Complementary role of computed tomography angiography with fixed perfusion defects on SPECT myocardial perfusion imaging

Abstract

Purpose
We present this case series exploring the complementary role of coronary computed tomography angiography (CCTA) to SPECT myocardial perfusion imaging (MPI) in the detection of myocardial necrosis.

Methods
A cardiac hybrid imaging database search identified 144 patients with a previous history of ST-segment elevation myocardial infarction treated with coronary revascularization. CCTA and MPI scans were evaluated to determine whether CCTA had an added value to MPI in detecting myocardial necrosis.

Results
Five patients with patent stents and/or bypass grafts and both fixed perfusion defects on MPI and sub-endocardial hypo-perfusion on CCTA were identified. The extent and location of the perfusion defects were closely correlated between the CCTA and SPECT MPI images.

Conclusion
In this series, CCTA and SPECT MPI were found to play a complementary role in the assessment of fixed perfusion defect, with CCTA adding specificity to the diagnosis of myocardial necrosis.

Full text

Complementary role ofcomputed
tomography angiography withxed perfusion
defects onSPECT myocardial perfusion imaging
Rami M. Abazid1* , Yasmine T. Sallam2, Jonathan G. Romsa1, James C. Warrington1, Cigdem Akincioglu1,
Sabe De3, Nikolaos Tzemos3 and William C. Vezina1
Introduction
Fixed perfusion defect (FPD) is a perfusion abnormality that is detected on both rest and
stress SPECT MPI scans of the identical location, size and severity (Garcia etal. 2020;
Busch etal. 2011). e presence of FPD is suggestive nonviable myocardial tissue. How-
ever, other causes for FPD include hibernating/viable myocardium and attenuation arti-
facts. e differentiation between infarct/scar and viable myocardium can be made with
Tl-201 single-photon emission computed tomography (SPECT) as well as Fluorodeox-
yglucose-positron emission tomography (FDG-PET). Late gadolinium enhancement
with cardiac magnetic resonance imaging is a specific finding of myocardial scar. On
the other hand, the presence of contractile reserve with dobutamine echocardiography
is regarded as a specific echocardiographic sign of a viable myocardium (Garcia etal.
2020). To date, few studies evaluated the diagnostic accuracy of first-pass CT myocardial
Abstract
Purpose: We present this case series exploring the complementary role of coronary
computed tomography angiography (CCTA) to SPECT myocardial perfusion imaging
(MPI) in the detection of myocardial necrosis.
Methods: A cardiac hybrid imaging database search identified 144 patients with a
previous history of ST-segment elevation myocardial infarction treated with coronary
revascularization. CCTA and MPI scans were evaluated to determine whether CCTA had
an added value to MPI in detecting myocardial necrosis.
Results: Five patients with patent stents and/or bypass grafts and both fixed perfu-
sion defects on MPI and sub-endocardial hypo-perfusion on CCTA were identified. The
extent and location of the perfusion defects were closely correlated between the CCTA
and SPECT MPI images.
Conclusion: In this series, CCTA and SPECT MPI were found to play a complementary
role in the assessment of fixed perfusion defect, with CCTA adding specificity to the
diagnosis of myocardial necrosis.
Keywords: Perfusion defects, SPECT, Coronary CT angiography
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CASE REPORT
Abazidetal.
European Journal of Hybrid Imaging (2022) 6:3
https://doi.org/10.1186/s41824-021-00124-z
European Journal of
Hybrid Imaging
*Correspondence:
ramiabazid@yahoo.com
1 Division of Nuclear
Medicine, Section of Cardiac
Hybrid Imaging, Victoria
Hospital, London Health
Sciences Centre, 800
Commissioners Road East, PO
Box 5010, London, ON N6A
5W9, Canada
Full list of author information
is available at the end of the
article
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Abazidetal. European Journal of Hybrid Imaging (2022) 6:3
perfusion with late-phase CT imaging (delay enhancement) in the detection of myocar-
dial scar. Additionally, no definite criteria exist to identify non-viable myocardium with
coronary computed tomography angiography (CCTA) without using the delay enhance-
