CARDIOVASCULAR JOURNAL OF AFRICA • Vol 22, No 6, November/December 2011
298
AFRICA
which are about 5 km apart, assisted by senior medical officers
and postgraduate resident doctors and well as nurses. Facilities
available for cardiac evaluation include chest radiography,
12-lead electrocardiography (ECG), exercise ECG, Holter ECG,
ambulatory blood pressure-monitoring devices, spirometry and
echocardiography (ECHO).
This was a cross-sectional study, conducted within a three-
year period. Hypertensive patients were eligible for the study if
they fulfilled the following criteria: (1) no evidence of valvular
abnormality. This was based on clinical examination and absence
of features of valvular heart disease at echocardiography; (2)
absence of congestive heart failure based on previous history of
admission for heart failure or symptoms and signs of heart fail-
ure in the past or at the time of evaluation, using the Framingham
criteria; (3) absence of sickle cell disease based on self-report-
ed haemoglobin electrophoretic pattern of the subject and/or
absence of stigmata of the disease; (4) absence of self-reported
history of renal failure or serum creatinine
≥
2 mg/dl; (5) absence
of ischaemic heart disease based on history, as well as absence of
ischaemic ECG changes at the time of the study (other than left
ventricular hypertrophy with strain pattern); (6) other exclusion
criteria included morbid obesity, pulmonary heart disease (cor
pulmonale), chest abnormality that obscured echo-window and
left bundle branch block pattern on the 12-lead ECG.
Using a simple questionnaire, a nurse screened the patients
for history or symptoms of these and history of previous hospital
admissions relating to the exclusion criteria. All the echocardiog-
raphy request forms were also assessed for evidence of exclusion
criteria. Fig. 1 shows how the patients were selected for final
analysis. Both treated and untreated hypertensive subjects were
recruited. Hypertension was defined according to international
criteria.
10
Baseline clinical and demographic characteristics were
obtained from the subjects. These included date of birth, age,
gender and history of diabetes. Blood pressure measurements
were obtained according to standard guidelines,
11
with a mercury
sphygmomanometer (Accosson London). Systolic and diastolic
blood pressures were measured at Korotkoff sounds phases I and
V, respectively. Blood pressure was measured three times on the
right arm, after a five-minute rest, and averaged. Subjects were
weighed without shoes and in light clothing on a standard beam
balance. Height was measured to the nearest centimetre using an
anthropometrical plane with the subjects without shoes or head-
gear. Body mass index (BMI) was calculated using the formula:
BMI
=
weight (kg)/height (m)
2
. Body surface area (BSA) was
calculated using the formula of Dubois.
12
M-mode, two-dimensional (2-D) and Doppler echocardiogra-
phy were performed using a standard protocol and an ALOKA
SSD 4000 echocardiography machine (Aloka Co, Ltd, Tokyo,
Japan). Two-dimensional guided M-mode measurements were
made according to the recommendations of the American
Society of Echocardiography (ASE).
13
Left ventricular internal
dimension, posterior wall thickness and interventricular septal
thickness were measured at end-diastole and end-systole. Where
optimal M-mode imaging could not be obtained, 2-D linear
measurements were obtained according to the ASE criteria.
13
Left atrial end-systolic diameter was obtained from the trail-
ing edge of the posterior aortic–anterior left atrial complex.
Measurements were obtained in up to three cardiac cycles,
according to the ASE convention.
13
One experienced cardiologist performed all the echocardiog-
raphy. In our laboratory, the intra-observer concordance correla-
tion coefficient and measurement error have been reported.
14
Left ventricular systolic performance (LVSP) was assessed
using the fractional shortening of the left ventricle and the
ejection fraction. Left ventricular ejection fraction (LVEF) was
calculated using the Teichholz formula.
15
Fractional shortening
was calculated from LV internal dimensions in diastole and
systole:
Fractional shortening
=
LVIDd – LVIDs
LVID
×
100
Left ventricular mass (LVM) was calculated using the formula
of Devereux and Reichek.
16
This has been shown to yield LVM
closely related to autopsy measurements (
r
=
0.90)
17
and it had
good inter-observer reproducibility (
p
=
0.93) in one study.
18
Relative wall thickness (RWT) was derived from 2
×
posterior
wall thickness/LV internal diameter.
Left ventricular hypertrophy (LVH) was defined by LV
mass indexed by allometric signal (height
2.7
)
>
51 g/m
2.7
.
19
This
partition value of 51 g/m
2.7
was used since this was the only
criterion that demonstrated as the optimal threshold value for
left ventricular hypertrophy in blacks, irrespective of gender,
in two previous studies. Left ventricular systolic function was
categorised as follows:
20
normal LV function, EF
≥
50%; mild
LVSD, EF 40–49%; moderate LVSD, EF 30–39%; and severe
LVSD, EF
<
30%.
Statistical analysis
SPSS version 11.0 software (SPSS, Chicago, IL, USA) was used
in the analysis of the data. Continuous variables were expressed
as mean
±
SD, while categorical variables were expressed as
counts (percentages). Comparison between the two groups was
assessed with the Student’s
t
-test for independent variables, while
the
χ
2
analysis was used to compare proportions. Analysis of
variance (ANOVA) with Scheffe’s
post hoc
test was used for the
comparison of multiple groups. A two-tailed
p
-value of 0.05 was
assumed statistically significant.
Results
A total of 832 subjects, 415 men (49.9%) and 417 women
(50.1%) were eligible for analysis. Fig. 1 shows the criteria for
selection of subjects for analysis.
The overall mean age of the population was 56.0
±
12.7 years
(range 15–88). Fig. 2 is a histogram showing the age distribu-
Fig. 1. Criteria for selection of the subjects for analysis.
1406 individuals were
referred for evaluation
of their LV function or
assessment for presence
of LVH
832 subjects (417
women and 415 men
eligible for final analysis
546 subjects with
hypertensive heart failure
or symptoms of heart
failure and 28 individuals
with imcomplete data
were excluded
