CARDIOVASCULAR JOURNAL OF AFRICA • Vol 21, No 5, September/October 2010
AFRICA
287
A stress thallium test was done which did not show ischae-
mia. An MDCT (Light Speed VCT; GE Healthcare, Milwaukee,
Wisconsin, USA) was performed and the diagnosis was
confirmed (Fig. 2).
Discussion
Coronary artery anomalies are present at birth, but relatively few
are symptomatic during childhood and later in life. Yamanaka
et
al
. reported that only 20% of them are clinically significant.
1
The
LCX originating from the right sinus of Valsalva or as a proximal
branch of the RCA is the second most common anomaly of the
coronary arteries, with a reported incidence of 0.30 to 0.67%.
17
On the other hand, absence of the LCX and a super-dominant
RCA crossing the crux, ascending to the left atrio-ventricular
groove and running the length of the LCX as a terminal exten-
sion of the RCA is an extremely rare entity, with a reported
incidence of 0.003%.
1
Because of different therapeutic options, a congenitally
absent coronary artery must be distinguished from a totally
occluded coronary artery that fills from another coronary artery
via collaterals. Although an experienced operator can easily
differentiate the two conditions, it is worth remembering the key
issues. Firstly, coronary collaterals may be totally occluded, but
not in a case of a congenitally absent coronary artery. Secondly,
with total occlusion there are usually wall motion defects in the
left ventricle, but not with a congenitally absent coronary artery.
In addition, the largest vessel segment is usually the proximal
segment of the totally occluded artery. However, in a congenital-
ly absent coronary artery, the distal anastomotic segment seems
to be the largest and the proximal segment may be relatively
thinner. Therefore, in total occlusion, the proximal end of the
artery ends sharply, whereas there is a tapered end of the vessel
in congenital cases.
18
The absence of the circumflex artery was first described by
Baressi
et al
.
2
in 1975 and to our knowledge, our case is the 17th
in the literature. (The four patients in Yamanaka’s study and two
patients in that of Komatsu are not included.)
1-16,19
Except for one
patient with myocardial infarction (but with no obvious narrow-
ing of the coronary artery)
3
and one patient with the co-existence
of dilated cardiomyopathy,
4
this abnormality is considered a
benign congenital anomaly.
Itoi
et al
. found an abnormally low coronary flow reserve in
the RCA of a 13-year-old patient with an absent LCX but no
ischaemia on a treadmill test and no ischaemic area in the LCX
region with a thallium test.
6
Kursaklıoglu
et al
. has followed up
on a patient with a Cx artery originating from the distal right
coronary artery for 13 years and has reported a benign course.
8
They also report that a thallium perfusion scan is superior to
an exercise ECG for clinical decision making and follow up on
these patients. In our patient, a normal stress thallium test and the
absence of any plaque in the coronary arteries on angiography
indicated the benign nature of this anomaly.
Although conventional cardiac catheterisation is a well-known
test for the detection of coronary anomalies, the multi-detector
row CT (MDCT) is emerging as an essential
imaging tool for
evaluating coronary arteries, as many of the congenital coronary
anomalies are easily assessed with this modality.
20
Because of
its three-dimensional nature, MDCT is well suited to detect and
define the anatomical course of coronary artery anomalies and
their relationship to other cardiac and non-cardiac structures. The
robust visualisation and classification of anomalous coronary
arteries make CT angiography a first-choice imaging modal-
ity for the investigation of known or suspected coronary artery
anomalies.
21
The incidence of congenital absence of the left circumflex
artery may be expected to be higher after wide usage of MDCT,
however, Komatsu
et al
. reported only two cases (0.05%) of this
type of anomaly in their 3 910 consecutive cases undergoing
MDCT.
19
This suggests the anomaly remains rare, even in the
era of MDCT.
Conclusion
The absence of the LCX with a super-dominant RCA running
the full course of the LCX is a very rare anomaly and is not
associated with adverse events. MDCT is a suitable non-invasive
imaging modality for detecting congenital coronary anomalies.
References
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21
:
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Fig. 2. The circumflex artery is absent and only the left
anterior descending artery is seen in the multi-detector
computed tomography. (A) The left circumflex artery
is absent in this view and the left anterior descending
artery is clearly visualised. (B) A super-dominant right
coronary artery is seen. The terminal portion of the right
coronary artery unusually continues in the region of the
left circumflex artery.
A
B
