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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 29, No 5, September/October 2018
284
AFRICA
Exclusion criteria were hypertension (blood pressure
≥
140/90 mmHg or use of antihypertensive drugs), age above
65 years, macroalbuminuria, serum creatinine of
≥
1.5 mg/
dl, chest deformity or long-standing chest disease evidenced
on chest X-ray, sickle cell disease, urinary tract infection,
pregnancy, cardiac conditions such as arrhythmia, heart failure,
valvular heart disease, pericardial disease, congenital heart
disease, and ischaemic heart disease as evidenced by clinical,
electrocardiographic and echocardiographic features.
Age, gender and duration of diabetes were recorded for
each subject. Weight was determined in kilograms (kg) using
a weighing scale, height using a stadiometer, and waist and hip
circumferences (WC and HC) were measured in centimetres (cm)
using a tape measure. Body mass index (BMI), body surface area
(BSA) and waist:hip ratio (WHR) were calculated.
Blood pressure was measured using an Accosson mercury
sphygmomanometer with appropriate sized cuff at the brachial
artery, Korotkoff phase 1 was used for systolic (SBP) and phase
5 for diastolic blood pressure (DBP) after at least 15 minutes
of rest in a sitting position. Pulse rate (PR) was measured at
the radial artery. The mean of three consecutive measurements,
taken at five-minute intervals, was recorded. An overnight
fasting venous blood sample was collected for measurement of
levels of plasma glucose, creatinine and urea, and lipid profile
using standard protocols.
A two-step microalbuminuria screening process was
conducted. Combur 10 test strip (Roche Diagnostics, Mannheim,
Germany), a visual colorimetric semi-quantitative urine test
strip, was used to test for protein, blood, nitrite and leucocyte
levels. If all were absent then detection of microalbuminuria was
performed on the same urine sample.
Microalbuminuria was determined using Micral test strips, an
optically read semi-quantitative immunoassay method (Roche
Diagnostics, Australia) with a sensitivity and specificity of 80
and 88%, respectively.
11
There are four colour blocks on the
test strip corresponding to negative (or 0), 20, 50 and 100 mg/l
of albumin. The test was done on two occasions; the first was
random urine samples (RUS) and the second was first morning
void (FMV) urine samples of the subjects.
Microalbuminuria was considered to be present when the
two urine samples produced a reaction colour corresponding
to 20 mg/l or more. The result from the FMV urine sample was
recorded as the MCA status of the subject. It has been suggested
that MCA detected in the FMV urine sample corresponds
better with 24-hour urinary albumin excretion (UAE) than
microalbuminuriameasured in a RUS, because it is less influenced
by physical exercise and diet.
12
Echocardiographic examination was performed with the
patient in the left lateral decubitus position using a Hewlett-
Packard Sonos 4500 echocardiography machine with a 3.5-MHz
transducer. Measurements were taken under two-dimensional
guided M-mode, as recommended by the American Society of
Echocardiography (ASE).
13
Endocardial fractional shortening (FS) was calculated
automatically by the echocardiography machine using the
formula:
14
FS
=
LVIDd – LVIDs
_____________
LVIDd
×
100
where LVIDd is left ventricular internal dimension in diastole
and and LVIDs is left ventricular internal dimension in systole.
Left ventricular end-diastolic and end-systolic volumes
(LVEDV and LVESV) were calculated automatically by
the echocardiography machine from M-mode-derived LV
dimensions, using Teicholz’s formula:
LVEDV or LVESV
=
7.0
×
LVID
3
__________
2.4
+
LVID
Ejection fraction (EF) was calculated using the formula:
EF
=
EDV – ESV
__________
EDV
×
100
The LV systolic function was considered normal if the EF
was greater than 50% and/or FS was greater than 25%.
14
The LV
diastolic function was assessed using Doppler modalities. Early
(E) and atrial (A) velocities as well as deceleration time (DT)
were measured using pulsed-wave Doppler by placing the sample
volume at the tips of the mitral leaflets in apical four-chamber
view. Isovolumic relaxation time (IVRT) was measured as the
time interval from the end of LV outflow and start of LV inflow,
as indicated by simultaneous registration of outflow and inflow
signals by high-frequency pulsed-wave Doppler.
Pulmonary venous flow (PVF), systolic (S), diastolic (D) and
atrial reversal (Ar) velocities were obtained by placing a pulsed-
wave Doppler sample volume 1–2 cm into the pulmonary vein,
proximal to its insertion into the left atrium. E/A and S/D were
calculated.
Diastolic function (DF) was categorised into grades according
to its progression to diastolic dysfunction (DD):
•
normal DF: E/A between 1 and 2, IVRT 60–100 ms and DT
160–240 ms
•
grade 1 DD: E/A
<
1, IVRT
>
100 ms, DT
>
240 ms
•
grade 2 DD: E/A 1– 2, IVRT 60–100 ms, DT 150–220 ms,
PVFS/D
<
1
•
grade 3 DD: E/A
>
2, IVRT
<
60 ms, DT
<
160 ms.
15
where DT is deceleration time and PVFS is pulmonary venous
flow S velocity.
Pulmonary artery systolic pressure (PASP) was estimated from
peak tricuspid regurgitant flow using continuous-wave Doppler.
Tissue Doppler echocardiography was not used because, at the
time the study was conducted, the echo machine used did not
have the facility.
Statistical analysis
Data obtained were analysed using STATA 10. Continous
variables are expressed as mean (
±
standard deviation) and
categorical variables as percentages. Categorical variables were
analysed using the chi-squared test. Student’s
t
-test and analysis
of variance (ANOVA) were used to analyse continuous variables.
Correlates of LV function were determined using Pearson’s rank
correlation and predictors were assessed using logistic regressions.
A
p
-value
≤
0.05 was considered statistically significant.
Results
One hundred and ninety-three participants comprising 63
T2DM patients with normoalbuminuria, 71 T2DM with
microalbuminuria and 59 controls were studied. The mean age
for all participants was 50 years and the three groups were age
and gender matched. Table 1 shows the clinical characteristics
of the three study groups. The duration since diagnosis of DM
was significantly longer in the microalbuminuric than in the