Download Diagnosis of Anomalous Coronary Arteries in 64-MDCT

中華放射醫誌 Chin J Radiol 2007; 32: 111-119
111
Diagnosis of Anomalous Coronary Arteries in
64-MDCT
K u ei -Yua n H ou1 C hi n -M i ng J eng1,2 Ya p -P i ng L i u1 Tzu -H usa n Wa ng1 Tiem -M i ng L i n1
S hi -Wen C hen1 C hi -J en C hen1 Yua n -H eng M o1,2,3
Department of Radiology1, Cathay General Hospital
College of Medicine2, Fu Jen Catholic University
Institute of Biomedical Engineering, College of Engineering and College of Medicine3, National Taiwan University
Anomalous coronary arteries can be benign or
life threatening. Novel advances on multi-detector
computed tomography (MDCT) provide a noninvasive technique and offer an accurate diagnostic
modality to visualize the origin and course of
anomalous coronary arteries by a 3D display of
anatomy. Thus we demonstrated anomalies of coronary arteries shown by 64-MDCT in our institution.
540 subjects referred to our Hospital for MDCT
coronary angiography were included in this study.
These subjects were between the ages of 12 and 90
years (mean 59±12.6 years) including 297 (55%)
male and 243 (45%) female. Post-processing techniques such as volume rendering (VR) and maximum intensity projection (MIP) were applied to
demonstrate the coronary artery anatomy. Both a
radiologist and a cardiologist evaluated all examinations.
The incidence of anomalous anatomical origin
and course of the coronary arteries in our study
group was 15% (n = 81). The anomalies found in
our study are absence of left main coronary artery
(n = 3, 0.5%), high take-off origin of left main coronary artery (n= 1, 0.2%), ectopic origin of right
coronary artery from the left coronary sinus (n =
8, 1.5%), and myocardial bridging (n = 68, 12.6%).
Reprint requests to: Dr. Yuan-Heng Mo
Department of Radiology, Cathay General Hospital.
No. 280, Sec. 4, Jen Ai Road, Taipei 106, Taiwan, R.O.C.
MDCT with VR and MIP techniques is practical
for assessment of anomalous coronary arteries and
helpful for radiologist, cardiologist and surgeon.
Anomalous coronary arteries can be benign or
life threatening [1, 2]. Anomalous coronary arteries
are usually incidental findings during conventional
coronar y angiography [3, 4, 5]. Identif ication of
anomalous coronary anatomy is important for cardiologist and surgeon because of difficulty during
catheterization, operation of great vessels and its
rare complications such as myocardial ischemia and
sudden cardiac death [2]. Novel advances on multidetector computed tomography (MDCT) provide a
noninvasive technique and offer an accurate diagnostic modality to visualize the origin and course
of anomalous coronary arteries by a 3D display of
anatomy [2, 4, 5, 6, 7, 8, 9]. In this article, we aimed
to demonstrate remarkable anomalies of coronary
arteries shown by 64-multidetector computed tomography (64 -MDCT) coronar y angiography in our
institution.
MATERIALS AND METHODS
Subjects
Five hundred and forty subjects referred to our
Hospital from Jun. 2006 to Jun. 2007 were recruited
in this study. The subjects were between the ages
of 12 and 90 (mean 59±12.6 years), including 297
(55%) male and 243 (45%) female; 432 for health
examination, 105 for coronary syntoms, and 3 under
18 years old with past history of Kawasaki disease.
When performing the practice in young persons,
we adjusted kV(100-120), mA (250-350) and pitch
(0.3-0.4) to decrease the radiation dose. We had no
attempt to perform MDCT angiography for patients
with history of sustained arrhythmia (such as atrial
f ibrillation, vent ricular premat ure cont raction),
112
Diagnosis of anomalous coronary arteries
known allergic reaction to contrast media, deteriorated renal function (serum creatinine, >1.6 mg/dl),
pregnancy, respiratory insufficiency, poor clinical
condition, bronchial asthma and atrioventricular conduction block in which use of β-blocker was contraindicated, and those unable to hold their breath up to
10 seconds .
