CARDIOVASCULAR JOURNAL OF AFRICA • Vol 21, No 3, May/June 2010
AFRICA
143
antral and duodenal motilin receptors. This leads to strong phase
3 contractions of the interdigestive motor complex.
7
In addition,
some studies have suggested that erythromycin stimulates gall
bladder motility.
10
In our study, we sought to determine whether taking oral
erythromycin prior to SPECT myocardial perfusion imaging
with Tc99m-sestamibi would reduce the amount of interfering
extra-cardiac activity and improve image quality and patient
management. An additional aim was to validate the recently
described method to quantify the level of interfering extra-
cardiac activity – the MYO:EXT ratio.
11
Methods
Study participants were patients who were routinely referred
for myocardial perfusion imaging for known or suspected coro-
nary artery disease at the Nuclear Medicine Department of the
Steve Biko Academic Hospital (formerly known as the Pretoria
Academic Hospital). Patients were evaluated for possible exclu-
sion criteria, after which written consent was obtained from all
study participants. See Table 1 for inclusion and exclusion crite-
ria. A list of possible interactions with erythromycin was made
available to all study participants (Table 2).
The study commenced following ethics approval and 101
patients were enrolled in the study between 19 May and 22
September 2008. Four patients were excluded from the study due
to incomplete data and one was unable to complete the study due
to severe nausea and hypotension (Fig. 1). Clinical characteris-
tics of patients in both groups are listed in Table 3.
Both the allocation of patients as well as the administration
of the interventions was administered by the nursing staff of
the department. All physicians were blinded to the detail of the
protocol. Patient preparation consisted of the following: at least
a four-hour fast prior to stress testing (usually overnight), no
caffeine for at least 24 hours and discontinuation of
β
-blockers,
calcium channel blockers, nitrates and any other drugs consid-
ered necessary. Patients were verbally checked for abstinence
from these substances prior to the study.
Patients who were allocated to group A received 500 mg of
non-enterically coated erythromycin orally one hour prior to
image acquisition.
7,12
Where such patients required aminophyl-
line, the dose was reduced to 75 mg intravenously (IV) (erythro-
mycin metabolite increases the plasma level of aminophylline by
35%).
13
Patients allocated to group B received 250 ml of diluted
lemon juice (150 ml lemon juice
+
100 ml water) 10 min after
tracer injection, which is the standard of care in our department
(as validated by Cherng
et al
.
9
) Fig. 2 shows the randomisation
process.
A two-day protocol was performed with IV injection of 555
MBq of Tc99m-sestamibi on both days and study participants
underwent mostly pharmacological stress testing (0.56 mg/kg
dipyridamole IV) combined with low-level exercise. Stress imag-
es were acquired 30 min after tracer injection and rest images
between 45 and 60 min following tracer injection.
Image acquisition and processing
Patients were imaged supine using a double-headed Siemens
E-CAM gamma camera with both detectors configured at 90˚
TABLE 1. INCLUSIONAND EXCLUSION CRITERIA
Inclusion criteria
Exclusion criteria
Patients who were routinely
•
•
referred for myocardial perfu-
sion imaging for known or
suspected coronary artery
disease at the Nuclear Medi-
cine department of the Steve
Biko Academic Hospital.
(Previously known as the
Pretoria Academic Hospital.
Pregnancy
•
•
Patients younger than 18 years
•
•
of age
Known hypersentivity to
•
•
erythromycin
Patients using gastric motility
•
•
agents which could poten-
tially cause the gallbladder to
contract
Previous billiary or gastro-
•
•
intestinal surgery
Hepatic impairment
•
•
Significant history of upper
•
•
gastro-intestinal complaints
Patients using essential medi-
•
•
cation with known erythromy-
cin interactions.
TABLE 2. POSSIBLE DRUG INTERACTIONS
WITH ERYTHROMYCIN
Digoxin
•
•
Tacrolimus
•
•
Sildenafil
•
•
Cyclosporine
•
•
Dispoyramide
•
•
Lovastatin or simvastatin
•
•
Warfarin
•
•
Bromocriptine
•
•
Theophylline
•
•
Cilostazol
•
•
Alprazolam or triazolam
•
•
Quinidine
•
•
Ergotamine
•
•
Vinblastine
•
•
Carbamaepine
•
•
Other antibiotics
•
•
TABLE 3. CLINICAL CHARACTERISTICS OF
PATIENTS IN EACH GROUP
Erythromycin
(
n
=
45)
Lemon juice
(
n
=
51)
p
-value
Age (mean)
59.04
58.10
0.631
Gender (male/female)
33/12
35/16
0.738
Caucasian
34
35
0.345
Black
6
9
Indian
5
4
Coloured
0
3
Co-morbidities
Acute coronary syndrome
40
45
0.849
Systemic hypertension
36
40
0.984
Diabetes mellitus
10
12
0.833
Dyslipidaemia
31
19
0.006
CVS failure
10
7
0.300
101 patients
fulfilled criteria
4 patients with incomplete
data (3 E, 1 L)
1 patient with poor clinical
condition (E)
Erythromycin
(45 patients)
Lemon juice
(51 patients)
Fig. 1. Study protocol.
