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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 26, No 4, July/August 2015
172
AFRICA
the following: expansion of the stomach by the volume effect,
displacing it caudally, thereby increasing the distance between
the heart and the bowel; increased gastric emptying; stimulation
of liver clearance and peristaltic movement; and acceleration of
bile secretion and gallbladder emptying.
The aim of this study was to evaluate the efficacy of lemon
juice or milk administration compared to a control group, to
decrease infra-cardiac activity and to assess any resultant effect
on image interpretation of myocardial perfusion.
Methods
This was a prospective study. All patients 18 years and older
who were referred for MPI were invited to be enrolled in the
study. Ethics approval was obtained from the University of
the Witwatersrand’s Human Research Ethics Committee and
written consent was obtained from all study participants.
The study commenced in November 2009 and ran until May
2012. We recruited 904 patients but data from 274 patients were
excluded for various reasons [non-return for second day’s study,
milk or lemon juice not followed in a patient for both the stress
and rest study, and patients who fitted the exclusion criteria (Table
1)]. A total of 630 patients [304 female (48%) and 326 male (52%)]
aged 19–84 years were eventually enrolled for data analysis.
Patients were randomised into three groups. Group 0 (G0)
drank diluted lemon juice, group 1 (G1) drank full-fat milk, and
group 2 (G2) had no intervention (control group). Full-fat milk
consisted of 250 ml milk. Diluted lemon juice consisted of 50
ml lemon juice and 200 ml water, with a total volume of 250 ml.
Following the injection of 740 MBq
99m
Tc sestamibi during
stress, patients in G0 received diluted lemon juice and patients
in G1 received full-fat milk 20 minutes after the tracer injection,
whereas patients in G2 received no intervention. After the
rest injection of 740 MBq of
99m
Tc sestamibi, patients in G0
received diluted lemon juice and patients in G1 received milk,
immediately after the tracer injection, whereas patients in G2
received no intervention.
Stress test protocol
A routine two-day protocol was used. Patients were stressed on
day one and a rest study was done on day two. Patients were fasted
for at least four hours prior to stress testing (usually overnight)
and were required to abstain from caffeine-containing beverages
and methylxanthine-containing medications for at least 24 hours.
Caffeine and methylxanthines block the adenosine receptors on
arterial smooth muscle cells, thereby limiting the effectiveness
of vasodilator agents. Our department’s protocol is that we
withhold caffeine in all patients, even if exercise stress is planned,
in case there is a necessity to switch to pharmacological stress.
Beta-blockers and calcium channel antagonists were withheld,
where appropriate. The patients were haemodynamically and
clinically stable for 48 hours prior to the test.
The stress modality (treadmill, dipyridamole or dobutamine)
was chosen and implemented in accordance with the recent
EANM guideline.
17
Routine imaging for stress is carried out
30–45 minutes post tracer injection, however in our study some
patients were imaged later due to the longer acquisition times
with the addition of prone imaging, which is also a routine
protocol in our department. All patients were imaged supine
with their arms raised. Gated prone images were acquired after
the gated supine stress images. The routine rest images were
acquired 45–80 minutes post injection.
Imaging protocol
SPECT imaging was performed using a double-head, rotating,
large field-of-view gamma camera (GE Medical Systems
Infinia hybrid system), equipped with a low-energy, high-
resolution collimator. SPECT images were acquired on a 64
×
64 matrix. Sixty images (25 seconds for rest, 20 seconds for
stress) were obtained over a semi-circular 180° arc. Filtered back-
projection was performed with a low-resolution Butterworth
filter and no attenuation or scatter correction was applied.
Transaxial tomograms were reconstructed and the images were
re-orientated into three sets of orthogonal slices, including short
axis, horizontal long axis and vertical long axis for each study.
Data analysis
Two experienced nuclear medicine physicians (total experience
30 years) evaluated the raw data of the anterior (Ant) and left
lateral (LLAT) views of both the stress and rest studies for the
presence or absence of interfering infra-cardiac activity. Slice
numbers 15 and 45 of the planar display from the SPECT
acquisition were used in all patients to increase reproducibility.
Slice 15 was chosen because of the best visualisation of the
inferior wall of the left ventricle in the anterior projection,
and likewise, slice 45 displayed the best projection for the
inferior wall of the left ventricle in the lateral view. Observers
evaluated the images simultaneously and were blinded to the
clinical information as well as the protocol details. If there was a
disagreement with the values obtained, a consensus was reached.
The observers used visual and semi-quantitative assessment
of the raw data of both stress and rest images, as previously used
by Hofman
et al.
8
Visually, any presence of infra-cardiac activity
was graded as ‘yes’ and the absence of infra-cardiac activity was
graded as ‘no’. If the infra-cardiac activity was equal to lung
background, it was described as absent. If infra-cardiac activity
was present, it was graded as follows: 0: absence of infra-cardiac
activity; 1: infra-cardiac activity less than myocardial activity;
2: infra-cardiac activity equal to myocardial activity; 3: infra-
cardiac activity greater than myocardial activity (Fig. 1).
Table 1. Inclusion and exclusion criteria
Inclusion criteria
Exclusion criteria
• Patients older
than 18 years
of age
• Patients
referred for
99m
Tc sesta-
mibi myocar-
dial perfusion
imaging
• Lactose intolerance
• Patients who failed exercise stress testing and
had a contra-indication to pharmacological
stress testing, i.e. using vasodilators and dobu-
tamine
• Unable to drink 250 ml of fluids secondary to
medically essential fluid restriction
• Pregnant patients
• Previous cholecystectomy, liver or biliary
system disease
• Peptic ulcer disease within the last six months
• History of diabetes mellitus
• Previous myocardial infarction within the last
two months, unstable angina, severe primary
valvular disease, left ventricular aneurysm,
primary cardiomegaly, left ventricle hypertro-
phy or severe conduction disturbances