Pre-medication
Patients were all in sinus rhythm and received
oral β-blocker (10-40 mg of oral Propranolol administered 0.5 hour before the scan) except for those
with a heart rate below 65 beats per minute. For
those who received β-blockers, when their heart rate
below 70 beats per minute we started the examinations. Those who had poor control of heart rate
(over 70) were excluded in this study. The dosage of
β-blockers applied to the subjects was from 10mg
to 40 mg and it was depended on the subjects' heart
rate.
Scan Protocol
MDCT was performed in a 64-MDCT scanner
(Brilliance; Philips Medical Systems, Cleveland,
OH) during one breath hold period (8-10 seconds).
The parameters of our scanning protocol were: 64
× 0.625-m m colli mat ion, 120 -140 kV, 40 0 - 60 0
mA, 0.42 second rotation time, a pitch value of 0.2,
0.8-mm slice thickness, and 0.6-mm reconstr uct ion i nter val. Bolus-t rack i ng method was used
and the scanning field included entire heart from
proximal aorta (1-2 cm below the carina) to cardiac
apex. Sixty to 90 ml of iodinated contrast medium
(Optiray 350, Ioversol 350 mg /ml, Canada) was
injected intravenously via antecubital vein at a flow
rate of 5-8 ml/s followed by 50 ml of saline at a flow
rate of 5 ml/s. Retrospective ECG-gated reconstructions were routinely generated every 5% of the R-R
interval from 0% to 95% of the R-R interval. Among
these different data sets, we chose the best one to
evaluate existence, origin, calibration, and course.
In addition, the maximum intensity projection (MIP)
and volume rendering (VR) techniques, and the
unique display of globe views and 2D map (Philips
Extended BrillianceTM Workspace v 3. 0. 1. 3200,
Netherland) were used.
Definition and collection of coronary anomaly
The 4 main coronar y ar teries evaluated are
the left main coronary artery (LMCA), left anterior
descending arter y (LAD), left circumf lex arter y
(LCx) and right coronar y ar ter y (RCA). Nor mal
LMCA arises from the left coronary sinus, and is 5
to 10 mm in length. It passes leftward posterior to
the pulmonary trunk and bifurcates into the LAD
and LCx arteries. The LAD artery runs in the anterior interventricular groove and terminates near the
apex of the heart. It gives off diagonal branches to
the anterior free wall of the left ventricle and septal
branches to the anterior interventricular septum. The
LCx artery runs in the left atrioventricular groove.It
gives off obtuse marginal branches to the lateral left
ventricle. The RCA arises from the right coronary
sinus and runs rightward posterior to the pulmonary
outf low tract and then inferiorly in the right atrioventricular groove toward the posterior interventricular septum [2].
The anomalous coronary arteries we attempted
to collect include (1) absent LMCA. Absent LMCA
means the LAD and LCx arteries arise separately
[6]. (2) High take-off LMCA. It means origin of
LMCA gets off from the point above junctional zone.
(3) Ectopic origin of LMCA from right coronary
sinus. (4) Double LAD and ectopic origin of LAD
from RCA. (5) Ectopic origin of LCx from right
coronary sinus. (6) Ectopic origin of LCx from RCA,
absence of RCA. (7) Ectopic origin of RCA from
left coronary sinus. (8) Ectopic origin of RCA from
LAD. (9) Myocardial bridging. Coronary arteries
are normally located superf icial to myocardium.
Myocardial bridging is present when a segment of an
epicardial coronary artery runs through the myocardium rather than on the surface [8, 9, 10].
