CARDIOVASCULAR JOURNAL OF AFRICA • Volume 25, No 1, January/February 2014
AFRICA
17
The beginning of the P wave was defined as the point where
the initial deflection of the P wave crossed the isoelectric line,
and the end of the P wave was defined as the point where the
final deflection of the P wave crossed the isoelectric line. ECGs
with measurable P waves in less than 10 leads were also excluded
from the analysis. In all patients, derivations were excluded if the
beginning or ending of the P wave could not be clearly identified.
PD was calculated by subtracting the minimum P-wave duration
(P
min
) from the P
max
.
Statistical analysis
Statistical analyses were performed using SPPS software
(version 15.0, SPSS, Chicago, Illinois, USA). An assessment
of the normality was done initially with Kolmogorov–Smirnov.
All numerical data were expressed as mean
±
standard deviation
or median (interquartile range). Groups were compared by
Mann–Whitney
U
- or student
t
-tests. The relationship
between parameters was calculated using Pearson correlation
analysis. The intra-observer variability for the detection of
atrial electromechanical coupling was evaluated by Spearman’s
correlation;
p
-values
<
0.05 were considered significant.
Results
The laboratory and clinical characteristics of the subjects are
presented in Table 1. Mean age, heart rate, systolic and diastolic
BP, and glucose levels were similar in both groups. However,
haemoglobin levels were significantly lower in the pregnant
subjects (12.6
±
1.3 vs 13.3
±
1.1 mg/dl,
p
=
0.046) and body
mass index was higher in the pregnant subjects (26.8
±
2.4 vs
24.4
±
3.8 kg/m
2
,
p
=
0.006)
Echocardiographic results are listed in Table 2. The LV
end-diastolic and end-systolic dimensions, inter-ventricular
septum thickness, LV posterior wall thickness, LV ejection
fraction, LA diameter, and E velocity were similar in both
groups. However, the A velocity and DT were significantly
higher (81.3
±
17.5 vs 65.0
±
12.5 ms,
p
<
0.0001; 204.8
±
20.8
vs 193.5
±
15.9 ms,
p
=
0.007, respectively) in the pregnant
subjects than the controls. There were no significant differences
between the two groups with regard to Sm, Em, Am, IRT, ICT,
ET and MPI values (Table 2).
Intra-observer variability was assessed in 20 selected subjects
at random from the patient study group by repeating the
measurements under the same baseline conditions. Intra-observer
coefficients of variation for echocardiographic measurements
were found to be
<
5% and non-significant.
The atrial electromechanical coupling parameters of different
sites measured by TDI and P-wave measurements are shown in
Table 3. The PA lateral and PA septum were significantly higher
in the pregnant subjects compared with the controls (62.1
±
2.7
vs 55.3
±
3.2 ms, 45.7
±
2.5 vs 43.1
±
2.7 ms,
p
<
0.001). The
PA tricuspid did not differ significantly between the groups (
p
>
0.05). Furthermore, inter-atrial, intra-atrial and intra-left atrial
electromechanical coupling intervals were also prolonged in the
pregnant subjects compared the controls (26.4
±
4.0 vs
20.2
±
3.6 ms,
p
<
0.001; 10.0
±
2.0 vs
8.0
±
2.6 ms,
p
=
0.002; 16.4
±
3.3 vs 12.2
±
3.0 ms,
p
<
0.001, respectively).
P-wave measurements are given in Table 3. Both the P
max
and the PD were significantly longer in the pregnant subjects
(103.1
±
5.4 vs 96.8
±
7.4 ms,
p
<
0.001; 50.7
±
6.8 vs 41.6
±
5.5 ms,
p
<
0.001, respectively). In addition, a significant
positive correlation was found between inter-atrial and intra-left
atrial electromechanical coupling interval and P
max
(
r
=
0.282,
p
=
0.029,
r
=
0.378,
p
=
0.003, respectively).
In correlation analysis, no relationship was detected between
the atrial electromechanical coupling parameters and clinical
data such as age, heart rate, systolic and diastolic BP. However,
there were significant correlations between the inter-atrial and
intra-left atrial electromechanical coupling interval and the A
velocity (
r
=
0.459,
p
<
0.001,
r
=
0.448,
p
<
0.001, respectively)
(Fig. 2).
Table 1. Clinical and laboratory characteristics of the subjects
Pregnant subjects
Controls
p
-value
Age (years)
28
±
4
28
±
3
0.817
Heart rate (bpm)
83.0
±
10.8
80.2
±
9.5
0.293
BMI (kg/m
2
)
26.8
±
2.4
24.4
±
3.8
0.006
Glucose (mg/dl)
89.9
±
10.0
90.9
±
10.9
0.706
Hgb (mg/dl)
12.6
±
1.3
13.3
±
1.1
0.046
SBP (mmHg)
116.5
±
12.3
116.5
±
10.5
0.991
DBP (mmHg)
74.6
±
7.1
74.2
±
7.0
0.828
BMI: body mass index, Hgb: haemoglobin, SBP: systolic blood pressure,
DBP: diastolic blood pressure.
Table 2. Echocardiographic and tissue Doppler
echocardiographic parameters
Parameters
Pregnant
subjects
Controls
p
-value
Echocardiographic parameters
LVEDD (mm)
45.4
±
3.2 45.9
±
4.0 0.579
LVESD (mm)
27.7
±
3.1 28.9
±
3.2 0.170
IVS thickness (mm)
9.8
±
0.6
9.6
±
1.1 0.427
PW thickness (mm)
8.6
±
0.6
8.6
±
1.2 0.900
LV mass
181.8
±
43.8 160.5
±
36.9 0.047
LV EF (%)
68.8
±
6.4 66.7
±
6.3 0.208
Left atrium dimension (mm)
33.0
±
4.0 32.6
±
4.9 0.753
Mitral E velocity (cm/s)
83.4
±
18.3 79.9
±
14.8 0.416
Mitral A velocity (cm/s)
81.3
±
17.5 65.0
±
12.5
<
0.001
DT (ms)
204.8
±
20.8 193.5
±
15.9 0.007
IVRT (ms)
90.1
±
12.3 86.2
±
5.4 0.223
Tissue Doppler parameters
Sm (cm/s)
11.1
±
2.4 10.6
±
1.7
0.395
Em (cm/s)
12.8
±
4.0 13.6
±
3.3 0.371
Am (cm/s)
12.1
±
2.4 10.8
±
2.7 0.070
E/Em
6.9
±
1.9
6.0
±
1.3 0.046
ICT (ms)
69.8
±
19.2 72.5
±
14.7 0.545
IRT (ms)
64.1
±
10.2 67.0
±
11.6 0.321
ET (ms)
267.1
±
31.2 281.8
±
29.2 0.065
MPI
50.4
±
9.2 49.8
±
7.8 0.785
LV: left ventricular; LVEDD: LV end-diastolic dimension; LVESD: LV
end-systolic dimension; IVS: interventricular septum; PW: posterior
wall; EF: ejection fraction; DT: mitral E-wave deceleration time; IRT:
isovolumetric relaxation time; Sm: mean LV systolic myocardial veloc-
ity; Em: mean LV myocardial early diastolic velocity; Am: mean LV
myocardial late diastolic velocity; ICT: mean LV isovolumetric contrac-
tion time; IRT: mean LV isovolumetric relaxation time; ET: mean LV
ejection time; MPI: myocardial performance index.
