CARDIOVASCULAR JOURNAL OF AFRICA • Vol 24, No 5, June 2013
156
AFRICA
Statistical analysis
Data analysis was carried out using the statistical software
package (SPSS, Rel 13.0, Chicago: SPSS Inc.). Continuous
data were presented as mean
±
SD. Differences between
the NSTEMI and control groups were assessed by unpaired
Student’s
t-
test. Categorical parameters are presented as numbers
(%), and were analysed using chi-square tests or Fisher’s
exact tests, as appropriate. For assessment of intra- and inter-
observer variabilities, the Bland-Altman method was used.
11
The correlation between two variables was assessed using
Spearman’s rank correlation coefficient. A two-tailed
p
-value
<
0.05 was considered significant for statistical inference.
Results
The main clinical features and 2DDoppler echocardiography data
of the controls and NSTEMI patients are summarised in Tables 1
and 2, respectively. There were significant differences in clinical
features, such as hypertension, diabetes and hyperlipidaemia
between patients and healthy subjects. Patients with NSTEMI
had significantly increased LAV
max
(60.38
±
17.64 vs 45.33
±
14.50 ml,
p
=
0.001), LAV
min
(25.56
±
12.59 vs 16.18
±
8.93
ml,
p
=
0.001), and LAV
p
(43.80
±
16.59 vs 27.32
±
10.74 ml,
p
=
0.001), but significantly lower in LAPEF (28.96
±
11.62
vs 39.89
±
13.65%,
p
=
0.001), LA total EF (59.06
±
13.44 vs
65.53
±
10.20%,
p
=
0.013) and LVEF (58.08
±
10.01 vs 65.18
±
5.22%,
p
=
0.001).
The SR imaging of LA and LV was acceptable in all 40 healthy
subjects, whereas four had one inadequately traced segment. The
SR imaging of LA and LV was acceptable in 51 patients, whereas
five had one inadequately traced segment. Twenty healthy
subjects and 20 patients with NSTEMI were randomly selected
for the assessment of intra- and inter-observer variabilities in
the measurements of LA-GLSRs, LA-GLSRe, LA-GLSRa,
LV-GLSRs, LV-GLSRe and LV-GLSRa, respectively.
Bland-Altman analysis of these parameters showed no
evidence of any systematic difference regarding inter- and intra-
observer variabilities. Table 3, and Figs 3 and 4 show the mean
difference and confidence intervals of inter- and intra-observer
variabilities.
Table 4 lists the SR imaging echocardiographic variables of
the normal and NSTEMI groups. Compared with the controls,
patients with NSTEMI had significantly decreased LA-GLSRs
(
p
=
0.001), LA-GLSRe (
p
=
0.001), LV-GLSRs (
p
=
0.004), and
LV-GLSRe (
p
=
0.001).
Correlations of LA-GLSRs, LA-GLSRe, LA-GLSRa,
LV-GLSRs, LV-GLSRe and LV-GLSRa with parameters of LA
volume and function in NSTEMI patients were performed (Table
5). LA-GLSRs showed modest correlations with parameters of
LA volume and function, including LAV
max
(
r
=
–0.610,
p
<
0.01), LAV
min
(
r
=
–0.668,
p
<
0.01), LAV
p
(
r
=
–0.638,
p
<
0.01),
LAPEF (
r
=
0.376,
p
<
0.01), LAAEF (
r
=
–0.303,
p
<
0.05), LA
total EF (
r
=
–0.412,
p
<
0.05) and LVEF (
r
=
–0.334,
p
<
0.05).
TABLE 2. CONVENTIONAL 2D DOPPLER ECHOCARDIOGRAPHIC
PARAMETERS IN PATIENTSWITH NSTEMI AND THE CONTROLS
Controls
(
n
=
40)
NSTEMI
(
n
=
51)
p
-value
LAV
max
(ml)
45.33
±
14.50
60.38
±
17.64
0.001
LAV
min
(ml)
16.18
±
8.93
25.56
±
12.59
0.001
LAV
p
(ml)
27.32
±
10.74
43.80
±
16.59
0.001
LAPEF (%)
39.89
±
13.65
28.96
±
11.62
0.001
LAAEF (%)
42.74
±
11.25
43.89
±
11.67
0.637
LA total EF (%)
65.53
±
10.20
59.06
±
13.44
0.013
LVEF (%)
65.18
±
5.22
58.08
±
10.01
0.001
Date are expressed as mean ± SD.
TABLE 3. REPRODUCIBILITY OF LAAND LV GLOBAL STRAIN RATE
Controls
NSTEMI
Intra-observer Inter-observer Intra-observer Inter-observer
LA-GLSRs 0.94 (0.87–0.98) 0.95 (0.88–0.98) 0.95 (0.87–0.98) 0.98 (0.89–0.99)
LA-GLSRe 0.95 (0.88–0.98) 0.97 (0.91–0.99) 0.94 (0.87–0.98) 0.98 (0.90–0.99)
LA-GLSRa 0.94 (0.87–0.98) 0.96 (0.89–0.98) 0.94 (0.87–0.98) 0.93 (0.87–0.98)
LV-GLSRs 0.94 (0.87–0.98) 0.94 (0.85–0.97) 0.82 (0.76–0.96) 0.85 (0.67–0.94)
LV-GLSRe 0.95 (0.88–0.98) 0.94 (0.86–0.97) 0.93 (0.84–0.97) 0.92 (0.81–0.95)
LV-GLSRa 0.93 (0.84–0.97) 0.95 (0.88–0.97) 0.86 (0.80–0.98) 0.93 (0.85–0.97)
LA-GLSRs = LA global longitudinal peak positive strain rate during ventricular
systole, LA-GLSRe = LA global longitudinal peak negative strain rate during
early ventricular diastole, LA-GLSRa = LA global longitudinal and peak negative
strain rate during late ventricular diastole, LV-GLSRs =LV global longitudinal peak
systolic strain rate, LV-GLSRe = LV global longitudinal early diastolic strain rate,
LV-GLSRa = LV global longitudinal late diastolic strain rate. Date are expressed as
mean ± SD.
Fig. 3. Bland-Altman plots of inter-observer agreement
for LA-GLSRs in patients with NSTEMI.
2.00
1.00
0.00
–1.00
1.750
2.000 2.250 2.500 2.750 3.000
Mean inter-observer’s difference in LA-SRs
Mean LA-SRs (two observers)
Fig. 4. Bland-Altman plots of intra-observer agreement
for LA-GLSRs in patients with NSTEMI.
2.00
1.00
0.00
–1.00
–2.00
–3.00
–4.00
1.000
1.500 2.000 2.500 3.000 3.500
Mean intra-observer’s difference in LA-GLSRs
Mean LA-GLSRs (one observer)