RESULTS
The incidence of anomalous anatomical origin
and course of the coronary arteries in our study was
15 % (n = 81). The anomalies found in our study
are absence of the left main coronary artery (n = 3,
0.5%) (Fig. 1a, 1b), high take-off origin of left main
coronary artery (n= 1, 0.2 %) (Fig. 2a, 2b), ectopic
origin of RCA from the left coronary sinus (n = 8,
1.5%) (Fig. 3a, 3b, 3c), and myocardial bridging (n
= 69, 12.6%). Among these 69 myocardial bridging
cases, 68 were located in proximal, middle and distal
portion of LAD (Fig. 4a, 4b, 4c), 1(1.4%) located
in proximal and middle LAD, 47(68.1%) located in
middle LAD, 6(8.7%) located in middle and distal
LAD, 14(20%) located in distal LAD. Only 1(1.4%)
located in terminal RCA (Fig. 5a, 5b). The mean
length of myocardial bridging is 10.2 mm (ranging
from 3.6 to 30.2 mm), and the mean depth is 2.2
mm (ranging from 1.0 to 5.6 mm). Thirty-five (51%)
Diagnosis of anomalous coronary arteries
1a
1b
113
1c
Figure 1. This is a 56 years old male who is absent of left main coronary artery (LMCA). a. Axial maximum intensity
projection image (slice thickness 5mm). Left anterior descending artery (LAD) and left circumflex (LCx) are arising
from the left sinus of Valsalva separately. b. Volume rendering display. LAD and LCx arteries are arising from the
left sinus of Valsalva separately. c. The globe view (slice thickness: 5mm) demonstrates the origin of coronary arteries
very well. (Ao: aorta)
2a
2b
of these cases underwent MDCT as part of health
examination, and 34 (49%) are for evaluation of suspicious coronary artery disease.
Discussion
Conventional coronary catheter angiography is
the standard to assess coronary artery disease, but
it has some limitations [2, 4, 7]. Coronary angiog-
Figure 2. This case is a 51 years
old male with high take-off left
main coronar y ar ter y (LMCA).
a. Volume rendering (VR) image
displays the origin of LMCA get
off from the point above junctional
zone between left coronary sinus
and the tubular part of the ascending aorta. b. Axial view can display left circumf lex artery (LCx)
and left anterior descending artery
(LAD) well while VR is hard to
display it. (Ao: aorta)
raphy is an invasive and expensive procedure. It only
selectively visualizes one vascular tree at a time and
it may be difficult to delineate the vascular tree due
to its complex 3D geometry displayed in 2D fluoroscopically. Another limitation is adequate procedure
and reading depends on the experiences of angiographers, and this causes a large percentage of coronary artery anomalies to be classified incorrectly on
conventional catheter angiography. However, novel
114
3a
Diagnosis of anomalous coronary arteries
3b
3c
Figure 3. This is a 29 years old female with ectopic origin of RCA (right coronary artery) from left coronary sinus.
a. Axial maximum intensity projection image (slice thickness 5mm). RCA is arising from the left sinus of Valsalva
and runs between aorta and pulmonary artery. b. Volume rendering display. RCA is arising from the left sinus of
Valsalva. c. The 2D map (slice thickness: 6mm) demonstrates the anomalous origin of RCA clearly. (Ao: aorta, PA:
pulmonary artery)
4a
4b
4c
Figure 4. Myocardial bridging locates at left anterior descending artery (LAD). a. Curved multi-planar reconstruction (cMPR) displays myocardial bridging in middle LAD (arrows) b. Sagittal maximum intensity projection image.
It displays the intramyocardial course and embedding in the myocardium of the middle LAD (white arrows). c.
