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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 27, No 1, January/February 2016
AFRICA
39
with this approach. RV-FAC was determined by means of the
formula:
RV-FAC
=
end-diastole area – end-systole area
____________________________
end-diastole area
Tricuspid annular plane systolic excursion (TAPSE) was
calculated by measuring the movement magnitude of the RV
annular segment in the longitudinal plane using the M-mode
method. This measurement was performed on the apical four-
imaging window of the tricuspid lateral annulus.
Right ventricle isovolumic acceleration (RV-IVA) was
calculated by dividing the peak isovolumic myocardial velocity
calculated at the time of isovolumic contraction by the time
to peak velocity using tissue Doppler on the lateral tricuspid
annulus. RV-S
′
was calculated by measuring systolic velocity
using tissue Doppler on the right ventricular lateral tricuspid
annulus.
Right ventricle myocardial performance index (RV-MPI) is
one of the methods recommended for the evaluation of global
RV function. It was calculated by dividing the sum of isovolumic
contraction time (IVCT) and isovolumic relaxation time (IVRT)
by the tricuspid ejection time:
13-17
RV-MPI
=
IVRT + IVCT
____________
ET
Left ventricular ejection fraction (LVEF) was calculated from
the four- and two-chamber views using the modified Simpson
biplane method. LV wall-motion score index (LV-WMSI) was
calculated according to the 16-segment model of the American
Society of Echocardiography. In accordance with this model,
normokinesis, mild-moderate hypokinesis, severe hypokinesis,
akinesia and dyskinesia were evaluated with the scores 1, 2, 3, 4
and 5, respectively. The total value was divided into the evaluated
segment number and WMSI was obtained.
18
Echocardiographic examinations were performed by the same
investigators, who were blinded to the patients’ data, at baseline
and after the first month. All measurements were calculated
from three consecutive cycles, and the average of the three
measurements was recorded.
Speckle-tracking echocardiography
Two-dimensional speckle-tracking echocardiography (2D STE)
is a novel technique used for the measurement of cardiac
mechanics. It assessesmyocardial deformation and themyocardial
deformation rate by tracking speckles in the myocardium on
grayscale (B-mode) images, and can be used to evaluate both
global and regional myocardial strain and strain rate.
19,20
The investigations were performed with the patients in the
left lateral decubitus position, in the parasternal and apical
four-chamber views. Digital routine grayscale 2D ciné loops and
tissue Doppler ciné loops were obtained from three consecutive
beats with end-expiratory apnoea from standard apical four-
and two-chamber views. Frame rates of 70–90 Hz were used
for routine grayscale imaging in the speckle-tracking analysis.
Sector width was optimised to allow for complete myocardial
visualisation while maximising the frame rate. Gain settings were
adjusted for routine clinical grayscale 2D imaging to optimise
endocardial definition.
Longitudinal deformation in the RV free wall was assessed
by 2D speckle-tracking longitudinal strain using a routine
grayscale RV focused-view image, which was performed offline
with dedicated software (EchoPAC 108.1.12, General Electric-
Vingmed Medical Systems, Horten, Norway) by one experienced
cardiologist blinded to data about the patients’ status.
Briefly, a region of interest (ROI) was traced with a point-
and-click approach on the endocardium at end-diastole in the
RV from the RV focused view. A second, larger ROI was then
generated and manually adjusted near the epicardium. The RV
was divided into six standard segments (at the basal, middle and
apical levels), and six corresponding time–strain curves were
generated. RV free-wall longitudinal speckle-tracking strain
(RV-free-S) was calculated by averaging each of the three
regional peak systolic strains along the entire RV free wall and
RV free systolic strain rate (RV-free-SR), were calculated in the
same manner.
The patients were prospectively followed during the in-hospital
period and first month after RV-STEMI. Informed consent was
obtained from each subject, and the study was conducted in
accordance with the Helsinki Declaration. The study protocol
was approved by the ethics committee.
Variability analysis
Intra- and inter-observer variability were assessed in the echo-
cardiographic data obtained from a subgroup of 30 subjects.
One month later, the first operator repeated the analysis to assess
intra-observer variability. To assess inter-observer variability, the
second operator who was unaware of the previous measurements,
analysed the rotational parameters two days later.
Agreement analysis for inter- and intra-observer variability
of RV measurements revealed a high level of agreement, with a
mean difference of 0.18 (95% limit of agreement –0.5, 0.96). For
intra-observer variabilities, intraclass correlation coefficient of
RV-free-ST and RV-free-STR-S were 0.907 (95% CI 0.840–0.943)
and 0.954 (95% CI 0.823–0.967), respectively.
Statistical analysis
SPSS 17 (SPSS Inc, Chicago, IL, USA) was used for statistical
analysis. The Kolmogorov–Smirnov test was used to evaluate
whether the numerical variables were normally distributed. For
data showing an abnormal distribution, median and interquartile
ranges were displayed. Continuous variables were presented as
mean
±
standard deviation, and categorical ones were presented
as percentage (%).
The two study groups were compared using the Student’s
t
-test or Mann–Whitney U- and chi-squared or Fisher’s exact
tests, as appropriate. In each group, follow-up comparisons
(early period and one month) were performed using the paired
t
-test and Wilcoxon rank test, as appropriate. Intraclass
correlation coefficients and Bland–Altman analysis were used
for echocardiographic measurements to assess intra- and inter-
observer reproducibility, respectively. A
p
-value
<
0.05 was
considered statistically significant.
Results
There were 172 male patients in the study and the mean age was
63.7
±
11.8 years. One-month clinical follow up was available