26 / 44
RESEARCH ARTICLE
SA JOURNAL OF DIABETES & VASCULAR DISEASE
24
VOLUME 15 NUMBER 1 • JULY 2018
Transthoracic echocardiographic examinations were performed
using a commercially available cardiac ultrasound scanner (Acuson
Sequoia 512 system with 2.5–4.0 MHz transducer, Siemens
Mountain View, California, USA) in the left lateral position, according
to the criteria of the American Society of Echocardiography.
16
During
echocardiography a continuous one-lead ECG recording was done.
Left ventricular end-diastolic and end-systolic volumes were
determined in the apical view, and stroke volume and EF were
measured using the modified Simpson’s equation.
16
LV mass (LVM)
was calculated with the Devereux formula as:
LVM (g) = 1.04 [(LVID + PWT + IVST)³ – LVID³] – 14
Where LVID = LV internal dimension; PWT = posterior wall
thickness; IVST = interventricular septum thickness. LVM was
indexed to body surface area (BSA) by dividing LVM by BSA.
Peak early diastolic (E) velocity, atrial contraction (A) velocity
and E-wave deceleration time (DT) were measured from the
transmitral pulsed-wave Doppler spectra, and the E/A ratio
was calculated. Pulsed-wave tissue Doppler imaging (TDI) was
performed in an apical four-chamber window with a sample
volume of 5 mm and the monitor sweep speed was set at
100 mm/s to optimise the spectral display of myocardial velocities.
All Doppler spectral velocities were averaged over three consecutive
beats. The average pulsed-wave TDI-derived early (E’) diastolic
myocardial velocity was obtained from the lateral and septal sides
of the mitral annulus. Then the E/E’ ratio was calculated to provide
an estimation of LV filling pressures.
17
The TDI-derived late-diastolic wave (A’) was obtained from the
mitral lateral annulus.
LA diameter was measured from the parasternal long axis
with M-mode echocardiography. LA volumes were traced and
calculated by means of the modified Simpson’s method from
apical four- and two-chamber views, according to the guidelines
of the American Society of Echocardiography and European
Association of Cardiovascular Imaging.
16
LA volumes were
measured as: (1) just before the mitral valve opening, at
end-systole (maximal LA volume or V
max
); (2) at the onset of the
P wave on electrocardiography (pre-atrial contraction volume or
Volp); and (3) at mitral valve closure, at end-diastole (minimal LA
volume or Vmin). From these, the following measurements were
calculated:
• LA passive emptying volume (PEV) = V
max
– V
olp
• LA passive emptying fraction (PEF) = PEV/V
max
x
100
• LA active emptying volume (AEV) = V
olp
– V
min
• LA active emptying fraction (AEF) = AEV/V
olp
x
100
• LA total emptying volume (TEV) = V
max
– V
min
• LA total emptying fraction (TEF) = TEV/V
max
x
100
Left atrial volumes were indexed to BSA in all patients.
18
Statistical analysis
Statistical analyses were performed with the MedCalc Statistical
Software version 12.7.7 (MedCal Software bvbv, Ostend, Belgium;
2013). All continuous variables are expressed as mean ± standard
deviation and median (minimum–maximum). All categorical
variables are defined as frequency and percentage. All continuous
variables were checked with the Kolmogorov– Smirnov normality
test to show their distributions. Continuous variables with normal
distributions were compared using the unpaired Student’s
t
-test,
while continuous variables with abnormal distributions were
compared using the Mann–Whitney
U
-test. For categorical
variables, the chi-squared test was used.
Pearson or Spearman’s correlation analyses were used to
determine the associations between LA volume and function, and
various laboratory parameters and 2D echocardiographic diastolic
parameters. Multivariate evaluations were performed using linear
regression analysis. The confounders that were found to have
a statistically significant impact on the dependent variable on
univariate analysis were described as the independent variables in
a multivariate linear regression analysis model. The p-values less
than 0.05 were considered significant.
Sample size justification: according to the article ‘Effects
of diabetes mellitus on left atrial volume and functions in
normotensive patients without symptomatic cardiovascular
disease’,8 the V value for DM2 patients was 40.9 ± 11.9 ml, and
for the control group, 34.6 ± 9.3 ml. The mean difference was
assumed as 6.3 ml; the standard deviation of the DM2 group was
11.9 ml and of the control group, 9.3 ml. With the assumption of
5% of type 1 error (a) and 80% power (1b), the sample size was
calculated at 46 patients for each group. With a 20% drop-out
rate, a minimum of 56 patients (112 in total) would have to be
enrolled in the study.
Results
The study population consisted of 112 subjects (52 male, mean
age 51.7 ± 7.0 years). Patient characteristics, analysed according
to the two groups, are shown in Table 1. The groups were similar
regarding age and gender. In the DM2 group, 44 (78.6%) patients
were hypertensive and 33 (58.9%) were receiving insulin and
oral antidiabetic agents. Patients in the DM2 group were also
taking more medications, such as acetylsalicylic acid, angiotensin
converting enzyme inhibitors, beta-blockers and statins than the
control group.
Body mass index (BMI) and levels of triglycerides (TG), high-
sensitivity C-reactive protein (hsCRP), uric acid, fasting glucose and
HbA
1c
were significantly higher in the DM2 group compared with
the control group (
p
< 0.05). There were no significant differences
regarding total cholesterol and low- (LDL) and high-density
lipoprotein (HDL) cholesterol levels between the groups (
p
> 0.05)
(Table 1).
Table 2 reports the results of 2D echocardiographic parameters
reflecting diastolic function with preserved systolic function. Twelve
(21.4%) subjects in the control group and 29 (51.8%) patients in
the DM2 group had some degree of diastolic dysfunction. Mitral A
wave, E/E’ ratio and mitral A’ wave were significantly higher, and
mitral E’ wave was significantly lower in the DM2 group compared
with the controls (
p
< 0.05).
There were no significant differences between the groups
regarding EF, mitral E wave and E/A ratio (
p
> 0.05). LA diameter,
and indexed Vmax, Volp, Vmin, AEV and TEV were found to be
significantly higher in the DM2 group compared with the controls
(
p
< 0.05). PEF was significantly lower in the DM2 group compared
with the controls (
p
< 0.05). Between the two groups, there were
no significant differences in indexed PEV, AEF and TEF (
p
> 0.05)
(Table 3).
Patients in the DM2 group were divided according to presence
of diastolic dysfunction. There were no significant differences
within the DM2 group regarding LA volume and function (
p
> 0.05)
(Table 4).