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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 27, No 1, January/February 2016
18
AFRICA
and ST-segment elevation were non-significantly less prevalent
among children with SCA compared to the controls (Table 3).
In all, only 13 (21.0%) of the cases against 22 (55.0%) of the
controls had no identifiable ECG abnormalities (
p
=
0.000, OR
=
4.6, 95% CI
=
1.9–10.9). Those with identifiable abnormalities
included about half; 30 (48.4%) with multiple abnormal ECG
features and 19 (30.6%) with single abnormal ECG reports. There
was no significant correlation between some ECG durations
(heart rate, PR, QRS, QT
C
and QT intervals) and frequency
of significant pain episodes, SCD-related hospitalisation or
transfusion in the 12 months preceeding the study (
p
> 0.05) in
each occasion.
Haematocrit level had a negative correlation with QT
C
interval (
r
=
–0.3,
p
=
0.016) and QT intervals (
r
=
–0.3,
p
=
0.044). While liver enzyme AST levels had a moderate positive
correlation with heart rate (
r
=
0.5,
p
=
0.025), ALT levels had
a negative correlation with heart rate (
r
=
–0.3,
p
=
0.000) and
PR interval (
r
=
–0.3,
p
=
0.015). Albumin values were positively
correlated with QRS interval (
r
=
0.5,
p
=
0.013), and triglyceride
levels positively correlated with PR interval (
r
=
0.3,
p
=
0.012).
Leucocyte and platelet counts, serum total, direct and indirect
bilirubin, alkaline phosphatase, total protein, total cholesterol,
HDL-C and LDL-C levels had no significant correlation with
heart rate, PR, QRS, QT and QT
C
intervals in children with SCA.
There were no significant statistical differences in the
sociodemographic and clinical characteristics of SCA children
with or without ECG abnormalities (Table 4). However, the
mean values of triglycerides and serum ALT of SCA children
with ECG abnormalities were significantly higher than those
with normal ECG patterns (
p
=
0.007 and 0.045, respectively)
(Table 5).
Table 1. Baseline characteristics of the cases and controls
Baseline characteristics
Cases
(n
=
62)
Controls
(n
=
40) p-value 95% CI
Male gender
39 (62.9)
21 (52.5)
0.297 0.7–3.4
Age (years), mean
±
SD 7.77
±
3.87 7.75
±
3.35 0.974 1.4–1.5
Median age (range)
7.0 (2–16)
8.0 (2–14)
Age 2–5 years,
n
(%)
18 (29.0)
13 (32.5)
Age 6–10 years,
n
(%)
31 (50.0)
18 (45.0)
0.883 NA
Age
>
10 years,
n
(%)
13 (21.0)
9 (22.5)
Upper class,
n
(%)
18 (29.0)
16 (40.0)
Middle class,
n
(%)
19 (30.6)
11 (27.5)
0.507 NA
Lower class,
n
(%)
25 (40.3)
13 (32.5)
Weight (kg), mean
±
SD 22.90
±
7.76 26.36
±
10.85 0.084 –7.4–0.5
Height (m), mean
±
SD 1.21
±
0.20 1.26
±
0.21 0.313 –0.1–0.04
Pulse pressure (mmHg)
35.97
±
8.68 30.75
±
7.56 0.191 –1.6–1.3
Total cholesterol (mmol/l) 2.60
±
0.42 3.11
±
0.41 0.000 0.3–0.8
HDL-C (mmol/l)
0.96
±
0.36 0.95
±
0.35 0.858 0.1–0.6
Triglycerides (mmol/l)
1.59
±
0.62 0.99
±
0.45 0.000 1.4–1.9
LDL-C (mmol/l)
1.27
±
0.60 1.69
±
0.48 0.000 0.2–0.6
Total cholesterol:HDL-C 3.11
±
1.44 3.80
±
1.60 0.029 1.3–1.7
HDL-C
=
high-density lipoprotein cholesterol; LDL-C
=
low-density lipo-
protein cholesterol; CI
=
confidence interval; NA
=
not applicable.