Volume rendering displays from anterior view. Intramyocardial course and embedding into the myocardium of the
LV indicates left ventricle. (white arrow)
advances on MDCT provide a noninvasive technique and offer an accurate diagnostic modality to
visualize the origin and course of anomalous coronary arteries by a MIP and 3D VR display of heart
[2, 4, 5, 6, 7, 8, 11]. Recent developments in helical
CT technology had greatly increased its utility in
the evaluation of the coronary arteries [12]. With
overlapping reconstruction during the cardiac cycle,
Diagnosis of anomalous coronary arteries
5a
Figure 5. Myocardial bridging
locates at terminal RCA (right
coron a r y a r t e r y). It is r a re
with myocardial bridging at
RCA. a. Curved multi-planar
reconst r uct ion (cM PR) displays myocardial bridging in
terminal RCA. (white arrows)
b. Globe view. It helps to demon st r at e t he t e r m i n a l RCA
course embedded in the myocardiu m of the r ight at r iu m
(RA). (white arrow) (Ao: aorta,
RV: right ventricle, AM: acute
marginal artery)
5b
100(0-99% R-R interval) phases can be obtained.
The better temporal resolution and the ability to
choose the optimal cardiac phase result in a near cessation of physiologic motion
Common post-processing methods include MIP,
VR, cMPR, etc. 2D map and Globe view are unique
in Phillips, and it can help to demonstrate the origin
and course of coronary arteries very well. However,
it is not accurate to measure the length and depth of
myocardial bridging. The slab thickness is also an
important factor to display the images clearly.
An anomalous origin and course of the coronary
arteries can be benign or life threatening. The prevalence of coronary artery anomalies is about 0.3-1.2%
in angiography [1, 2, 6, 13], and in 0.3% of patients
at autopsy [14, 15]. The ratio of coronar y ar ter y
anomalies is 15% in our study. But when excluding
myocardial bridging, the number decreases to 2.4%.
Congenital coronary artery anomalies are the second
most common cause of sudden death due to structural heart disease in young athletes [15]. In particular, an anomalous vessel that crosses between the
aorta and the main pulmonary artery, either a left
coronary artery originating from the right sinus or a
right coronary artery emanating from the left sinus,
may be associated with a poorer outcome [15, 17].
In the past years, some studies have proposed a
possible anatomical-clinical classification of coronary artery anomalies that divides them into “minor”
and “major” according to their clinical relevance [18,
19, 20, 21]. In 2003, Rigatelli et al. [22] proposed a
more complete classification, which divided coronary artery anomalies into four classes based on
their clinical relevance (Table 1) [23, 24, 25], and
115
Table 1. Clinical relevance based classification of coronary artery
anomalies in the adults.
Class
Coronary artery anomalies
I-Benign
Ectopic origin of the LCx from the RS
Separate origin of the LCx and LAD
Ectopic origin of the LCx from the RCA
Ectopic coronary origin from the AO
Dual LAD type I- IV*
Myocardial bridge (score ≦ 5) ※
II-Relevant
Coronary artery fistula
Single coronary artery (R-L, I-II-III, A-P#)
Ectopic origin of the LCA from the PA
Atresic coronary artery
Hypoplastic coronary artery
III-Severe
Ectopic origin of the LCA from the RS
Ectopic origin of the RCA from the LS
Ectopic origin of the RCA from the PA
Single coronary artery (R-L, I-II-III, B# )
Myocardial bridge (score 5) ※
IV-Critical
Class II and superimposed CAD
Class III and superimposed CAD
LCx = left circumflex artery; RS = right sinus; LAD = left anterior
descending artery; RCA = right coronary artery; AO = ascending
aorta; LCA = left coronary artery; PA = pulmonary artery; LS
= left sinus; CAD = coronary artery disease, * according to the
classification Sindola-Franco et al. [23], ※ according to Angelini et al.
[24], # according to the classification of Lipton ea al. [25].
gave aids in management and clinical follow-up.
These 4 classification are benign, relevant, severe
and critical, and myocardial bridges are divided into
five groups (score 1-5) on the basis of their length
(<1 or >1 cm) and their reduction in diameter during
cardiac contraction (< 25%, 50% or >75%) [18, 24].
116
Diagnosis of anomalous coronary arteries
However, our cases were not classified into these
4 classes, because we could not divide myocardial bridges into 5 groups. The limitation is due to
motion artifacts during systolic phase, which caused
difficulty in assessing the ratio of cardiac contract.