ment scan (Garcia etal. 2020; Busch etal. 2011).
e purpose of this analysis is to explore whether CCTA has added value to SPECT
MPI in diagnosing nonviable myocardium.
Materials andmethods
We screened 2364 patients with atypical chest pain who were referred for combined
cardiac hybrid anatomic and functional imaging (CCTA and 2-day Rest/Stress SPECT
myocardial perfusion imaging (MPI)) in the period between January 2014 and January
2018. All registry patients signed consents to be imaged into a registry to be imaged with
CCTA and rest/stress SPECT-MPI and agreed to subsequent follow-up. is registry
was approved by the local ethical committee.
A two-day rest/stress protocol with Tc99m Sestamibi was employed for all patients.
SPECT MPI imaging was performed on a cadmium–zinc–telluride solid-state detector
(CZT) gamma camera with CT attenuation correction. e rest SPECT-MPI study and
the CCTA scan were done on the same day. e stress SPECT MPI scan was performed
the following day. Physically capable patients were stressed on the treadmill, while phar-
macologic stress with dipyridamole ± exercise was performed in patients with limited
exercise capacity.
CCTA was performed after oral pre-medication with a goal of reducing the heart rate
to less than 60 beats per minute. A 64-slice CT scanner was used for the CCTA within a
few hours of the rest-SPECT scan. A timing bolus technique was employed to determine
the delay time used to trigger the CCTA acquisition. Late-enhancement CT imaging was
not performed as part of this protocol.
A subgroup of patients (N = 144) with a history of ST-segment elevation myocar-
dial infarction (STEMI) who underwent revascularization with either percutaneous
coronary intervention (PCI) or coronary artery bypass surgery were reviewed. From
that subgroup, we report five patients with both FPD on SPECT-MPI scans and hypo-
enhancement on CCTA scans, Figs.1, 2, 3, 4 and 5. All 5 patients had patents stents/gra
fts.
Case series
Case‑1
A 66-year-old male with history of inferior STEMI treated with PCI to the right coro-
nary artery. Echocardiography showed LVEF of 60% with no regional wall motion abnor-
malities. Six years later MPI (Fig.1A, B) shows a small fixed defect (< 25% of the wall
thickness) at the mid infero-lateral wall segment (yellow arrows) suggestive of attenua-
tion artifact vs a perfusion defect. CCTA images (Fig.1C–E) show a patent stent (S) with
no obstructive lesions and localized mid infero-lateral sub-endocardial hypo-perfusion
(white arrows) supporting the MPI finding of a true FPD (myocardial necrosis rather
than attenuation artifact).
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Abazidetal. European Journal of Hybrid Imaging (2022) 6:3
Case‑2
A 78-year-old female with history of anterior STEMI treated with PCI to the left
anterior descending artery (LAD). Echocardiography showed LVEF of 50% with mild
hypo-kinesis of the anterior wall. Two years later MPI (Fig.2A, B) shows a large fixed
defect in the anterior wall (yellow arrows) with small area of a peri-infarct ischemia.
CCTA (Fig. 2C–F) shows a widely patent stent, mid LAD muscular bridge (red
arrows) and diffuse sub-endocardial hypo-perfusion (white arrows) at the anterior
and antero-septal wall involving < 50% of the wall thickness. ese segments appear
thinner than the posterior wall and the basal anterior wall. CCTA supports MPI find-
ing of a fixed defect likely due to endocardial scar after coronary revascularization
secondary to STEMI.
Case‑3
A 67-year-old male with history of anterior STEMI treated with PCI to LAD. Echo-
cardiography showed LVEF of 30% with akinetic anterior, anterior-septum and api-
cal segments. Four years later MPI (Fig.3A, B), shows large severe fixed defect in
mid and apical anterior, apex and the adjacent apical segments of the lateral and
inferior wall (yellow arrows). CCTA (Fig.3C–E) shows patent proximal stent (S1)
with no focal obstructions, the distal stent (S2) cannot be assessed. Beyond the distal
Fig. 1 A SPECT images, B polar maps at stress (upper panel) and rest (lower panel), C–E computed
tomographic angiography images. LV, left ventricle; LA, left atrium
