preparation of the Stress Patient . . . . . . . . . 5
Stress Perfusion CMR for Anomalous Left/Right
Mental Preparation of the Stress Patient . . . . . . . . . . 6 Coronary Artery from the Pulmonary Artery
Choice of Vasodilator Agent . . . . . . . . . . . . . . . . . . . . . . . . 6 (ALCAPA/ARCAPA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Assessment of Vasodilator Effect on the Stress Perfusion CMR in Kawasaki Disease . . . . . . . 14
Patient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Stress Perfusion CMR in Assorted Other
Monitoring for Stress Perfusion CMR . . . . . . . . . . . . . 8 Congenital Lesions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Practical Aspects of Performing Stress Perfusion Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
CMR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
A.M. Crean (*)
Division of Cardiology, University of Cincinnati Medical
Center and Cincinnati Children’s Hospital Medical Center
and Joint Department of Medical Imaging, Toronto
General Hospital, Toronto, Canada
e-mail: andrewcrean@gmail.com
D.P. Deva
Department of Medical Imaging, St Michael’s Hospital,
Toronto, Canada
e-mail: devad@smh.ca
R. Wald
Division of Cardiology and the Joint Department of
Medical Imaging, Toronto General Hospital, Toronto,
Canada
e-mail: rachel.wald@uhn.ca
# Springer-Verlag London 2016 1
E.M. Da Cruz et al. (eds.), Pediatric and Congenital Cardiology, Cardiac Surgery and Intensive Care,
DOI 10.1007/978-1-4471-4999-6_250-1
,2 A.M. Crean et al.
Abstract fascinating coronary anomalies – the anomalous
Rapid advances in surgical repair of congenital left or right coronary artery from the pulmonary
heart disease has led to ever increasing num- artery, the anomalous left or right coronary artery
bers surviving into adult life. A proportion of from the opposite sinus, etc. – these patients are in
adult congenital heart disease (ACHD) patients fact outnumbered by those who have undergone
will have had direct surgical intervention upon coronary reimplantation procedures as part of a
the coronary arteries which renders them vul- Ross, Bentall, or Jatene arterial switch operation.
nerable to issues in later life. There is no This latter group represents a particularly interest-
accepted method for either the surveillance of ing challenge for management and surveillance
these patients nor for their investigation when for several reasons: this is not a rare operation at
presenting with new symptoms. This chapter any large congenital center; the patients need to be
argues for a shift in paradigm away from test- followed for many years; as children the typical
ing associated with radiation (nuclear tech- presentations of ischemic chest pain recognized in
niques, computed tomography, coronary the adult may be absent; and sudden cardiac death
angiography) to a paradigm where stress per- has been occasionally reported as an unfortunate
fusion cardiac magnetic resonance (CMR) first (and last) indicator of a previously
imaging is used as a gatekeeper to determine unsuspected coronary problem.
who needs go on for formal catheterization. There is a second large group of patients who
The technique of stress perfusion CMR is are typically also followed by pediatric cardiolo-
discussed along with its benefits and weak- gists (and then often graduate to adult congenital
nesses. Practical illustrations of the technique’s cardiologists), despite being born with structur-
utility are provided throughout the chapter. ally normal hearts – these are the children who
succumb to Kawasaki disease, a proportion of
whom will develop cardiac abnormalities as part
Keywords of the inadequately named mucocutaneous lymph
Anomalous left/right coronary artery from the node syndrome. The coronary aneurysms that
pulmonary artery (ALCAPA/ARCAPA) • result in some cases may have important effects
Arterial switch • Calcified conduits and calcific on distal coronary flow that pass unrecognized,
masses • Cardiovascular magnetic resonance particularly in children, and the natural history of
(CMR) • Congenital heart disease (CHD) • these aneurysms in adult life is not well
Coronary surveillance • Dark-rim artifact understood.