Recognition of coronary anomalies is important
in patients who are going to undergo coronary catheter angiography, coronary interventions, and cardiac surgery. Some specific anomalies of the origin
and course of the coronary arteries have been recognized as a leading cause of sudden cardiac death,
especially in military recruits and young athletes [2,
3, 6, 26]. The patients in whom the aberrant arteries
pass between the main pulmonary artery and aorta
are at highest risk [27, 28]. Such patients may be
indicated in coronary artery bypassing grafting [29].
The coronary artery anomalies in this study are
discussed as following.
Absent LMCA
In 0.41% of cases, the left main artery is absent.
This anomaly contributes to 30.4% of all coronary
anomalies. If the LMCA is absent, one of the following may occur: (a) LAD and LCx arteries may
arise from the left sinus of Valsalva via separate
ostia, with both of normal length and course; (b)
the LCx artery may arise from the right sinus of
Valsalva or RCA and follow a course posterior to
the aorta; (c) LAD may arise from the right sinus of
Valsalva or RCA and follow either a septal course or
an anterior free wall course; or (d) LAD may arise
from the noncoronary aortic sinus, with its initial
portion posterior to the aorta and following a course
anteriorly toward its nor mal position [2]. In our
institution, the ratio of absent LMCA is 0.5% .This
anomaly is 3.7% of all coronary anomalies in our
study, which is 10 times lower than the result that
Duren et al. published [2], may be due to myocardial bridging including in our study. The anomaly of
myocardial bridging is 85% of all coronary anomalies in our study group.
High take-off of the LMCA
Vlodaver et al. reported that both coronary ostia
were situated above the sinutubular junction in 6% of
randomly selected adult hearts. High take-off of the
coronary arteries usually presents no major clinical
problems, but it may cause difficulty in cannulating
the vessels during coronary catheter angiography [10].
Ectopic origin of RCA from the left coronary sinus
Nor mal RCA arises from the right coronar y
sinus and runs rightward posterior to the pulmonary
outf low tract and then inferiorly in the right atrioventricular groove toward the posterior interventricular septum [2]. Ectopic origin of RCA from left
coronary sinus refers as abnormal RCA arises from
the left coronary sinus. Three subtypes of anomalous
origin of the RCA from the left coronary sinus are
classified based on the path of the anomalous artery
retroaortic, interarterial, and anterior to the pulmonary trunk [13]. Ectopic origin of RCA from the left
coronary sinus is uncommon, comprising less than
1% of all congenital coronary anomalies. It can cause
syncope, myocardial infarction, and sudden death
in the absence of a critical fixed stenosis. It significantly increases mortality rate for an anomalous
left coronary artery and RCA. A case of interarterial subtype possesses the highest risk of exerciseinduced ischemia, myocardial infarction, and sudden
death, and is regarded as malignant [14, 15]. A recent
study the authors observe that all of their patients
with anomalous left coronary artery died suddenly,
compared only 43% of patients with anomalous right
coronary artery, whereas the remaining 57% had
death unrelated to coronary artery anomaly [2].
The 8 cases of this group in our study group
are all interarterial subtype. Its ratio of all coronary
anomalies is 10% in our study. Seven of these subjects suffer from chest tightness on and off, but only
one had done cardiac catheterization. Five of these
seven cases had 50% stenosis at RCA orifice.
Myocardial Bridging
The incidence of myocardial bridge varies consistently between angiographic (0.5-2.5%) and pathologic (15-85%) series [30, 31]. Myocardial bridge is
most commonly localized in the middle segment of
the LAD artery [8, 32, 33, 34, 35].
