CARDIOVASCULAR JOURNAL OF AFRICA • Vol 24, No 7, August 2013
256
AFRICA
and Planning Committee of our hospital.
All vasoactive medications were withheld for at least 12 hours
before the study, and all long-acting vasoactive medications
were withheld for at least 24 hours. Alcohol and caffeine were
prohibited within 12 hours of the study. Patients who had a
smoking history refrained from smoking at least 48 hours before
the study to prevent any relevant effect of smoking.
Patients with unstable angina, severe cardiac failure, additional
cardiac (valvular, congenital, etc) or peripheral vascular disease,
renal and hepatic dysfunction, uncontrolled hypertension, or
any other condition that would preclude withholding vasoactive
medications, and patients taking antioxidant vitamin supplements,
oestrogen replacement therapy or allopurinol were excluded
from the study.
Study protocol and radial artery image with
ultrasound studies
The vasodilator response in the radial artery was determined
from two-dimensional ultrasound images by an evaluator blinded
to the study. The images were obtained with the use of a
7.0-MHz linear-array transducer (model SSA-770A Ultrasound
System; Toshiba, Tokyo, Japan). Examination was performed
with the patient resting supine for at least five minutes in a quiet
setting. For each patient, radial artery images were obtained 2
and 5 cm above the radial styloid. This location was marked, and
all subsequent images were obtained at the same location.
Images were recorded on a super-VHS videocassette recorder
and radial artery diameters were measured from the tape with
ultrasonic calipers. Measurements of radial artery diameter were
taken from the anterior to the posterior interface between the
media and adventitia at end-diastole, incident with the R-wave,
on a continuously recorded ECG. The measurements were
performed by one observer who was blinded to the details. At the
moment of measurement, arterial blood pressures were checked
for the safety of the study and were found normal (120/80
mmHg) in all patients.
In all patients, first, baseline Doppler ultrasound images were
obtained (measurement 1: D1, FV1, A1). The radial artery of
the non-dominant arm was scanned in transverse section and the
lumen diameter (D1) was measured. Then, flow volume (FV1)
and lumen area (A1) were measured in longitudinal section and
all measurements were recorded.
Second, a blood pressure cuff, placed at the proximal portion
of the arm, was inflated to occlusive pressure (200 mmHg),
and occlusion was maintained for five minutes to induce
hyperaemia. The cuff was then rapidly deflated and pulsed
Doppler signals and measurements were recorded at the moment
of cuff deflation for 15 seconds (measurement 2: D2, FV2, A2).
Finally, two-dimensional and pulsed-Doppler measurements
were again obtained and recorded 60 seconds after cuff deflation
(measurement 3: D3, FV3, A3).
In group l, patients were then given 2 g oral vitamin C
(Redoxon, Bayer, Germany, 1 000-mg tablets) and a repeat
radial ultrasound study was performed two hours after oral
administration to evaluate its effect on radial artery vasodilation
in the first 31 patients. These measurements were accepted as
study measurements for group 1 (measurements 4, 5, 6 for group
1: D4, 5, 6; FV4, 5, 6; A4, 5, 6).
In group 2, the next 31 patients were given orally 2 g vitamin
C and 600 IU vitamin E (Ephynal, Roche, France, 300 IU, oral
capsules), and a repeat radial ultrasound study was performed
two hours after oral administration to evaluate their effects on
radial artery vasodilation. These measurements were accepted as
study measurements for group 2 (measurement 4, 5, 6 for group
2: D4, 5, 6; FV4, 5, 6; A4, 5, 6). In group 3, patients took no
medication and the measurements were repeated.
Finally, the increasing values of D, FV and A of the two
study groups were compared and the mean difference of their
increasing values was measured (Table 1). In the control group,
the results of the measurements were almost the same and there
was no statistically significant difference between measurements
(
p
>
0.05).
Statistical analysis
Results were analysed using SPSS software (SPSS 18.0.1 for
Windows; SPSS, Chicago, IL, USA). Comparisons of groups
were performed with the Student’s
t
-test and non-parametric
Mann-Whitney
U
-test for continuous variables and the Fisher
exact test for discrete variables, as appropriate. Pre–post
comparisons with paired observations were analysed using the
Wilcoxon signed-ranks test.
Linear regression models were built with least-squares
methods using all variables and also with a backward elimination
approach, starting with all variables that were significant (
p
<
0.05) in univariate relationships and eliminating variables with
p-
values greater than 0.05, in a stepwise fashion.
Results
Ninety-three patients were included in the study from 1 February
to 31 August 2008. Patient characteristics are summarised in
Table 2. Median age, male/female gender, and left ventricular
ejection fraction were similar in the three groups (
p
>
0.05). The
presence of diabetes was similar in the study groups, but scarce
in the control group. A history of smoking in the vitamin C group
TABLE 1. INCREASINGVALUES OF FLOWVOLUME,
AREAAND DIAMETER
Vitamin C
(mean value)
Vitamin C+E
(mean value)
p
-value
FV4–FV1
1.322
1.677
0.542
A4–A1
8.096
7.929
0.952
D4–D1
2.225
2.548
0.651
FV5–FV2
2.322
2.354
0.968
A5–A2
9.064
13.364
0.211
D5–D2
2.225
2.741
0.454
FV6–FV3
1.322
1.871
0.378
A6–A3
6.612
10.806
0.378
D6–D3
2.225
2.387
0.790
FV1, FV4, baseline flow volume before and after drug intake, respec-
tively; FV2, FV5, flow volume at the moment of cuff deflation before
and after drug intake, respectively; FV3, FV6, flow volume 60 seconds
after cuff deflation before and after drug intake, respectively. A1, A4,
baseline area before and after drug intake, respectively; A2, A5, area at
the moment of cuff deflation before and after drug intake, respectively;
A3, A6, area 60 seconds after cuff deflation before and after drug intake,
respectively. D1, D4, baseline diameter before and after drug intake,
respectively; D2, D5, diameter at the moment of cuff deflation before and
after drug intake, respectively; D3, D6, diameter 60 seconds after cuff
deflation before and after drug intake, respectively.