(DRA) • Dipyridamole • Ischemic stress Regular coronary surveillance is therefore
CMR • Kawasaki disease • Nitinol-based appropriate for several patient populations
devices • Perfusion imaging • Regadenoson • followed in congenital heart centers. The literature
Stress perfusion CMR • Treadmill stress • supplies advocates for almost any of the available
Vasodilator imaging modalities: computed tomography, echo,
nuclear, and catheterization, although there are
almost no large studies in this area. In this chapter,
Introduction we would like to present our experience that stress
perfusion cardiovascular magnetic resonance
The success story that has been the surgical man- (CMR) imaging is not only the most appropriate
agement of patients with congenital heart disease test for these children and young adults but is also
(CHD) over the last 50 years has brought its share – quite simply – the most complete of the imaging
of challenges due to the “unnatural history” fol- modalities. The following section will discuss in
lowing repair. Our patients are not only born with greater detail the comprehensive nature of CMR,
coronary anomalies but may have coronary abnor- while subsequent sections will deal with the prac-
malities created by the surgical procedures them- tical procedural elements of performing stress
selves. Although we tend to think of the rare and CMR, its applications in the patient groups
,Emerging Role of Stress Perfusion Cardiovascular Magnetic Resonance in the Patient with. . . 3
described, the evidence base for stress CMR in the change. For congenital patients who are unable to
adult ischemic world, and the (very) limited cur- exercise adequately, vasodilators such as adeno-
rent data on stress CMR for patients with congen- sine or dipyridamole may be used to induce coro-
ital heart disease. nary hyperemia (note not ischemia – a common
misconception regarding vasodilator stress).
Vasodilator stress is well tolerated and incred-
Limitations of Conventional Methods ibly safe with a very low major adverse cardiac
of Assessment event rate borne out by millions of pharmacologic
stress nuclear studies throughout the world. For
One of the unique challenges facing congenital reasons of availability, ease of performance, and
heart patients is the requirement for lifelong patient acceptability, nuclear stress perfusion has
follow-up. In patients with coronary “issues” or become widely accepted as one of several “first-
in whom coronary artery reimplantation has been choice” techniques in European and (particularly)
performed, this challenge is particularly relevant. North American congenital institutions. However,
As physicians we seek to limit radiation exposure physicians referring their patients for these studies
to our patients, and yet many of our conventional often have only a hazy idea at best of the dose
methods for assessing the coronary arteries associated with this test [5]. Many are surprised to
involve ionizing radiation. The use of ionizing learn that it is equivalent in dose to roughly 3–4
radiation in congenital populations was described coronary angiograms (technetium – rest/stress
in a recent European-wide registry, which dose approximately 15 mSv) or as high as 8 coro-
highlighted the potential for significant cumula- nary angiograms (thallium – rest/stress dose
tive lifetime doses in our patients [17]. approximately 40 mSv).
There has historically been a very heavy While all data linking exposure to subsequent
dependence upon cardiac catheterization in con- cancer is questionably based upon theoretical
genital heart disease. Not only is it available at assumptions derived from the Nagasaki and Hiro-
every major center, it provides unparalleled visu- shima events – as well as an unproven assumption
alization of the coronary arteries with a spatial of a linear no-threshold relationship between dose
resolution that is still not really approached by a and malignancy – physicians are nevertheless
modern method of noninvasive imaging. While appropriately seeking to shield their (young,
this is certainly necessary in the preoperative radiosensitive) patients from the excesses of the
period or if there are major coronary concerns, past. A further limitation of nuclear cardiology
catheterization is expensive, is disliked by some reflects the physical limitation of current equip-
patients, and comes with a small risk of serious ment. Post-collimator spatial resolution is in the
morbidity and death. It is thus not an ideal tech- order of 8–10 mm – since this is approximately
nique to use in routine follow-up for coronary the same as transmural myocardial thickness, it
surveillance, although even in this situation it can be difficult to recognize subendocardial ische-
has its advocates. mia or balanced three-vessel disease. This is a
Perfusion imaging with radionucleotide iso- point we will return to in subsequent discussion
topes (thallium, technetium, etc.) has been avail- about stress perfusion cardiovascular magnetic
able for many years, is easy to perform and readily resonance (CMR) imaging.
