CARDIOVASCULAR JOURNAL OF AFRICA • Vol 23, No 9, October 2012
AFRICA
485
were taken from three consecutive cycles and the averaged
values were calculated and reported as the main records.
Intra- and inter-observer variability of the measurements
were checked and calculated on a sample of patients by
means of re-measurement of systolic and diastolic velocities
by the same observer (intra-observer variability) and a second
blinded observer (inter-observer variability). The calculated
mean percentage error or disagreement was so low as to
be considered negligible. Pre-stenting values of the Doppler
echocardiographic profile were assumed to represent so-called
‘
significant coarctation’, while post-stenting data corresponded
with ‘no coarctation’.
Definitions
Echocardiographic indices performed were defined as follows:
•
Deceleration time (DT) was measured from peak E velocity to
the point where the slope of the slowing flow would intercept
the baseline.
21
•
Systolic acceleration time was measured from the onset of the
systolic upstroke to the systolic peak.
21
•
Pressure half-time (PHT) was the time interval for the peak
pressure gradient to be reduced by one half (PHT
=
0.29
×
DT).
21
•
Abdominal aortic pulse delay was quantified by measuring
the time to peak velocity in the abdominal aorta and compar-
ing it with the same value measured from flow at the aortic
annulus. This value should be indexed to the heart rate by
dividing the absolute value by the square root of the PR
interval.
21
•
Pulsatility index was the systolic velocity minus diastolic
velocity divided by the mean velocity
[
systolic velocity – diastolic velocity
_____________________
mean velocity
].
22
•
Early diastolic velocity (EDV) was maximum diastolic veloc-
ity in early diastole.
•
Late diastolic velocity (LDV) was maximum diastolic veloc-
ity in late diastole (atrial contraction).
23
•
Peak systolic velocity was maximum systolic velocity.
24
•
Velocity time integral was the area under the velocity curve.
•
Time to peak systolic velocity was the time from onset of the
QRS complex to peak systolic velocity measured by pulse-
wave Doppler echocardiography.
•
Pulse delay index was calculated by means of the following
equation:
Time to peak systolic velocity of LVOT – Time to peak systolic velocity of abdominal aorta
____________________________________________________
√
_________
RRinterval
Statistical analysis
Data were analysed using SPSS v 17 software (Chicago, IL,
USA). For each of the measured variables or indices, descriptive
values were expressed as the mean
±
SD for normally distributed
variables, and median and interquartile range (IQR) in the case
of non-normal distributions. All data were initially analysed
using the Kolmogorov–Smirnov test to assess for normality. The
within-group changes of each Doppler echocardiographic index
were evaluated using the paired
t
-
test. Pearson’s correlation
analysis was also used to assess the relationship between
baseline aortic gradient measured by catheter and Doppler
echocardiographic indices.
Receiver operating characteristic curve (ROC) analysis was
performed to assess the predictability of significant coarctation
(
pre-stenting condition) with the quantitative indices of the
study, and then to compare area under the curve (AUC) of
these variables. For this purpose, the first measured profiles
before stenting were considered to be the values of patients with
significant aortic coarctation, while the next measured indices
after stenting were taken as the profiles of the individuals
without coarctation.
The cut-off points were then determined in each ROC
analysis. The best predictive cut-off value was the one that
gave the highest sensitivity and specificity simultaneously. The
diagnostic values of each cut-off point, including sensitivity
and specificity, were calculated and reported. All
p
-
values were
two-tailed and
p
<
0.05
was considered statistically significant.
Results
Twenty-three patients, including 16 (69.6%) males and seven
(30.4%)
females with a mean age of 26.14
±
10.17
years (range
14–56)
were enrolled in this study. The median time since
diagnosis of disease was 12.00 (IQR
=
31)
months and the
mean length of the stenosis was 20.44
±
10.47
mm. In addition,
the mean baseline ejection fraction was 54.55
±
5.10% (
range
35–60%)
and 16
±
69.6%
of patients were hypertensive. All
baseline and stenting characteristics of the patients are listed in
Table 1.
The patients underwent Doppler echocardiography at the time
of enrolment and after stenting. All Doppler echocardiographic
profiles of the abdominal and descending aorta (before and after
stenting) are given in Table 2. The differences between the two
measurements were calculated and mean percentages are listed
in Table 2.
TABLE 1. BASELINEAND STENTING
CHARACTERISTICS OF THE PATIENTS
Patients’ age (years)
26.14
±
10.17
Patients’ gender (%)
Male
16 (69.6)
Female
7 (30.4)
Blood pressure
Systolic blood pressure (mmHg)
158.18
±
24.18
Diastolic blood pressure (mmHg)
85.23
±
10.96
Time since diagnosis (months)
12.00 (
IQR
=
31)
Aortic valve (%)
BAV
13 (56.5)
TAV
10 (43.5)
Ejection fraction (%)
54.55
±
5.10
Length of the balloon (mm)
18.55
±
4.44
Width of the balloon (mm)
5.350
±
3.95
Length of the stent (mm)
37.16
±
3.67
Width of the stent (mm)
8.47
±
1.94
Peak before-stenting gradient of the catheter (mmHg)
57.05
±
12.69
Peak after-stenting gradient of the catheter (mm Hg)
2.38
±
5.39
Before-stenting gradient of the catheter (%)
85.00
±
7.69
After-stenting gradient of the catheter (%)
14.17
±
9.96
Length of the stenosis (mm)
20.44
±
10.47
All values for continuous variables are mean
±
SD except for time since
diagnosis, which is median (IQR).
