CARDIOVASCULAR JOURNAL OF AFRICA • Vol 23, No 5, June 2012
256
AFRICA
guidelines.
17
Systolic and diastolic blood pressure was measured
at Korotokoff sound phases 1 and V, respectively. Subjects with
blood pressure higher than 140/90 mm/Hg and body mass
index (BMI) above 25 kg/m
2
were excluded from the study.
Other exclusion criteria were existing heart disease and diabetes
mellitus.
Echocardiographic examination was performed with the
subjects in partial left lateral decubitus position using an Aloka
SSD1700 machine (Aloka Co. Ltd, Tokyo, Japan) with a 3.5-MHz
transducer. Two-dimensional guided M-mode measurements
were obtained as recommended by the American Society of
Echocardiography.
18
Left ventricular (LV), septal, posterior wall
thickness and cavity dimensions were measured using leading-
edge methodology at both end-diastole and end-systole. Left
ventricular mass (LVM) was calculated using the formula of
Devereux and Reichek.
19
This has been shown to yield LVM
closely related to autopsy measurements (
r
=
0.90),
20
and had
good inter-observer reproducibility (
p
= 0.93) in one study.
21
LVM was indexed by the allometric power of height (LVM/
Ht
2.7
).
22
Left ventricular hypertrophy was considered present if
the left ventricular mass index (LVMI) was
≥
46 g/m
2.7
. Relative
wall thickness (RWT) was calculated as 2RWTd/LVIDd (left
ventricular internal diameter).
7
Increased wall thickness was
present when RWT
>
0.45.
23
Ejection fraction was calculated
using the formula of Teichholz.
24
Doppler echocardiography was used for transmitral flow
velocities, obtained with the Doppler sample volume placed
just beyond the tip of the mitral valve leaflets. The parameters
measured were early diastolic peak flow velocity (E), early
diastolic flow time (EDFT), late diastolic peak flow velocity (A),
late diastolic flow time (ADFT), the deceleration time of early
mitral velocity, and the ratio of E to A (E/A).
Isovolumic relaxation time (IVRT) was measured with the
pulse-wave Doppler beam intersecting the LV outflow and inflow
tracts. EDFT was measured from the onset of diastolic flow to
the intersection of a line extrapolated to the baseline, and ADFT
was measured from the onset of late diastolic flow to the end of
diastolic flow.
25
Pulmonary venous flow recordings were obtained from a
four-chamber view directed at the right upper pulmonary vein.
The sample volume was placed 1–2 cm into the pulmonary
vein and the following measurement were recorded: peak
S-wave velocity (peak systolic pulmonary venous inflow
velocity during ventricular systole), peak D-wave velocity (peak
diastolic pulmonary venous inflow velocity during early phase
of diastole), peak AR-wave velocity (peak reversed systolic
wave during atrial contraction), and duration of the reverse atrial
contraction-induced diastolic flow.
26
Myocardial Doppler velocities were measured in the apical
four-chamber view with the Doppler beam well aligned to
the septum and the pulsed Doppler sample volume placed 1
cm apically from the mitral annulus in the interventricular
septal myocardium. The following measurements were made:
myocardial isovolumic contraction time, myocardial peak
systolic velocity (Sm), myocardial contraction time, myocardial
isovolumetric relaxation time, myocardial early diastolic
relaxation velocity (Em), and myocardial late relaxation velocity
(Am). Other measurements were the duration of the diastolic
period and the durations of Em and Am. Measurements from
three cardiac cycles were taken and averaged.
The calculation of the sample size for this study was based on
a difference of 0.2 in the mitral E/A ratio between the controls
and the subjects, with a 90% power to detect the difference at
a significance level of 0.05 in a two-tailed test. The estimated
sample size was 63 subjects per group. [This was based on
data from a previous study where LVM (
±
SD) in hypertensive
and normotensive offspring was 125 (29) and 109 (25) g,
respectively.]
27
Statistical analysis
All data generated were entered into a standard proforma. SPSS
software, version 10.0 (SPSS Inc., Chicago, Illinois) was used
for statistical analysis. Continuous variables were expressed as
mean (standard deviation). Differences in continuous variables
between the groups were assessed with a
t
-test for independent
groups. Where data were not normal, the Mann-Whitney test
was used to compare the two groups. Data were adjusted for
covariates using analysis of covariance. A two-tailed
p-
value
<
0.05 was considered significant.
Results
Table 1 shows the baseline characteristics of the participants
(subjects and controls). Systolic and diastolic pressure, mean
arterial pressure, age, height and body mass index were
comparable in the two groups.
The cardiac structure and systolic functional data are listed
in Table 2. Apart from the left atrial diameter and septal
wall thickness at systole that was greater in the offspring of
hypertensive subjects, relative LV wall thickness, LVM, LVMI,
aortic root diameter, left atrial diameter, LV internal diameters
and LV ejection fraction were similar in both groups.
Table 3 shows the echocardiographic diastolic functional
indices in both groups. The duration of the E wave and
pulmonary A reversal flow was significantly higher in the
offspring of hypertensive subjects than in the controls. The
deceleration time of the E wave (DT) was lower in offspring of
hypertensive subjects.
Table 4 shows the measured tissue Doppler parameters.
Offspring of hypertensive subjects had a higher myocardial
isovolumetric relaxation time as well as a lower myocardial E
TABLE 1: BASELINE CHARACTERISTICS OF THE SUBJECTS
Characteristics
Offspring of
hypertensive
parents
(
n
=
80)
Offspring of
normotensive
parents
(
n
=
62)
p
-value
Age (years)
25.0 (5.31)
24.3 (3.60)
0.369
Weight (kg)
64.2 (10.87)
63.2 (9.93)
0.565
Height (cm)
1.7 (0.10)
1.7 (0.10)
0.856
Body mass index (kg/m
2
)
22.9 (3.07)
22.6 (2.51)
0.499
Body surface area (m
2
)
1.7 (0.18)
1.7 (0.17)
0.659
Waist circumference (cm)
79.8 (9.12)
77.6 (7.21)
0.177
Hip circumference (cm)
97.2 (8.78)
94.6 (8.85)
0.121
Waist–hip ratio
0.8 (0.05)
0.8 (0.07)
0.838
Systolic blood pressure (mmHg)
115.0 (12.88) 111.7 (10.08) 0.122
Diastolic blood pressure (mmHg)
72.8 (8.57)
70.5 (8.76)
0.131
Pulse pressure (mmHg)
42.2 (11.35)
41.2 (10.19)
0.789
Mean arterial pressure (mmHg)
86.9 (8.70)
84.3 (7.87)
0.067
Heart rate
76.6 (12.90)
76.8 (12.30)
0.909
