Cardiovascular Journal of Africa: Vol 23 No 2 (March 2012) - page 20

CARDIOVASCULAR JOURNAL OF AFRICA • Vol 23, No 2, March 2012 74 AFRICA
at the University of Kinshasa Hospital. Ethical approval was
obtained from the institutional ethics review board and informed
consent was obtained from the study participants. Exclusion
criteria included ischaemic heart disease (IHD), acute coronary
syndrome (ACS), congestive heart failure (CHF, NYHA class II
or greater), valvular heart disease, cerebral infarction or transient
ischaemic attack (TIA).
Self-reported physical activity, alcohol use and smoking
habits, known duration of diabetes mellitus, current treatments
and measures of adiposity [body mass index (BMI) and waist
circumference] were obtained in all patients. Overweight and
obesity were classified as BMI ≥ 25 kg/m2 and ≥ 30 kg/m2,
respectively. Central obesity was categorised as waist circumfer-
ence > 102 cm in men and > 88 cm in women.
Blood pressure (BP) was measured in the supine position
using a mercury sphygmomanometer with an appropriate cuff on
the left arm; the average of two readings was used for statistical
analysis. Pulse pressure (PP) calculated as systolic blood pres-
sure (SBP) minus diastolic blood pressure (DBP) was considered
increased when > 60 mmHg.8 Hypertension was defined as BP >
140/90 mmHg or currently on antihypertensive treatment. Heart
rate was counted over a full minute.
A 12-hour overnight fasting venous blood sample was
collected for measurement of total cholesterol and its sub-frac-
tions [low-density lipoprotein cholesterol (LDL-C) high-density
lipoprotein cholesterol (HDL-C)], triglycerides (TG), plasma
glucose, serum uric acid and creatinine levels. LDL-C was
calculated according to the Friedewald formula.9 Dyslipidaemia
was an LDL-C level ≥ 2.6 mmol/l or HDL-C < 1.03 mmol/l or
TG > 1.69 mmol/l.
According to the NCEP-ATP III guidelines,10 the metabolic
syndrome (MS) was, in addition to diabetes, the presence of two
of the followings risk factors: BP > 130/85 mmHg or current
antihypertensive treatment, central obesity as defined above,
HDL-C < 1.03 mmol/l and/or TG > 1.69 mmol/l.
We computed glomerular filtration rate [creatinine clearance
(CrCl)] using the MDRD equation.11 Chronic kidney disease
(CKD) was a CrCl rate < 60 ml/min per 1.73 m2; it was strati-
fied into mild (CrCl > 60 ml/min per 1.73 m2 ), moderate (CrCl:
30–60 ml/min per 1.73 m2 ) and severe (CrCl < 30 ml/min per
1.73 m2).12 A uric acid level > 416 µmol/l defined hyperuricae-
mia. Proteinuria was a 24-hour urine protein excretion rate >
0.3 g.
Echocardiographic examination was performed with the
patient in the partial left lateral decubitus position using
an Acuson 128XP/10˝ machine with a 3.5-MHz transducer.
Two-dimensional guided M-mode measurements were obtained
as recommended by the American Society of Echocardiography
(ASE).13
We used the Devereux modified cubed formula to calculate
left ventricular mass (LVM).14 To account for gender and body
size variations, LVM was indexed to height2.7, with a boundary of
51 g/m2.7 to define LVH in both genders.15 Relative wall thickness
(RWT) was calculated as 2 × PWTD (posterior wall thickness,
diastolic)/LVIDD (left ventricular internal diameter, diastolic). It
was considered increased when > 0.45.16 RWT and left ventricu-
lar mass index (LVMI) were used to characterise LV geometry
as normal (normal LVMI and normal RWT), concentric remodel-
ling (normal LVMI and increased RWT), concentric hypertrophy
(increased LVMI and increased RWT) and eccentric hypertrophy
(increased LVMI and normal RWT). LV ejection fraction (LVEF)
was calculated using Tiechloz’s formula.17
Statistical analysis
Data are expressed as mean ± standard deviation (SD) or relative
frequency in per cent. The distribution of duration of hyperten-
sion and triglyceride levels being positively skewed, the non-
parametric Mann-Whitney test was used for these variables.
Chi-square and Student t-tests were used for comparing categori-
cal and normally distributed continuous variables, respectively.
Multiple regression models and the likelihood ratio method
were performed with LVH as the dependent variable for the
assessment of the strength and independence of association with
risk factors. Adjusted odds ratio (aOR) were calculated for each
variable from a model which included all these variables; the
resulting aOR allowed the direct comparison of the independent
effects of these variables to decide which variable has the greater
effect on LVH. All statistical analyses were performed with SPSS
for Windows, version 18.0. A p-value ≤ 0.5 was considered
statistically significant.
Results
Tables 1 and 2 show clinical and biological characteristics of
patients according to renal function. Mean age and duration
of diabetes were 58 ± 8 and 11 ± 8 years, respectively for the
whole group. BMI, waist circumference, SBP and DBP, and
plasma glucose levels averaged 26 ± 5 kg/m2, 95 ± 12 cm, 148
± 26 mmHg, 84 ± 13 mmHg, and 8.10 ± 3.31 mmol/l, respec-
tively. Diabetes was frequently associated with other CV risk
factors, among which hypertension (80%) was the common-
est. Clustering of risk factors into the metabolic syndrome was
observed in 58% of patients.
Besides antidiabetic therapy, 97% of patients were receiving
BP-lowering drugs. CKD was observed in 32 patients (53%),
20 of whom (62%) had a CrCl rate of 30 ml/min per 1.73 m2 or
higher. Compared to those with normal renal function, the dura-
tion of diabetes was longer (13 ± 8 vs 8 ± 6 years; p ≤ 0.001), the
proportion of patients on current antihypertensive drugs greater
(42 vs 25%; p < 0.05) and the level of uric acid higher (450 ±
166 vs 306 ± 107 µmol/l; p ≤ 0.001) in CKD patients. The two
subgroups were similar for the other variables.
Table 3 summarises echocardiographic measurements by
renal function status and Table 4 by the severity of renal dysfunc-
tion. Patients with CKD had increased LVIDD (47.00 ± 6.00
vs 43.00 ± 7.00 mm; p ≤ 0.001), LVMI (47.00 ± 19 vs 36.00 ±
15.00 mm; p ≤ 0.05) and higher proportions of LVH (37 vs 14%;
p ≤ 0.05); they also showed higher proportions of concentric
(22 vs 11%; p ≤ 0.05) and eccentric (15 vs 3%; p ≤ 0.05) LVH.
Compared to patients with moderate CKD, those with severe
CKD had increased interventricular septum thickness, diastolic
(IVSD) (12.30 ± 3.08 vs 9.45 ± 1.94 mm; p ≤ 0.001), RWT (0.52
± 0.17 vs 0.40 ± 0.07 mm; p ≤ 0.01) and higher proportions of
LVH (50 vs 30%; p ≤ 0.05). Concentric remodelling (25 vs 15%;
p ≤ 0.05) and concentric hypertrophy (42 vs 10%; p ≤ 0.05) were
the geometric patterns most frequently encountered in patients
with severe CKD. Between groups, systolic function indices did
not differ.
In multivariable adjusted analysis, the probability of LVH