Cardiovascular Journal of Africa: Vol 27 No 1 (January/February 2016)

CARDIOVASCULAR JOURNAL OF AFRICA • Volume 27, No 1, January/February 2016

AFRICA

Methods

This was a cross-sectional, case–control study of the cohort

of children with sickle cell anaemia attending the paediatric

haematology clinic of Wesley Guild Hospital, Ilesa Unit,

Obafemi Awolowo University Teaching Hospital, Ile-Ife. Cases

were consecutive children with SCA (confirmed by haemoglobin

electrophoresis) aged two to 15 years in steady state. The age

limits were set at 15 and two years, as the older children are

managed in our hospital in the adult haematology clinic, and

those younger than two would not be old enough to cooperate

during electrocardiography.

Steady state was defined as a period without any acute

event such as pain, fever, infection or severe anaemia, and no

transfusion in the four weeks preceding recruitment.

Controls

were age- and gender-matched apparently healthy haemoglobin

AA children who attended the children’s welfare clinic of the

hospital for pre-school-entry medical tests. Children with SCA

on hydroxyurea, or those with known congenital or acquired

heart disease, as well as controls with any acute illness in the

previous two weeks were not incuded in the study. Also, none

of the subjects were on medications known to prolong QT

interval, such as halofantrine and anti-histamine. Parents of all

participants agreed to and signed written, informed consents

before commencing the study.

Data on sociodemographic characteristics (age, gender, socio-

economic class) and age at diagnosis were obtained by structured

questionnaires. Socio-economic class was determined using the

occupation of the father and the highest academic qualification

of the mother, as described by Olusanya

et al

Severity of SCD

was assessed using frequency of significant painful episodes,

blood transfusions and SCD-related hospitalisation in the

previous 12 months, and history of complications.

The children’s weights (kg) were measured using the SECA

electronic scale with an accuracy of 0.1 kg, with subjects standing

upright, barefoot and wearing only light clothing. Heights (cm)

were measured with a fixed stadiometer, Spirit Height

, with the

children standing erect and barefoot. From the measured values

of weight and height, the body mass index (BMI) was calculated

(kg/m

Liver and splenic enlargement were assessed clinically and

documented as size (cm), palpable from the corresponding

costal margins, vertically along the mid-clavicular line, using an

inelastic tape measure.

Blood pressures (BP) were taken supine

using the Accuson

mercurial sphygmomanometer. The average

of two readings was documented in mmHg. The systolic BP

corresponded to the first Korotkoff sound while the diastolic BP

corresponded to the fifth Korotkoff sound.

The lipid profiles were determined using CardioMetabolic

Profile 1 test kits to obtain total cholesterol (TC), HDL-C and

triglyceride (TG) levels. Low-density lipoprotein cholesterol

(LDL-C) levels were calculated using the Friedwald equation.

Haematocrit, platelet and total leucocyte counts, serum bilirubin,

creatinine levels, total protein, albumin, aspartate transferase

(AST), alanine transferase (ALT) and alkaline phosphatase

assays were done for the cases using standard methods.

All the participants were evaluated with 12-lead

electrocardiography, which was performed using the Biocare

IE-12A model digital electrocardiography machine at a paper

speed of 25 mm/s and standardised at 0.1 mV/mm. One of the

authors (JAOO) performed and analysed all electrocardiograms.

Measurements of the heart rate, cardiac axis, PR interval, QRS

duration and QT

interval were done in the standard fashion, as

previously described.

16,17

Electrocardiographic reference values

for Nigerian children were used as cut-off values for the duration

of electrocardiographic deflections and intervals.

Sokolow and

Lyon voltage criteria was used to determine LVH on ECG.

Statistical analysis

The clinical, laboratory and ECG profiles of cases and controls

were summarised and presented as proportions and percentages

for categorical data and means

standard deviation (SD), and

median and range for continuous data. Categorical variables

were compared using the chi-squared or Fisher’s exact tests,

while metric data were compared with the independent samples

-test, analysis of variance (ANOVA) or Pearson/Spearman

correlation test as indicated;

-values

0.05 were taken as

statistically significant.

Results

A total of 102 children, comprising 62 homozygous SS cases

and 40 age- and gender-matched haemoglobin AA controls, were

recruited for this study. The overall male:female ratio was 1.4:1.

Their ages ranged from two to 15 years, with a mean

SD of

7.76

3.66 years.

The sociodemographic characteristics and anthropometric

measurements of the cases and controls were similar (Table 1).

However, the cases had lower mean diastolic blood pressure and

mean arterial pressure than the controls (

0.05) (Table 2).

While the mean total cholesterol and LDL-C levels were

significantly lower among the cases than the controls, the mean

triglyceride level was significantly higher among the cases (

0.001). The mean HDL-C value was however comparable

between the two groups (

0.858). Total cholesterol:HDL-C

ratio was also lower among the cases (

0.029) (Table 1).

Table 2 shows the comparison of age-dependent ECG indices

between the cases and controls. The mean ECG-generated heart

rate (HR), PR interval, QRS duration and corrected QT interval

were higher among children with SCA than the controls (

0.05). The average RV5 voltage and combined RV5 and SV1

voltages were also higher among the cases (

0.05), however,

the mean QRS axis was lower, while the mean QT intervals were

comparable between the two groups.

ECG abnormalities: left ventricular hypertrophy (71.0 vs

27.5%), first-degree atrio-ventricular block (19.4 vs 0%) and

T-wave abnormalities consistent with lateral ischaemia (12.9 vs

0%) were significantly more prevalent among cases than controls

(

0.000, 0.008 and 0.021, respectively). Also, children with

SCA were about six times more likely to have LVH than age-

and gender-matched haemoglobin AA children (OR

6.4, 95%

2.7–15.6). None of the study participants had left atrial

enlargement or T-wave inversion.

There was no statistical difference in the frequency of

occurrence of tall T-wave abnormalities, sinus rhythm with

ventricular premature complex, right atrial enlargement, right

or biventricular hypertrophy, ST depression and conduction

anormalies, such as right ventricular conduction delay and

non-specific intraventricular conduction block between the

two groups. On the other hand, abnormal left-axis deviation