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Abazidetal. European Journal of Hybrid Imaging (2022) 6:3
stent there is small LAD aneurysm (A). CCTA also shows a diffuse sub-endocardial
hypo-perfusion (white arrows) at the anterior wall and apex involving > 75% of the
wall thickness, apical LV aneurysm, thinned out anterior wall and apex and apical LV
thrombus (green arrows) with focal calcification.
Case‑4
A 75-year-old male with history of anterior STEMI at age 46years which was treated
with medical therapy. Fifteen years later he underwent hybrid coronary revascu-
larization [robotic-assisted minimally invasive coronary artery bypass surgery of
the left internal thoracic artery (LITA) to the LAD, and PCI to RCA]. Echocardiog-
raphy showed LVEF of 42% with hypo-kinesis of the anterior-septum, apical ante-
rior wall segments and the apex. MPI (Fig.4A, B), shows a large-sized, moderate to
severe fixed defect in the mid and apical anterior, anterior-septum and apex (yel-
low arrows). CCTA (Fig.4C–E) shows patent LITA graft and diffuse sub-endocardial
hypo-perfusion of approximately 50%-75% of the wall thickness (white arrows) at
the anterior, anterior-septal segments, and a thinned-out apex. The proximal RCA
stent (S) has no focal obstructions. CCTA also shows a pericardial calcification at
the lateral aspect of the heart (red arrows).
Fig. 2 A SPECT images, B polar maps at stress (upper panel) and rest (lower panel), C–F computed
tomographic angiography images. LV, left ventricle; LA, left atrium; BA, basal anterior wall; IW, inferior wall
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Abazidetal. European Journal of Hybrid Imaging (2022) 6:3
Case‑5
A 62-year-old male with history of anterior STEMI treated with PCI to LAD. Echocar-
diography showed LVEF of 48% with septal hypo-kinesis. MPI (Fig.5A, B), shows large-
sized moderate fixed defect in the anterior-septum, apical anterior wall and apex (yellow
arrows). CCTA (Fig.5C–E) shows patent stent (S) with no focal obstructions and diffuse
sub-endocardial hypo-perfusion of 50–75% of the wall thickness (white arrows) at the
septum and part of the anterior. ese segments appear thinner than the posterior wall
and the basal anterior wall.
Discussion
Myocardial necrosis can be identified with different imaging modalities. It appears as
FPD with cardiac SPECT and PET MPI imaging. Dobutamine stress echocardiography
has a specificity of 76% and sensitivity of 81% for the detection of viable myocardium
and the contractile reserve (Garcia etal. 2020). With cardiac magnetic resonance imag-
ing, the presence of sub-endocardial late gadolinium enhancement has a sensitivity of
95% in diagnosing non-viable myocardium (Garcia etal. 2020).
Myocardial necrosis can also be detected with CCTA as a sub-endocardial hypo-
enhancement. ere are few reports to have investigated the diagnostic accuracy of
Fig. 3 A SPECT images, B polar maps at stress (upper panel) and rest (lower panel), C–E computed
tomographic angiography images. LV, left ventricle; LA, left atrium
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Abazidetal. European Journal of Hybrid Imaging (2022) 6:3
hypo-enhancement on dynamic CT perfusion in the diagnosis of myocardial infarction
(Busch etal. 2011).
An FPD on SPECT-MPI can result in a diagnostic dilemma as to whether the defect
represents hibernating myocardium/repetitive stunning or scar, possibly necessitating
additional viability imaging (Dilsizian 2021) or less likely an attenuation artifact. Moreo-
ver, when an FPD accompanies a reversible defect, anatomical information with invasive
coronary angiography might be required.
In this study, patients were selected with revascularization and patent stent/graft on
CCTA to support the presumption that the SPECT findings represent a true FPD related
to myocardial necrosis, and not hibernating myocardium. In general, CCTA is not rec-
ommended in the analysis of stents due to limited diagnostic accuracy, particularly with
small stent diameters. However, when CCTA is combined with SPECT MPI in a hybrid
cardiac imaging session, many of these limitations can be overcome. CCTA also has
non-negligible radiation exposure in real-world practice (Andreini etal. 2020; Hossain