available, and is well tolerated by patients. The Treadmill stress echo has been historically
basis of perfusion imaging (nuclear and magnetic underused in congenital populations for reasons
resonance) is the induction of differential tracer that are not entirely clear but may reflect dominant
flow down the arteries which vasodilate normally adult experience in the ischemic world with much
versus those which are narrowed, distorted, or lower levels of experience/confidence in the tech-
obstructed. Stress may be performed by treadmill nique in pediatric institutions. However, even
exercise in which case there is also the advantage adult congenital institutions appear less enthused
of having workload data and assessment of ECG with this method of assessment compared to the
, 4 A.M. Crean et al.
alternatives of single-photon computed emission demonstrated by administering gadolinium-
tomography (SPECT) or CMR imaging. This is a based contrast agents (magnetic resonance angi-
pity because the need in coronary surveillance is ography) and myocardial scarring identified using
to rule out significant flow limitation – which is the technique of late gadolinium enhancement
something stress echo does particularly well. A (LGE) imaging in which images of the heart are
further advantage is the availability, again, of acquired 10–15 min after a bolus of contrast,
workload and ECG data. Finally, of course, there allowing for differential washout between normal
is no exposure to ionizing radiation at all with this and abnormal areas of the myocardium
technique, making it attractive for long-term fol- [8]. Through a process of cardiac gating to the
low-up. Patients unable to adequately raise their ECG, it is possible to acquire so-called “seg-
heart rate by exercise can be stressed by mented” cine images in which data acquired
dobutamine infusion with little or no change in over a number of heart beats is used to build up
the sensitivity and specificity of the test. One a composite beating image of the heart with an
limitation of the technique is the need for a rea- effective temporal resolution in the order of
sonable echo window, which may be difficult or 35 milliseconds. Similar techniques can be
limited in patients with chest wall deformity or employed to visualize flow in vascular structures
simple obesity. There is also a rather providing information (via a very different phys-
unquantifiable “impression” among many cardi- ical principle) similar to Doppler echocardiogra-
ologists that reading stress echo is a rather dark art phy [28]. Phase-contrast imaging of this sort
and somewhat subjective. While these authors allows for the relatively precise measurement of
would challenge that opinion, there is of course flow volumes as well as peak and mean velocity in
little or no data to support the argument either way the user-defined region of interest. Finally, user-
in the congenital field. defined imaging planes can be prescribed in any
It is fair to say that the whole area of imaging in orientation to acquire anatomically helpful images
congenital heart disease is riddled with opinions, aligned to the anatomy of interest without any
conjecture, and personal beliefs stated as gospel limitation by body shape or imaging “window.”
truth. Data are very limited even for well- Therefore – in a comprehensive CMR exam – it is
established techniques like SPECT, are almost possible to acquire valuable information about
nonexistent for stress echo, and are only just anatomy, function, flow, perfusion, and fibrosis
starting to emerge for stress CMR. In the rest of in a protocol that takes less than 60 min to perform
this chapter, the authors will share their bias in and without any ionizing radiation at all.
favor of stress CMR, explaining why we hold
these opinions and what little published evidence
exists. Limitations of CMR
Despite its many advantages, CMR has several
The Comprehensive Nature of the CMR important limitations. The magnet bore is claus-
Examination trophobic to a small percentage of individuals
with an examination refusal or non-completion
The principal advantage of CMR over all other rate of around 5 %. The newer magnets with a
forms of imaging is its comprehensive nature. 70 cm diameter bore compare favorably with the
Manipulation of the water protons intrinsic to the standard 60 cm bore present in most 1.5 T sys-
patient by use of strong switching magnetic fields tems, although the latter remain much more prev-
results in the ability to characterize tissue with alent. Some patients who appear initially reluctant
much greater contrast resolution than any other to enter the magnet can be reassured by a combi-
technique. Various “weightings” can be applied, nation of either medication or eye shield. Pediatric
designed to enhance the visibility of edema, fibro- institutions sometimes have third-party equip-
sis, thrombus, etc. Vascular structures can be ment that makes it possible to show videos inside
