CARDIOVASCULAR JOURNAL OF AFRICA • Volume 25, No 1, January/February 2014
6
AFRICA
calcification (
p
=
0.2). Furthermore, there was no difference
in the absolute difference between ambulatory systolic blood
pressure and CASP values between those with and without
coronary calcification (difference
=
8.27 and 8.16, respectively,
p
=
0.8).
Fig. 1 shows the correlation of office with ambulatory
systolic blood pressure. Office systolic blood pressure and CASP
correlated well with their ambulatory measurement (both
r
=
0.90).
Discussion
This was an observational study of 75 consecutive patients
undergoing dialysis in a South African public sector unit. The
cohort was young with a low level of co-morbidity due to
stringent criteria for the selection of dialysis patients.
A key finding in this study was that both coronary and
abdominal aortic calcification was not associated with a higher
CASP relative to the brachial systolic blood pressure. This ratio
was used to control for systolic blood pressure, which would
otherwise make comparison between groups difficult. Since
the study had an 80% power to detect a difference of
>
3% in
CASP, it was unlikely that there would be a clinically meaningful
difference between CASP values with and without calcification.
The reasons for these findings are unclear but may be that
Table 1. Baseline characteristics of patients
(
n
=
74 unless otherwise indicated)
Characteristic
Value
Range
(SD/IQR)
Age, mean (years)
41.8
10.5
Women (%)
56.8
Months on dialysis, median
32.0
43.6
Diabetes (%)
13.5
Tobacco use (%)
41.9
History of cardiovascular disease (%)
4.0
Office systolic BP (mmHg)
146.8
28.0
Office diastolic BP (mmHg)
95.2
17.6
ABPM systolic BP
a
(mmHg)
147.4
33.1
ABPM diastolic BP
a
(mmHg)
97.6
21.7
ABPM peripheral pulse pressure
a
(mmHg)
49.8
15.4
ABPM central aortic systolic pressure
a
(mmHg)
139.2
31.3
ABPM dipping status
a
(%)
5.3
5.5
LVMI (g/m
2
)
180.4
97.4
LVH
By ECHO
86.4
By ECG
70.3
Number of antihypertensives used, mean
2.3
1.4
SD, standard deviation; IQR, interquartile range; ABPM, ambulatory
blood pressure monitoring; BP, blood pressure; LVMI, left ventricular
mass index; LVH, left ventricular hypertrophy.
a
n
=
72.
Table 2. Baseline characteristics by presence of vascular calcification
Coronary calcification
Abdominal aortic calcification
Variable
n
CAC
–
n
CAC
++
p
-value
n
AAC
–
n
AAC
++
p
-value
Age (median)
43
38.3 27
46.0 < 0.01 47
39.3 26
46.0 < 0.01
Gender, m:f ratio
43
1.1 27
0.5 0.1
47
1.0 26
0.4 0.1
Tobacco use (ever) (%)
43
37.2 27
51.9 0.2
47
34.0 26
57.7
0.1
Prior cardiovascular events (%)
43
2.3 27
7.4 0.3
47
4.3 26
3.9 0.9
Presence of diabetes (%)
43
7.0 27
25.9 < 0.05 47
4.3 26
30.8 < 0.01
Office systolic BP (mmHg)
43 145.5 26 149.0
0.6
46 144.1 25 152.8
0.2
Office diastolic BP (mmHg)
43
95.4 26
94.8 0.9
46
94.5 25
96.5
0.7
Office central aortic systolic pressure (mmHg)
43 132.8 26 134.9
0.7
46 131.4 25 138.2
0.3
ABPM systolic BP (mmHg)
43 145.8 26 150.1
0.6
46 144.4 25 154.2
0.2
ABPM diastolic BP, mmHg
43
97.7 26
97.3 0.9
46
96.7 25
99.6
0.5
ABPM peripheral pulse pressure (mmHg)
43
48.0 26
52.8 0.2
46
39.7 25
46.0
0.1
ABPM central aortic systolic pressure (mmHg)
43 137.6 26 141.8
0.6
46 136.3 25 145.6
0.2
ABPM central aortic systolic/systolic pressure ratio
43
0.9 26
0.9 0.2
46
0.9 25
0.9 0.4
Nocturnal systolic dipping (%)
37
6.2 25
4.0 0.1
40
5.8 24
4.5 0.3
Left ventricular mass index (g/m
2
)
42 179.7 26 187.1
0.7
45 188.0 25 198.0
0.8
LVH on echocardiography (%)
43
81.4 27
92.6 0.2
47
85.1 26
88.5
0.7
CAC
–
, coronary artery calcium score
=
0; CAC
++
, coronary artery calcium score
= ≥
1; AAC
–
, abdominal aortic calcium score
=
0; AAC
++
, abdominal aortic
calcium score
= ≥
1; m:f
=
male:female; ABPM, ambulatory blood pressure monitoring; BP, blood pressure.
250
200
150
100
50
50
100
150
200
250
Office systolic blood pressure
Ambulatory systolic blood pressure
Fig. 1.
Correlation between office and ambulatory systolic
blood pressures.