etal. 2020). However, newer CT generations enable single heartbeat acquisition and can
result extremely low radiation exposure (Kosmala etal. 2019). CZT SPECT is a flexible
technology which can dramatically decrease radiation dose by 60%-70% compare to con-
ventional cameras. us in the appropriate setting, the radiation dose for hybrid CCTA/
MPI studies using CZT cameras is similar to, or less than MPI alone using conventional
cameras (Henzlova and Duvall 2020; Schaap etal. 2013).
Fig. 4 ASPECT images, B polar maps at stress (upper panel) and rest (lower panel), C–E computed
tomographic angiography images. LAD, left anterior descending artery; LITA, left anterior thoracic artery; LV,
left ventricle; S, stent
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Abazidetal. European Journal of Hybrid Imaging (2022) 6:3
When indicated, CCTA with rest/stress SPECT can be complementary in the evalu-
ation of patients with prior history of STEMI and revascularization through the detec-
tion of myocardial/subendocardial scar, assessment of coronary stents (directly with
CCTA or indirectly with SPECT MPI) and non-stented coronary artery segments.
In this report, we illustrate that CCTA is a unique imaging modality, providing
both anatomical and perfusion details in patients with previous revascularization. In
this dataset of patients with a history of STEMI and patent stents and grafts, FPD on
SPECT MPI and subendocardial hypoperfusion on CCTA were found to be largely
congruent. e CCTA findings increased the specificity of the SPECT MPI find-
ings for myocardial necrosis as opposed to attenuation artifact or hibernating/viable
myocardium. e utilization of a combined hybrid cardiac assessment allowed for a
more definitive and comprehensive cardiac assessment. However, our findings can-
not be generalized to patients with FPDs and severe coronary artery stenosis, as the
hypo-enhancement with CCTA might result from resting ischemia and hibernation.
Although promising, further studies enrolling patients without previous revascu-
larization and comparing hypo-enhancement with CCTA with other cardiac viability
imaging modalities such as cardiac MRI and FDG-PET are warranted.
Fig. 5 A SPECT images, B polar maps at stress (upper panel) and rest (lower panel), C–E computed
tomographic angiography images. LV, left ventricle; S, stent
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Abazidetal. European Journal of Hybrid Imaging (2022) 6:3
Abbreviations
CCTA : Coronary computed tomography angiography; LAD: Left anterior descending artery; LVEF: Left ventricle ejection frac-
tion; MPI: Myocardial perfusion imaging; PCI: Percutaneous coronary intervention; STEMI: ST-segment elevation myocardial
infarction.
Acknowledgements
None.
Authors’ contributions
RMA, advised the idea of the study and collected the data with Dr YTS. Dr JGR, Dr JCW, and Dr CA reviewed SPECT images. Dr
SD, Dr WCV and Dr NT reviewed the CTA images. All authors contributed to the discussion and the writing of the manuscript.
All authors read and approved the final manuscript.
Funding
No specific funding was available to support this study.
Availability of data and materials
Data sharing is not applicable to this article as the data of the present study are being used in other ongoing study which
have not been completed.
Declarations
Ethics approval and consent to participate
All procedures performed in studies involving human participants were in accordance with the ethical standards of the
institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or compa-
rable ethical standards.
Informed consent
Informed consent was obtained from all individual participants included in the study.
Competing interests
The authors declare that they have no competing interests.
Author details
1 Division of Nuclear Medicine, Section of Cardiac Hybrid Imaging, Victoria Hospital, London Health Sciences Centre, 800
Commissioners Road East, PO Box 5010, London, ON N6A 5W9, Canada. 2 Division of Medical Imaging, Northern Ontario
School of Medicine, Sudbury, ON, Canada. 3 Division of Cardiology, Department of Medicine, London Health Sciences
Centre, London, ON, Canada.
Received: 27 October 2021 Accepted: 27 December 2021
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