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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 28, No 1, January/February 2017
AFRICA
17
Discussion
Arterial blood pressure has a daily circadian rhythm.
Physiologically, nocturnal blood pressure decreases by more
than 10% compared to day-time levels, and this is called dipper
hypertension. If the nocturnal blood pressure has a less than
10% fall from day-time blood pressure values, it is considered as
non-dipper hypertension.
10
The reason for such classification is
due to the differences in morbidity and mortality rates between
these groups. In patients who have non-dipper blood pressure,
end-organ damage (ventricular hypertrophy, microalbuminuria,
decreased arterial compliance) as well as cardiovascular
morbidity and mortality rates are higher.
11,12
In order to develop a standard index for coronary blood flow
measurement, Gibson
et al
. presented the TIMI frame count
as a simple, productive, objective and quantitative technique
by investigating the angiographic images of the TIMI-4 study.
8
After administration of an opaque material, the TIMI square
count is the sum of the ciné-angiographic squares seen between
the level of the stained coronary artery ostium and its distal part
on CAG. A high TIMI frame count is related to a slow flow rate
and endothelial dysfunction.
13
In our study, we compared the
TIMI frame count in dipper and non-dipper hypertensive patient
groups who had normal CAG.
According to a study by Yazici
et al
., the number of
non-dipper patients was significantly higher than dipper patients
in a patient group with slow coronary flow rates. In that study,
the non-dipper patients with slow coronary flow rates had a
higher percentage of unstable angina-like features, recurrent
chest pain, frequency of malignant ventricular arrhythmia and
sudden cardiac death rates than dipper patients.
14
Evola
et al
. compared the TIMI frame counts of 80
hypertensive patients with normal CAG with 15 normotensive
subjects, and found higher TIMI scores in the hypertensive
group. In the same study, when the hypertensive patients with
negative and positive myocardial perfusion scintigraphy were
compared, the TIMI frame counts were significantly higher
in patients with positive scintigraphy.
15
From these data, they
predicted that coronary artery flow and myocardial perfusion
disorders were more frequent in the group with high TIMI frame
counts. They concluded that myocardial perfusion scintigraphy
could be used as a non-invasive diagnostic test to determine early
changes in coronary microcirculation.
In our study, we found a higher TIMI frame count in all
three coronary arteries in the non-dipper hypertensive patient
group compared to the dipper group. In their study showing the
significance of small-vessel disorder, Pekdemir
et al
. investigated
the coronary anatomy using intravascular ultrasonography
(IVUS) and epicardial resistance with fractional flow reserve
(FFR).
16
They stated that in patients with slow coronary flow, the
increase in resistance in epicardial coronary arteries could play a
role in the development of early diffuse atherosclerosis.
In a patient group with slow coronary flow, Xia
et al
.
discovered higher serum uric acid, platelet count, high-sensitivity
C-reactive protein (CRP) and two-hour fasting glucose levels
compared to the control group.
17
In recent epidemiological and
experimental studies, a high uric acid level has been proven to be
a cardiovascular risk factor.
18,19
Using the TIMI frame count, Turhan
et al.
compared
coronary blood flow in 42 metabolic syndrome patients and a
control group of 42 subjects without the metabolic syndrome.
The TIMI frame count was statistically significantly higher in
patients with higher values of waist circumference, body mass
index and triglyceride levels.
20
In our study, the body mass index
was statistically significantly higher in the non-dipper group than
in the dipper group.
According to numerous robust evidence, deterioration of
endothelial-dependent vasodilatation as a result of a decrease
in nitric oxide release in brachial, coronary, renal and small
arteries is a risk factor in cardiovascular and cerebrovascular
patients.
21-26
Higashi
et al.
compared endothelial dysfunction in 20
non-dipper and 20 dipper hypertensive patients.
27
The endothelial
dysfunction predictors were decreased nitric oxide final products,
nitrite/nitrate and cyclic guanicine monophosphate in 24-hour
urine samples. In the non-dipper patient group, nitrite/nitrate
and cyclic guanicine monophosphate levels in 24-hour urine
samples were statistically significantly lower. If we consider the
TIMI frame count as a predictor of endothelial dysfunction,
finding a higher TIMI frame count in all three coronary arteries
confirms the study by Higashi
et al.
27
Table 3. Comparison of ambulatory blood pressure data
between the groups
Ambulatory blood pressure
Dipper
group
(
n
=
30)
Non-dipper
group
(
n
=
30)
p
-value*
Pulse (bpm
±
SD)
66.57
±
4.92 72.70
±
4.86
0.001
Over 24 hours
Mean systolic BP
(mmHg
±
SD)
118.93
±
14.8 124.37
±
19.23 0.226
Mean diastolic BP
(mmHg
±
SD)
68.76
±
10.55 69.53
±
8.64 0.749
Day-time
Mean systolic BP
(mmHg
±
SD)
123.47
±
16.67 124.63
±
19.08 0.802
Mean diastolic BP
(mmHg
±
SD)
71.87
±
11.49 69.67
±
9.21 0.417
Night-time
Mean systolic BP
(mmHg
±
SD)
108.10
±
13.61 123.50
±
20.49
0.001
Mean diastolic BP
(mmHg
±
SD)
60.60
±
8.94 69.13
±
8.3
<
0.001
Systolic BP variation
(%
±
SD)
13.33
±
4.47 1.32
±
5.49
<
0.001
Diastolic BP variation
(%
±
SD)
15.57
±
5.74 2.03
±
6.03
<
0.001
Continuous data are expressed as mean
±
SD.
*Independent samples
t
-test, statistical significance level is
p
<
0.05
(bold values)
BPM: beat per minute, SD: standard deviation, BP: blood pressure.
Table 4. Comparison of TIMI frame scores between the groups
TIMI fram scores
Dipper
group
(
n
=
30)
Non-dipper
group
(
n
=
30)
p
-value*
RCA TIMI frame score
16.83
±
3.70 21.63
±
3.44
<
0.001
Cx TIMI frame score
21.28
±
3.52 25.65
±
3.61
<
0.001
LAD TIMI frame score
34.20
±
2.80 37.05
±
3.30
0.001
LAD corrected TIMI frame score 20.05
±
1.63 21.74
±
1.95
0.001
The average TIMI frame score 19.31
±
2.31 22.94
±
2.61
<
0.001
Continuous data are expressed as mean
±
SD.
*Chi-squared test, statistical significance level is
p
<
0.05 (bold values).
RCA: right coronary artery, TIMI: thrombolysis in myocardial infarc-
tion, Cx: circumflex artery, LAD: left anterior descending artery.