Table 2. Comparison of age-dependent mean electrocardiographic indices and blood pressure parameters between cases and controls
ECG and BP parameters
2–5 years
6–10 years
11–15 years
Cases mean (SD) Controls mean (SD) Cases mean (SD) Controls mean (SD) Cases mean (SD) Controls mean (SD)
HR (beats/min)
109.8 (9.0)
95.6 (13.1)
b
95.0 (9.6)
90.4 (1.0)
b
85.4 (1.5)
80.1 (5.1)
b
PR interval (ms)
141.1 (8.1)
135.9 (1.2)
b
156.4 (19.3)
142.7 (14.8)
b
161.7 (30.9)
136.9 (15.7)
b
QRS interval (ms)
77.2 (8.6)
72.1 (0.4)
b
86.4 (16.9)
75.2 (5.9)
b
89.5 (3.5)
81.9 (8.7)
b
QT interval (ms)
333.2 (16.7)
334.4 (28.2)
a
355.5 (18.9)
345.2 (20.5)
a
376.5 (31.2)
360.3 (13.5)
a
QT
C
interval (ms)
449.6 (13.4)
421.9 (32.5)
b
445.4 (16.6)
415.4 (20.3)
b
451.9 (23.4)
415.7 (14.5)
b
P axis (°)
42.8 (12.3)
42.4 (19.4)
a
34.2 (18.9)
41.4 (11.7)
a
39.5 (22.0)
41.6 (13.2)
a
QRS axis (°)
43.8 (17.3)
58.0 (22.1)
a
38.8 (21.6)
54.7 (20.0)
b
47.9 (14.5)
53.3 (24.9)
a
T axis (°)
41.2 (13.4)
43.1 (16.7)
a
38.9 (17.8)
47.7 (11.7)
a
54.8 (50.5)
42.3 (16.5)
a
RV5 voltage (mV)
3.1 (1.0)
2.1 (0.9)
b
3.8 (0.8)
2.5 (0.6)
b
3.7 (0.9)
2.8 (0.4)
b
SV1 voltage (mV)
1.7 (0.7)
1.9 (0.6)
a
1.8 (0.6)
1.4 (0.8)
a
1.7 (0.4)
1.4 (0.3)
a
RV5 + SV1 voltage (mV)
4.8 (1.3)
4.0 (0.2)
b
5.6 (0.8)
3.9 (0.9)
b
5.4 (1.1)
3.9 (1.4)
b
SBP (mmHg)
76.4 (11.0)
82.3 (12.2)
a
89.0 (10.0)
83.3 (13.5)
a
94.6 (9.9)
95.0 (7.1)
a
DBP (mmHg)
43.6 (9.0)
54.2 (7.3)
b
46.3 (8.7)
55.8 (8.9)
b
52.6 (7.9)
60.0 (7.1)
b
MAP (mmHg)
54.5 (8.9)
63.6 (8.6)
b
60.5 (0.3)
65.0 (1.9)
b
66.6 (1.7)
71.7 (6.7)
b
SBP
=
systolic blood pressure; DBP
=
diastolic blood pressure; MAP
=
mean arterial pressure;
a
No significant difference between cases and controls (
p
>
0.05);
b
Significant difference between cases and controls (
p
<
0.05).
Table 3. Prevalence of ECG abnormalities among children with SCA
and age- and gender-matched haemoglobin AA controls
ECG abnormalities
Cases
n (%)
Controls
n (%) p-value
Odds ratio
(95% CI)
Sinus arrhythmia
5 (8.1) 4 (10.0) 0.737 0.8 (0.2–3.1)
Sinus rhythm with ventricular
premature complex
1 (1.6)
0 (0)
1.000 2.0 (0.1–47.9)
Right atrial enlargement
3 (4.8)
0 (0)
0.417 1.7 (1.4–2.0)
Left ventricular hypertrophy 44 (71.0) 11 (27.5) 0.000 6.4 (2.7–15.6)
Right ventricular hypertrophy 5 (8.1)
1 (2.5)
0.462 3.4 (0.4–30.4)
Biventricular hypertrophy
3 (4.8)
0 (0)
0.158 1.7 (1.4–2.0)
ST-segment elevation
3 (4.8)
3 (7.5)
0.899 0.6 (0.1–3.2)
ST depression
4 (6.5)
0 (0)
0.264 1.7 (1.4–2.0)
Tall T-wave anomaly
1 (1.6)
0 (0)
1.000 1.9 (0.1–47.9)
T-wave abnormality consistent
with lateral ischaemia
8 (12.9)
0 (0)
0.021 12.6 (1.7–21.7)
Non-specific T-wave
abnormalities
4 (6.5)
1 (2.5)
0.646 2.7 (0.3–24.3)
Right ventricular conduction
delay
1 (1.6)
0 (0)
1.000 2.0 (0.1–47.9)
Non-specific intraventricular
conduction block
2 (3.2)
0 (0)
0.519 3.4 (0.2–69.1)
Abnormal left-axis deviation 1 (1.6)
2 (5.0)
0.559 0.3 (0.1–3.5)
First-degree atrio-ventricular
block
12 (19.4)
0 (0)
0.008 1.8 (1.5–2.2)
Presence of at least one
abnormality on ECG findings
49 (79.0) 18 (45.0) 0.000 4.6 (1.9–10.9)