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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 31, No 3, May/June 2020
AFRICA
125
Standard two-dimensional, M-mode, pulsed-Doppler and tissue
Doppler echocardiographic examinations were performed with the
S5
®
cardiac ultrasonography system (GE Medical Systems; Horten,
Norway) and a 6-MHz transducer. Simultaneous echocardiographic
recordings were obtained. One echocardiographer (blinded
to the patients’ clinical and laboratory data) interpreted each
echocardiographic examination independently. All the patients were
examined while at rest in the supine position and images were taken
from the third or fourth intercostal space. The measurements were
recorded according to the American Society of Echocardiography
guidelines.
14
Three values were recorded for each examination and
the average of the values was used.
The examination consisted of two-dimensional, M-mode and
pulsed- and continuous-wave Doppler velocities of the cardiac
valves and tissue Doppler imaging (TDI) of the ventricles.
Left ventricular (LV) dimensions, shortening fraction, ejection
fraction, and mitral (MAPSE) and tricuspid annular plane
systolic excursion (TAPSE) were measured using the standard
M-mode technique. TAPSE and MAPSE were measured in an
M-mode examination in the apical four-chamber view during
systole, at the junction of the right and left ventricle with the
tricuspid and mitral valve, and expressed in mm.
Pulsed Doppler measurements were performed with the
transducer from the apical four-chamber view. The LV inflow
pattern at the tips of the mitral valve provided peak early (E)
and late (A) filling velocities and the E/A ratio was determined.
LV and right ventricular (RV) tissue Doppler echocardiographic
evaluations were performed from the apical four-chamber
position by placing the pulsed-wave Doppler beam on the part
of the mitral annulus that was closest to the LV lateral wall and
inter-ventricular septum for the left ventricle, and on the part of
the tricuspid annulus that was closest to the RV lateral wall for
the right ventricle.
Peak systolic (S), early diastolic (E
′
) and late diastolic (A
′
)
myocardial velocities at the basal segments of the lateral mitral
annulus, septal mitral annulus and tricuspid annulus were
determined using TDI. The isovolumetric contraction time
(interval from the end of the A
′
wave to the beginning of the
S
′
wave) and the isovolumetric relaxation time (interval from
the end of the S
′
wave to the beginning of the E
′
wave) were
measured on TDI for the lateral mitral annulus, septal mitral
annulus and tricuspid annulus.
The following formula was used with a view to calculating the
myocardial performance index (MPI):
MPI =
IVCT + IVRT
____________
ET
where IVCT = isovolumetric contraction time, IVRT =
isovolumetric relaxation time and ET = ejection time (defined
as the duration of the S
′
wave). All values used for analysis
represented the average of three consecutive cardiac cycles, with
the exception of patients with dysrhythmia, in whom three-beat
averages were obtained.
M mode of the ascending aorta was obtained above 2–3 cm
from the aortic valve to calculate arterial wall stiffness indices,
and systole (AoS) and diastole (AoD) measurements were
averaged from five consecutive heartbeats. Aortic strain (AS),
aortic distensibility index (DI) and aortic stiffness index (SI)
were calculated from the following formulae:
15
AS (%) =
(AoDS–AoDD)
_____________
AoDD
× 100
SI =
ln(SBPDBP)
________________________
(AoDS–AoDD)/AoDD
DI (cm
2
/dynes × 10
-6
) =
(AoDS–AoDD) × 10
-3
__________________
AoDD/(SBP–DBP)
× 2
where SBP = systolic blood pressure (mmHg), DBP = diastolic
blood pressure (mmHg), AoDS = aortic diameter in systole
(mm), AoDD = aortic diameter in diastole (mm), ln = natural
logarithm.
Statistical analysis
Statistical analyses were performed using the Statistical Package
for Social Sciences (version 24.0, SPSS, Inc). Normally distributed
data are presented as mean and standard deviation (SD), and
non-parametric data are presented as median and ranges. Data
obtained by echocardiography were compared between the
three groups using one-way analysis of variance (ANOVA) or
Kruskal–Wallis tests, depending on the distribution of data.
An overall
p
-value of less than 0.05 was considered to show a
statistically significant result.
Results
The demographic data of the studied population are presented
in Table 1. No significant differences were found between the
groups in terms of age at enrollment, gender, gestational age,
birth weight and weight at enrollment. There were no statistically
significant differences between the patient groups and the control
group in terms of systolic or diastolic blood pressure and heart
rate.
The mean for gestational age (GA) of the patients was found
to be 29.8 ± 2.7 weeks (range 24–35) in the LPC group, 29.3
± 2.9 weeks (24–34) in the IVA group, and 29.5 ± 2.8 weeks
(25–36) in the control group. The mean for birth weight (BW)
of the patients was found to be 1 464 ± 451 g (730–2 500) in
the LPC group, 1 279 ± 320 g (720–1 950) in the IVA group,
and 1 352 ± 394 g (770–2 450) in the control group. The mean
age was 17 ± 4.4 months for the patients in the LPC group,
14.4 ± 4.9 months for the patients in the IVA group, and 14.5 ±
2.8 months for the patients in the control group (Table 1). The
mean echocardiographic evaluation time was 12.9 ± 2.3 months
following the injection of aflibercept, and 13.2 ± 2.8 months
after LPC treatment.
All infants in the groups had favourable anatomical outcomes
after treatment for ROP.
There were no statistically significant differences between the
groups in LV M-mode diameters and function (ejection fraction
and fractional shortening). M-mode measurements are shown in
Table 2. From the Doppler parameters, tricuspid E-wave values
were increased significantly in the treatment groups rather than
in the control group (
p
= 0.037), and in comparison between
the treatment groups, tricuspid E-wave values were increased
significantly in the IVA group (
p
= 0019). Comparison of the
other standard trans-mitral and tricuspid Doppler parameters
yielded similar E wave, A wave and E/A ratio for the three groups
(Table 3). TAPSE measurements were also similar between the
patient and control groups. MAPSE values were reduced in
the treatment groups but not in the control group (
p
= 0.002);
in addition, there were no significant differences between the
treatment groups (
p
= 0.175).