CARDIOVASCULAR JOURNAL OF AFRICA • Vol 23, No 8, September 2012
436
AFRICA
(
HbA
1
c
)
levels were measured on spot; blood glucose by a
HemoCue AB glucose analyser (Angelholm, Sweden) and
HbA
1
c
using a DCA 2000+ analyser (Bayer Inc., New York,
USA). Urinary albumin/creatinine ratio (UACR) was measured
in a spot morning urine sample using the same DCA 2000+
analyser, which measures urine albumin (in mg/l) and creatinine
(
in mg/dl) concentrations and calculates the urine albumin-
to-creatinine ratio (UACR). Microalbuminuria was defined as
UACR
>
30
mg/g and macroalbuminuria as UACR
>
300
mg/g.
13
Biochemical tests were performed with the use of a chemistry
analyser (Abbott Architect, Illinois, USA) at Muhimbili National
Hospital laboratory, which is the National reference laboratory.
All patients gave written informed consent. The study was
ethically approved by the Muhimbili University of Health and
Allied Sciences’ research and publication committee.
All echocardiograms were performed by the same licensed
cardiologist,whohadreceivedspecialtraininginechocardiography
(
PC), using a SONOS 7500 Phillips echocardiogram machine.
Patients were examined in the left lateral decubitus position
using a 3-MHz transducer. The echocardiographic protocol
included parasternal long- and short-axis views of the left
ventricle, left atrium and aorta, as well as two-, three- and
four-chamber images of the left ventricle and pulsed Doppler
recordings of LV filling. Spectral tissue Doppler was recorded
of mitral annular plane velocity in the apical four-chamber view.
All images were recorded digitally on Magnetic Optical
disks, and interpretation of all digital echocardiograms was done
at the Department of Heart Diseases, Haukeland University
Hospital using a Tomtec (TomTech Imaging Systems GmbH,
Unterschielssheim, Germany) work station for post-processing.
All studies were first read by the primary investigator and then
proof read by the senior investigator, a highly experienced reader
(
EG).
Quantitative echocardiography was performed following
the American Society of Echocardiography guidelines.
14
LV
hypertrophy was considered present when LV mass indexed for
height
2.7
exceeded 49.2 g/m
2.7
in men and 46.7 g/m
2.7
in women.
15
RWT was calculated as the ratio of end-diastolic posterior wall
thickness to end-diastolic LV internal radius and considered
increased if
≥
0.43.
Patients were categorised into four LV geometric patterns
based on LV mass/height
2.7
(
LVMI) and RWT measurements
in combination. Normal geometry was considered present if
LVMI and RWT were both normal, concentric remodelling was
the combination of normal LVMI and increased RWT, eccentric
hypertrophy was the combination of LV hypertrophy and
normal RWT, and concentric LV hypertrophy was present if LV
hypertrophy and increased RWT were both present.
14
LV circumferential end-systolic stress (CESS) was estimated
at the midwall using a cylindrical model.
16
Myocardial
contractility was assessed by midwall fractional shortening
(
MWS), calculated using a previously validated formula, taking
into consideration the epicardial migration of the midwall
during systole.
17
Stress-corrected fractional shortening (scFS)
and stress-corrected MWS (scMWS) were calculated as the ratio
between actual and predicted FS and MWS for actual CESS,
respectively, using previously published equations.
17
Transmitral flow was recorded with pulsed-wave Doppler
between the mitral cusp tips in the apical four-chamber view. The
early (E) and atrial (A) waves were traced for peak velocities and
used to calculate the E/A ratio. Isovolumic relaxation time was
measured from the leading edge of the aortic valve closure spike
to the leading edge of the mitral valve high-intensity echo in
five-chamber view. Early diastolic mitral annular plane velocity
(
E
′
)
was measured by spectral tissue Doppler in the apical four-
chamber view.
18
Statistical analysis
Data management and statistical analysis was performed using
SPSS for Windows version 18.0. Data are presented as mean ±
SD for continuous variables and as percentages for categorical
variables. Groups of patients were compared using the
χ
2
test
for categorical variables and unpaired Student’s
t
-
test, one way
ANOVA with Sheffe’s
post hoc
test or general linear model with
Sidak’s
post hoc
test for continuous variables, as appropriate.
Bivariate correlations were assessed by Pearson’s correlation
coefficients. Covariates of increased RWT were identified in the
total study population and in groups of type 1 and type 2 diabetes
patients by multiple linear regression analyses, run with an enter
procedure and co-linearity statistics. A two-tailed
p
-
value
≤
0.05
was considered statistically significant.
Results
The study population included 61 type 1 and 123 type 2 diabetes
patients. Compared to type 1 patients, type 2 patients were older,
had longer duration of diabetes and included more hypertensive
and obese patients (all
p
<
0.01) (
Table 1).
Compared to type 1 diabetes patients, type 2 patients had
larger LV dimensions and higher RWT and LVMI (Table 2).
LV systolic chamber function measured as stress-corrected
fractional shortening and ejection fraction did not differ between
the two groups, while myocardial contractility assessed by stress-
corrected midwall shortening was significantly lower among
type 2 diabetes patients (Table 2). Measures of diastolic function
were also significantly unfavourable in the type 2 diabetes
patients (Table 2). However, LV dimension and function did not
differ between the two types of diabetes when adjustment for age
and systolic blood pressure was done (Table 2).
In the total population, the prevalence of concentric
remodelling, eccentric hypertrophy and concentric hypertrophy
was 32, 8.3 and 23.7%, respectively. LV geometry differed
significantly between type 1 and type 2 diabetes patients as a
consequence of more type 2 diabetes patients having concentric
LV hypertrophy (Fig. 1). Systolic blood pressure and body mass
index were among the most important covariates of LV geometry
in the total study population (Figs 2, 3).
In logistic regression analysis involving the total study
population, LV hypertrophy (combined eccentric and concentric
LV hypertrophy) was associated with obesity, (OR 3.97, 95%
CI: 1.65–9.54,
p
=
0.002),
hypertension (OR 4.58, 95% CI:
1.32–15.85,
p
=
0.016)
and albuminuria (OR 2.31, 95% CI:
1.01–5.27,
p
=
0.047).
This was independent of age, gender, type
or duration of diabetes (Table 3).
The most prevalent types of abnormal LV geometry were
concentric remodelling in type 1 diabetes patients and concentric
LV hypertrophy in type 2 diabetes patients (Fig. 1). Overall, 58%
of the total population had increased RWT. In univariate linear
regression analysis, the most important correlates of higher
RWT were older age, higher blood pressure and higher log