Although it is silent in most cases, sometimes
it causes severe ischem ia. A ngi na , myoca rd ial
ischemia, myocardial infarction, left ventricular
dysfunction, myocardial stunning, and paroxysmal
at r iovent r icula r blockage, as well as exercise induced ventricular tachycardia and sudden cardiac
death, are accused sequels of myocardial bridging [2,
8]. Therefore, diagnosis and treatment of myocardial
bridging are important. Even when a few muscle
fibers cause myocardial bridging, MDCT can reveal
the vessel shifting into the myocardium. Besides, 3D
VR and cMPR (curved multi-planar reconstruction)
images make it possible to identify the anomaly. In
addition, MDCT helps to evaluate the incidence of
myocardial bridging in vivo [2]. In our study, the
Diagnosis of anomalous coronary arteries
incidence is 12.6%, which is 6 to 20 times higher
than that that according to findings of conventional
catheter angiography. It is probably because the aid
of 3D VR images can get better detection rate than
2D conventional catheter angiography.
Ou r results revealed an overall myocardial
bridge prevalence of 12.6%, which was closer to that
reported in autopsy studies, the ultimate gold standard for detecting this anomaly. However, even in
autopsy studies a wide variation of the incidence of
myocardial bridge has been reported, therefore the
difference between the results may be of the ethnicity or other factors. Further large series studies to
investigate the incidence would be helpful.
Searching for an anomalous orifice, selective
probing, and interpretation of vascular anatomy may
be difficult in catheter angiography. Conventional
catheter angiography does not provide any depth
information and is thus unable to provide the exact
3D course of the anomalous coronary artery [1, 2, 9,
36]. MDCT provides us a high quality and accurate
modality to visualize and diagnose coronary anomalies [2, 4, 6, 8, 9, 36].
One of the limitations in MDCT angiography
is the lack of hemodynamic information. Although
MDCT provides insight into the anatomy of the
aberrant artery and its surrounding structures, the
assessment of the cause of ischemia in these patients
is not yet easy. Various artifacts can degrade image
quality at coronary CT angiography [1, 7]. In addition, patients who had arrhythmia and poor breathholding can not be examined [2, 36].
In conclusion, MDCT with VR and MIP techniques, are useful and helpful for assessment of
anomalous coronary arteries for radiologist, cardiologist and surgeon. Comparing to other examinations
for displaying coronary artery anomaly, MDCT is
the modality of choices.

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Diagnosis of anomalous coronary arteries
64 切電腦斷層於冠狀動脈異常的診斷
侯貴圓 1　鄭慶明 1,2　劉雅萍 1　王梓軒 1　林恬敏 1　陳璽文 1　陳啟仁 1　莫元亨 1,2,3
國泰綜合醫院　放射線科 1
天主教輔仁大學　醫學院　醫學系 2
台灣大學　醫學院暨工學院醫學工程學研究所 3
冠狀動脈異常可分為良性及惡性（致命）兩類。以往這類異常大都由心導管診斷得知。有
別於侵入性的心導管檢查，新進的多切片電腦斷層檢查可提供非侵入性及高準確度的冠狀動脈
影像。本項檢查可利用三維影像顯示異常冠狀動脈的開口、走向及解剖位置。
我們從 2006 年 6 月到 2007 年 6 月收集了 540 位受檢者接受 64 切電腦斷層冠狀動脈血管
檢查的資料。這些受檢者包括接受健康檢查者及有心臟疾病病史的病人。結果診斷出有 81 位
受檢者有冠狀動脈異常。其中 3 位沒有左側冠狀動脈、1 位左側冠狀動脈屬高位開口、8 位右
側冠狀動脈開口異常，開口起源於左側冠狀竇，其它 69 位冠狀動脈有心肌橋異常。
雖然惡性的冠狀動脈異常很少導致死亡，但這項診斷對於心臟科醫師進行心導管檢查及外
科醫師實施手術有極大的貢獻，所以診斷出冠狀動脈異常是很重要的。利用 64 切電腦斷層的
容積重建（volume rendering，VR）及最大密度投影（Maximum Intensity Projection; MIP）可
清楚顯現冠狀動脈異常。與其他檢查方式相比，多切片電腦斷層是目前信賴度很高的診斷方式
之一。
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