CARDIOVASCULAR JOURNAL OF AFRICA • Vol 23, No 9, October 2012
AFRICA
479
(
RWT)] has identified four different geometric patterns of LV
adaptation to hypertension.
5
These are concentric LV hypertrophy
(
CH) (increased mass and relative wall thickness), eccentric
hypertrophy(EH)(increasedmass,normalrelativewallthickness),
concentric remodelling (CR) (increased relative wall thickness
with normal mass) and normal LV geometry (NR) (see Fig. 1).
5
Concentric hypertrophy is associated with especially high
arterial pressure while eccentric hypertrophy is associated with
obesity and elevated volume load.
5
A long-term follow-up study
has revealed that those with CH had the highest rates of all-cause
mortality and cardiovascular morbid events, while patients with
EH or CR had rates of morbidity that fell between those of patients
with CH and the low-risk group with normal LV geometry.
6
Although studies have shown that assessing the right and left
ventricles are important in prognostication, and that hypertensive
LV geometric patterns are different from each other in several
respects, as mentioned above,
1-6
it has not previously been well
described whether RV function in subjects with the various LV
geometric patterns are also different. The aims of the present
study were therefore to assess the prevalence, determinants
and correlates of RV systolic and diastolic dysfunction (RVSD
and RVDD, respectively) in a hypertensive population, grouped
according to the various LVgeometric patterns. It is hoped that this
information would further characterise the structure and function
of both the right and left ventricles in hypertensive subjects.
Methods
The study was carried out in the echocardiography laboratory of
Aminu Kano Teaching Hospital in Kano, north-western Nigeria.
The Research Ethics Committee of the Hospital reviewed and
approved the study protocol, which conformed to the ethical
guidelines of the Declaration of Helsinki, on the principles for
medical research involving human subjects.
7
The study was cross-sectional in design. Hypertensive
subjects referred for echocardiography to Aminu Kano Teaching
Hospital, Kano, Nigeria, were recruited consecutively from
October 2009 to April 2010, after obtaining informed consent.
Minimum sample size was estimated at 94 subjects using a
validated formula,
8
applying a prevalence of hypertensive heart
disease (HHD) in Kano of 56.7% (among patients referred for
echocardiography),
9
and a sample error of 10%.
Transthoracic echocardiography was performed by the
authors using the Aloka Cardiac Ultrasound System (model SSD
4000
PHD), and the procedures were carried out according to the
recommendations of theAmericanSocietyof Echocardiography.
10
Left ventricular ejection fraction (LVEF) was calculated using
Teicholz’s M-mode formula while LV mass index (LVMI) was
calculated using Devereux’s formula.
11,12
Patients were examined
in the left lateral decubitus position.
Tricuspid annular plane systolic excursion (TAPSE) was
recorded from the apical four-chamber view with the M-mode
cursor positioned at the free-wall angle of the tricuspid valve
annulus.
13
Right ventricular long-axis excursion amplitude (i.e.
TAPSE) was taken from end-systole to end-diastole.
13
Tracings
for TAPSE and TDI of the RV lateral tricuspid annulus were
obtained from the apical approach during held end-expiration.
Care was taken to align M-mode or TDI beam along the direction
of tricuspid annulus motion. TDI sample volume was positioned
10
mm from the insertion site of the tricuspid leaflets or 10
mm away within the right ventricle lateral wall and adjusted to
cover the longitudinal excursion of the tricuspid annulus in both
systole and diastole.
14
All the recruited subjects were hypertensive on treatment and
in sinus rhythm. Subjects with other conditions that could cause
LV hypertrophy (LVH) or myocardial disease, such as ischemic
heart disease (IHD), valvular heart disease and cor pulmonale
were all excluded. IHD was defined by the presence of any of
the following: history of angina or IHD, electrocardiographic
changes suggestive of myocardial infarction, and regional wall
motion abnormalities on echocardiography. None of the subjects
had a history of any form of cardiac surgery.
Hypertension was defined as systolic blood pressure (SBP)
≥
140
mmHg and/or diastolic blood pressure (DBP)
≥
90
mmHg, according to standard recommendations by the World
Health Organisation.
15
Hypertensive LV geometric patterns were
defined as above and illustrated in Fig. 1.
5
RWT was calculated
using the following formula:
RWT
=
2 (
LV posterior wall thickness at end-diastole) (in mm)
LV end-diastolic dimension (in mm)
.
2
Normal RWT was defined as values
≤
0.42,
and was increased if
RWT was
>
0.42.
Increased LV mass index (LVMI) was defined
as values
>
125
g/m
2
for all subjects.
5
Proximal RV outflow tract
dimension at end-diastole (RVOTd) was used as the measure for
right ventricle size.
13,16
RVSD was defined as either TAPSE of
<
16
mm, or peak
velocity of
<
10
cm/s of the systolic wave (S
m
)
in tissue Doppler
imaging (TDI) of the RV lateral tricuspid annulus, or both.
17
RVDD was defined as the ratio of
<
1.0
of peak velocities of
the early (E
m
)
to late (A
m
)
diastolic waves in the TDI of the RV
lateral tricuspid annulus, which was reported to represent global
RV diastolic function.
2
Pulmonary artery systolic pressure (PASP) was estimated
using continuous-wave Doppler echocardiography, which was
used tomeasure themaximumvelocity of the tricuspid regurgitant
jet (v), with which the trans-tricuspid pressure gradient was
calculated using the modified Bernoulli equation (4v
2
).
18
RV
systolic pressure (RVSP) was then estimated by adding the trans-
tricuspid pressure gradient to the right atrial pressure (RAP).
18
RVSP was then equated to the PASP, given that pulmonary
valve stenosis was excluded.
18
RAP was then estimated using
the diameter and collapse of the inferior vena cava (IVC) during
spontaneous respiration, as previously described.
19
Subjects in the NG group were used as controls to compare
with the others who had abnormal LV geometric patterns.
Data were analysed with SPSS version 16.0. Means and
standard deviations were computed and presented for quantitative
variables. Student’s
t
-
test, Fisher’s exact and Chi-square (
χ
2
)
tests
were used for comparison between groups, as appropriate.
Univariate regression and binary logistic regression models, and
Pearson’s correlation (
r
)
coefficient were used to analyse the
associations between indices for RVSD and RVDD and a number
of variables. Results for regression models were expressed in
odds ratios (OR) and 95% confidence intervals (95% CI). A
p
-
value
<
0.05
was regarded as significant.
Results
A total of 128 subjects were serially recruited, and the results for
RV function and clinical characteristics are presented in Table 1.
