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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 30, No 4, July/August 2019
AFRICA
217
Transthoracic echocardiography was performed on all
patients in the left lateral position by experienced sonographers
using a S5-1 transducer on a Philips iE33 system (Amsterdam,
the Netherlands). The images were obtained according to a
standardised protocol. The data were transferred and analysed
offline using the Xcelera workstation (Philips).
All linear chamber measurements were performed according
to the American Society of Echocardiography (ASE) chamber
guidelines.
14
Measurements relating to LV diastolic function were
performed in accordance with the ASE guidelines on diastolic
function and included pulse-wave Doppler at the mitral tips
and tissue Doppler of both medial and lateral mitral annuli.
15
Measurements relating to the RV were based on the ASE
guidelines on the RV.
16
All LV volumes were indexed to body
surface area. We used a LV ejection fraction (EF) cut-off of
<
60% to define decreased LV systolic function in MR.
17
MR was considered of rheumatic aetiology when the
morphology of the valve satisfied the proposed World Heart
Federation criteria for the diagnosis of chronic rheumatic heart
disease (RHD).
18
MR severity was assessed with an integrated
approach using qualitative, semi-quantitative and quantitative
methods as per ASE valvular regurgitation guidelines.
19
Two-dimensional echocardiography images were obtained
at end-expiration from LV long-axis apical four-, three- and
two-chamber (A4C, A3C and A2C) views with frame rates of
60–80 frames per second.
20
Three consecutive cardiac cycles
were recorded and averaged.
21
LV endocardial surface was traced
manually in the three views by a point-and-click approach.
20,22
The speckle-tracking points were modified to allow for adequate
speckle-tracking of the LV wall.
20,22
The LV was divided into 17
segments. Peak LV longitudinal systolic strain was calculated
for long-axis A4C, A3C and A2C views, and global LV systolic
strain was calculated by averaging the three apical views.
20,22
RV free-wall PSSwas derived fromamodifiedA4CRV focused
view.
10
Once three points, namely the RV apex, medial and lateral
tricuspid annulus, were defined, the software automatically
traced the endocardial and epicardial border.
10
Philips QLAB
version 9.0 software allowed off-line semi-automated analysis
of speckle-based strain. This results in the division of the RV
into six standard segments in the A4C view.
10,23,24
The region of
interest, once created, can be manually adjusted as needed to
allow for adequate speckle-tracking.
6
The RV free-wall PSS was
obtained by averaging three lateral segments (the basal, mid and
apical RV wall).
25
The interventricular septum was excluded from
analysis.
23,24
The longitudinal
ε
curves for each segment and a
mean curve of all segments was generated by the software. These
curves were used to derive peak negative RV free-wall PSS.
Statistical analysis
This was performed with Statistica (version 12.5, series 0414 for
Windows). Continuous variables are expressed as mean
±
SD or
median (IQR). The Student’s
t
-test or Mann–Whitney
U
-test
were used to compare continuous variables. Categorical variables
were evaluated with the chi-squared and Fisher’s exact tests when
necessary. A
p
-value of
<
0.05 was recognised as statistically
significant.
Univariate and multivariate linear regression analysis was
used to identify possible independent determinants of RV free-
wall PSS. The independent variables with
p
≤
0.05 on univariate
analyses were tested in multivariate models. Pearson’s correlation
coefficient was used to assess the co-linearity between variables.
These models were further analysed using the forward and
backward multiple linear regression methods.
The intra- and inter-observer variabilities were assessed
for RV free-wall PSS and LVGLS. Measurements were done
in 20 randomly selected subjects. Inter- and intra-observer
reproducibility was assessed by calculating coefficients of
variation. A
p
-value
<
0.05 was considered statistically significant.
Results
There was no statistically significant difference in age, gender,
systolic blood pressure, diastolic blood pressure, body mass index
and heart rate between the patients with MR and the controls (
p
>
0.05) (Table 1). Hypertension, HIV and a combination of the
two co-morbidities were identified in 41.5, 12.9 and 15.5% of
patients, respectively. Forty-two per cent of the patients were in
New York Heart Association functional class 1, the remainder
were in class 2 (49%) and 3 (9%).
Among the CRMR patients, moderate MR was present in
51 (66%) and severe MR in 26 (34%) subjects. As expected,
compared to controls, linear and volumetric measures of the LV
revealed a greater degree of LV dilatation, and LV mass as well
as left atrial volumes were increased. LVEF was significantly
lower in CRMR patients compared to the controls. In addition,
analysis of LV diastolic parameters revealed that compared to
the controls, E
′
of both annuli was lower and E/E
′
was higher
(Table 2).
Pulmonary artery systolic pressure (PASP) was significantly
higher in the MR group compared to the controls (35.1
±
16.9 vs 22.1
±
5.6 mmHg,
p
<
0.0001). Grade
≥
2+ tricuspid
regurgitation (TR) was present in 30% of the patients with
CRMR. No difference was noted between RV basal size, right
atrial volume indexed, tricuspid annular plane systolic excursion
(TAPSE) and RVS
′
between the CRMR and control groups.
However RV free-wall PSS was significantly lower in the CRMR
patients compared to the controls (Table 2, Fig. 1).
Patients with severe CRMR had higher PASP and a greater
degree of RV hypertrophy compared to those with moderate
MR (Table 3). RV free-wall PSS was significantly lower in
severe MR compared to patients with moderate MR, whereas
no difference was detected between these groups for both
TAPSE and tricuspid S
′
. A similar trend of depressed RVPSS
with unchanged TAPSE and RVS
′
was noted when comparing
patients with LV dysfunction with those with preserved LVEF
(Table 4).
Table 1. Baseline clinical characteristics of the study population
Variable
CRMR patients
(
n
=
77)
Controls
(
n
=
40)
p
-value
Age (years)
44
±
13.6
42
±
13.4
0.4
Gender (M:F)
13:64
8:32
0.6
Body surface area (m
2
)
1.7
±
0.2
1.8
±
0.2
0.01
Body mass index (kg/m
2
)
27.1
±
5.9
28.4
±
6.2
0.3
Systolic blood pressure (mmHg)
124.2
±
11.4
124
±
17.5
0.94
Diastolic blood pressure (mmHg)
77
±
9.1
75.7
±
12.6
0.52
Heart rate (beats/min)
77.1
±
12.6
76.3
±
14.1
0.75
Data are presented as mean
±
SD or %.
CRMR: chronic rheumatic mitral regurgitation.