EDITORIAL
SA JOURNAL OF DIABETES & VASCULAR DISEASE
48
VOLUME 7 NUMBER 2 • JUNE 2010
The heart in diabetes
JA KER
D
iabetes mellitus is associated with a two- to four-fold
increased risk of coronary artery disease, and in diabetic
people, about two-thirds of deaths are cardiovascular
(ischaemic heart disease, congestive heart failure and stroke).
1
Some
have suggested diabetes mellitus to be a coronary heart disease risk
equivalent (having the same event rates as people without diabetes
but with prior cardiovascular disease).
2
However, this concept
remains controversial, especially in younger patients.
In the Interheart study, a standardised, case-control study in
52 countries of the risk factors for acute myocardial infarction,
diabetes had an odds ratio of 2.37 with a population-attributable
risk of 9.9%.
3
The Reach Registry, a prospective international
observational registry of 68 236 patients with three or more
cardiovascular risk factors or established atherothrombotic disease,
had 30 043 participants with diabetes.
4
The one-year cardiovascular
event rate was 40% higher in the diabetic patients than in the non-
diabetic patients.
The telomere length (on the far end of chromosomes) of
leucocytes are shortened in persons with type 2 diabetes mellitus
compared to healthy subjects, and even shorter in type 2 diabetes
mellitus patients with coronary heart disease.
5
Leucocyte telomere
length might be a useful marker of tissue ageing and progression
of both cardiovascular disease and diabetes.
Although chest pain (angina, acute coronary syndrome) is
considered to be a cardinal symptom of myocardial ischaemia, both
silent (asymptomatic) myocardial infarction and silent ischaemic
episodes (as seen on Holter testing) are more common in diabetic
patients, with a higher risk of cardiac events, including death. The
prevalence of silent ischaemia in non-diabetic patients may range
from 0.89 to 4% whereas in diabetic patients it is estimated to be
10 to 20%.
6
A meta-analysis of 12 studies demonstrated a consistent
association between cardiac autonomic neuropathy (CAN) and
painless (silent) myocardial ischaemia, with a pooled rate of
prevalence risk of 1.96 (95%CI: 1.53–2.51,
p
<
0.001) out of a total
of 1 468 patients.
7
Given the high prevalence of silent ischaemia
in diabetics, an attractive but controversial concept is that of
screening of asymptomatic diabetics. Some risk factors may assist
in the decision of who to screen: conventional cardiovascular risk
factors, breathlessness on exertion, abnormal resting ECG, presence
of peripheral vascular disease, cardiac autonomic neuropathy and
erectile dysfunction.
6
Diabetes is associated with cardiovascular risk factors
including hypertension, dyslipidaemia, hypercholesterolaemia and
abnormalities in fibrinolysis. In particular, hypertension is a major
co-morbid condition for diabetes and an important risk factor for
the development of cardiovascular and renal disease in diabetic
patients. The co-existence of hypertension and diabetes provides
an additive increase in the risk of vascular events: the concept of
‘terrible twins’. The Swedish Gotteborg study found that men over
25 years of age with both conditions had a 66% greater risk of
stroke or myocardial infarction compared to men with hypertension
alone.
8
Recent clinical trials with anti-hypertensive therapy stressed
the need to use drugs that did not increase the risk of developing
diabetes during treatment.
The Framingham Heart study showed heart failure to be twice
as prevalent in diabetic men and five times as common in diabetic
women aged 45 to 74 years than in age-matched control subjects.
9
The cardiotoxic triad: myocardial ischaemia, hypertension and
diabetic cardiac autonomic neuropathy, has led to the recognition
of a specific cardiomyopathy of diabetes.
10
Pathophysiological remodelling of the heart, ischaemia of the
ventricle, hypertensive heart disease, left ventricular hypertrophy,
diastolic dysfunction and diabetic cardiomyopathy alone or
collectively are responsible for the high risk of heart failure in diabetic
patients.
11
Recently, diastolic heart failure (i.e. heart failure with
normal ejection fraction) has been recognised as a major adverse
manifestation of hypertension and diabetes. However, convincing
therapeutic strategies other than strict risk factor control are still
lacking.
11
In conclusion, diabetes mellitus could be regarded also as a
cardiovascular condition.
References
Beckman JA, Creager MA, Libby P. Diabetes and atherosclerosis: epidemiology,
1.
pathophysiology and management.
J Am Med Assoc
2002;
287
: 2570–2581.
Haffner SM, Letito S, Rönnemaa T, Pyörölö K, Loakso M. Mortality from coronary
2.
heart disease in subjects with type 2 diabetes and in non-diabetic subject with
and without prior myocardial infarction.
N Engl J Med
1998;
339
: 229–234.
Yusuf S, Hawken S, Junpuu S, Dans T,
3.
et al
. Effect of potentially modifiable risk
factors associated with myocardial infarction in 52 countries (Interheart Study):
case-control study.
Lancet
2004;
364
: 937–952.
Krempf M, Parhofer KG, Steg G, Bhatt DL,
4.
et al
. Cardiovascular event rates in
Correspondence to: JA Ker
Department of Internal Medicine, University of Pretoria, Pretoria
Tel: 27 (0)12 354-1121
Fax: 27 (0)12 329-1351
e-mail:
S Afr J Diabetes Vasc Dis
2010;
7
: 48–49
Prof J Ker
