CARDIOVASCULAR JOURNAL OF AFRICA • Vol 24, No 9/10, October/November 2013
352
AFRICA
Exclusion criteria were severe arrhythmia, previous serious
allergic reaction to the contrast medium, pregnancy, and renal
and respiratory failure. None of the patients had repeat CT
scans. The indications for MSCT scans included the presence
of chest pain, abnormal stress testing, the presence of ischaemia
on non-invasive tests, coronary artery disease screenings and the
determination of patency of bypass grafts or stents.
Patients received a 50- to 100-mg oral dose of metoprolol one
hour prior to the scan, with additional intravenous (IV) metoprolol
administered immediately prior to the scan if necessary. The
target heart rate (HR) was less than 70 beats per minute, under
close cardiac monitoring for heart rate and blood pressure. If
necessary, oral alprazolam (0.5–1 mg) was administered 60 min
prior to the procedure. All patients received sublingual isosorbide
dinitrate immediately prior to starting the scan protocol.
Computed tomography coronary angiography was carried
out using a 64-MSCT scanner (General Electric Light Speed
VCT scanner, Waukesha, WI, USA) after IV injection of 80 ml
of non-ionic contrast medium (Iopamiro 370; Bracco, Milan,
Italy) as a bolus dose at a rate of 6 ml/s with retrospective ECG
gating. The scan field was extended from the proximal aorta to
the cardiac apex.
The imaging parameters were as follows: detector collimation
of 64 × 0.625 mm, tube voltage 120 kV, current 500–800 mA,
gantry rotation time 350 ms, pitch 0.20, and slice thickness
0.625 mm. Retrospective ECG-gated images were obtained
during one held breath. These images were evaluated with multi-
planar reconstruction, maximum-intensity projection and three-
dimensional volume-rendering methods. The 75% phase during
diastole was found to be optimal for the analysis of anomalies
of the left coronary arteries. The right coronary artery (RCA)
was evaluated at either the 45 or 75% phase of the cardiac cycle,
depending on which phase presented the least amount of motion.
Results
Of the 745 patients, 276 were female and 449 were male. The
mean age was 54.9
±
11.3 years. The indications for MSCT
scans included the presence of chest pain (
n
=
250, 33.5%), or
ischaemia on non-invasive tests (ECG, treadmill stress test or
myocardial perfusion scintigraphy) (
n
=
153, 20.5%), coronary
artery disease screenings (
n
=
220, 29.5%), and the determination
of patency of bypass grafts (
n
=
76, 10.2%) or stents (
n
=
46,
6.1%). The incidence of diabetes, hypertension, hyperlipidaemia,
family history and smoking were 14.7, 34.4, 34.7, 9.3 and 23.2%,
respectively. The patients’ characteristics are shown in Table 1.
Six patients with CCAs, and 16 with MB had atypical chest
pain and dyspnoea. None of the patients with CCAs or MB
suffered from syncope.
Right dominance was observed in 563 patients (75.5%),
balanced dominance in 110 (14.7%), and left dominance in 72
patients (9.6%). We identified 176 patients who had evidence
of either a coronary anomaly (4.42%,
n
=
33) or myocardial
bridging (19.1%,
n
=
143) (Table 2). The majority of patients
with coronary anomalies were male (63.63%,
n
=
21).
The patients with detected coronary anomalies included
eight with the conus artery originating separately from the right
coronary sinus (RCS) (1.07%), seven with absence of the left
main artery (0.93%), seven with a superior right coronary artery
(RCA) (0.93%), four with the circumflex artery (CFX) arising
from the RCS (0.53%), two with the CFX originating from the
RCA (0.26%), one with a posterior origin of the RCA (0.13%),
one with a coronary fistula from the left anterior descending
artery and RCA to the pulmonary artery (0.13%), and one
with a coronary artery aneurysm (0.13%). Atherosclerosis was
observed in four patients with an anomalous CFX arising from
the RCA and five with a superior RCA. The other patients with
coronary anomalies did not have any atherosclerosis.
Of the six patients with anomalous origins of the CFX from
either the RCA or RCS, three patients had mild atherosclerosis
in all the coronary arteries including the anomalous CFX, one
had atherosclerosis in only the anomalous CFX, and one had
atherosclerosis in the other vessels but not in the anomalous
CFX. One patient with an anomalous CFX did not have any
atherosclerosis in any coronary artery. Four patients with a
superior RCA had atherosclerosis in the anomalous and normal
vessels, and one had atherosclerosis in only the superior RCA.
One patient with a superior RCA origin had atherosclerosis in
the normal originating coronary arteries but not in the anomalous
RCA. One patient had no atherosclerosis in any of the vessels.
One patient with a superior origin had a history of stenting, both
in the superior RCA and the left anterior descending (LAD)
artery. One patient with a posterior RCA had no atherosclerosis
in the anomalous or normal vessels or the coronary arteries.
Myocardial bridging was mostly observed in the LAD
(93.7%,
n
=
134), intermediate artery (1.39%,
n
=
2), obtuse
margin artery (1.39%,
n
=
2), first diagonal artery (0.6%,
n
=
1),
second diagonal artery (0.6%, n
=
1) and RCA (0.6%,
n
=
1). In
total, myocardial bridging was observed in 19.1% of the patients
(
n
=
143) (Table 3).
TABLE 1. PATIENTS’ CHARACTERISTICS*
Characteristics
Number
%
Female
276
37
Male
449
60.2
Hypertension
257
34.4
Hyperlipidaemia
258
34.6
Diabetes
110
14.7
Smoking
173
23.2
Prior stenting
46
6.1
Prior bypass
76
10.2
*Median age
±
SS
=
54.9
±
11.3 years.
TABLE 2. CORONARYANOMALIES
Number
Incidence (%) Anomalies (%)
Benign anomalies
CA from RCS
8
1.07
24.24
Absence of LMA
7
0.93
21.21
Posterior RCA
1
0.13
3.03
Potentially clinically significant anomalies
Superior RCA
7
0.93
21.21
CFX from RCS
4
0.53
12.12
CFX from RCA
2
0.26
6.06
Coronary fistula
1
0.13
3.03
Coronary aneurysm
1
0.13
3.03
CA: conus artery; RCS: right coronary sinus; LM: left main artery;
RCA: right coronary artery.
