VOLUME 9 NUMBER 3 • SEPTEMBER 2012
125
SA JOURNAL OF DIABETES & VASCULAR DISEASE
EVIDENCE IN PRACTICE
I
t is well known that diabetes is associated with concentric left
ventricular (LV) remodelling, and that LV hypertrophy is particularly
common in patients afflicted with both type 2 diabetes and
hypertension. The co-existence of diabetes and other cardiovascular
risk factors such as hypertension and obesity may contribute to
the association of diabetes with subclinical cardiac target-organ
damage. In the LIFE study, concentric LV remodelling was associated
with three and eight times increased risk, respectively, of stroke and
cardiovascular death after 4.8 years of follow up.
An increased prevalence of congestive heart failure and stroke
has been noted among black diabetic patients. Recent publications
arising out of sub-Saharan Africa report an increase in the prevalence
of diabetes, hypertension and other cardiovascular risk factors,
as well as a high prevalence of LV hypertrophy. The Strong Heart
study indicates that increased relative wall thickness (RWT) and LV
hypertrophy are more prevalent in diabetic African-Americans than
in diabetic Caucasians, with earlier development of cardiac end-
organ damage. However, there is a dearth of data on LV geometry
in diabetic populations from sub-Saharan Africa.
A study by Chillo and colleagues attempted to determine
the prevalence and covariates of abnormal LV geometry among
type 1 and 2 diabetic out-patients of African origin and made a
welcome contribution to current knowledge on diabetic heart
disease in this population.
1
Of particular importance to resource-
limited settings where echocardiography is not freely available, this
study indicates that a simple algorithm using routine clinical and
laboratory tests (type of diabetes, presence of hypertension, obesity
and albuminuria) may be used to identify 75% of high-risk diabetic
patients with increased RWT.
Results indicate that abnormal LV geometry is common in
diabetic sub-Saharan African patients; the most prevalent form
of which is concentric remodelling, associated with reduced LV
myocardial contractility and delayed diastolic relaxation. In the
total study population, the prevalence of concentric remodelling,
eccentric hypertrophy and concentric hypertrophy was 32, 8.3 and
23.7%,
respectively.
Abnormal LV geometry was found in 40% of type 1 diabetes
patients, most commonly concentric remodelling (30%). Chillo
et
al
.
1
explain the interesting finding of concentric LV hypertrophy
being most common in patients with type 2 diabetes (36.7%),
but entirely absent in type 1 diabetes study patients, by drawing
attention to the low prevalence of hypertension among the group
with type 1 diabetes.
Hypertension is a strong covariate of having both LV hypertrophy
and increased RWT. In the study, all type 1 diabetes patients with
LV hypertrophy (10%) displayed eccentric LV hypertrophy and also
had albuminuria, identifying albuminuria as a main covariate of LV
hypertrophy. From this, Chillo
et al
.
raise the question whether drugs
that inhibit the renin–angiotensin system will prevent progression
to LV hypertrophy among type 1 diabetes patients.
Age and systolic blood pressure were the primary confounders
of difference in LV structure between type 1 and 2 diabetes
patients. Hypertension, in particular isolated systolic hypertension,
increased in prevalence with aging, mainly as a consequence of
Early cardiac risk markers in diabetic African patients
Definitions
Hypertension was defined as blood pressure ≥ 140/90 mmHg
•
or use of antihypertensive medications.
Microalbuminuria was defined as a urinary albumin:creatinine
•
ratio (UACR) > 30 mg/g and macroalbuminaria as UACR >
300
mg/g.
LV hypertrophy was considered present when LV mass
•
indexed for height (LVMI) exceeded 49.2 g/m
2.7
in men and
46.7
g/m
2.7
in women.
RWT was calculated as end-diastolic posterior wall
•
thickness:end-diastolic LV internal radius ratio. RWT was
considered increased if ≥ 0.43.
LV geometric patterns were considered normal if LVMI and
•
RWT were both normal. Concentric remodelling was defined
as the combination of normal LVMI and increased RWT,
whereas the combination of LV hypertrophy and normal RWT
defined eccentric hypertrophy. Concentric LV hypertrophy
was indicated in the presence of both LV hypertrophy and
increased RWT.
arterial stiffening imposing increased load on the left ventricle.
Older age was particularly associated with increased RWT, and with
LV hypertrophy when hypertension co-existed.
Overall, increased RWT was present in 58% of the study patients.
Although higher RWT was significantly associated with older age
and higher blood pressure in this study, independent associations
between increased RWT and measures of systolic and diastolic
LV function were found irrespective of presence or absence of LV
hypertrophy or hypertension. This emphasises the need to further
stratify patients according to the different LV geometric patterns,
rather than by presence or absence of LV hypertrophy alone.
This is particularly important in the context of African diabetes,
as concentric remodelling was found to be the most common
abnormal LV geometric pattern.
Other significant findings of this study also associated higher
RWT in type 2 diabetes patients with lower serum high-density
lipoprotein (HDL) cholesterol, but not with triglyceride-to-HDL
cholesterol ratio. No independent association between gender and
measures of LV geometry was indicated, contrasting with findings
of the ARIC (Atherosclerosis Risk in Community) study conducted
in an African-American population.
In conclusion, Chillo
et al
.
1
found that a 76% chance of having
cardiac target-organ damage existed in the type 2 diabetes patients
with any of the risk factors of obesity, hypertension or albuminuria,
as well as in the type 1 diabetes patients having any two of these
three risk factors.
Reference
Chillo P, Lwakatare J, Lutale J, Gerdts E. Increased relative wall thickness is a
1.
marker of subclinical cardiac target-organ damage in African diabetic patients.
Cardiovasc J Afr
,
published online 20/3/12.
