SA JOURNAL OF DIABETES & VASCULAR DISEASE
ACHIEVING BEST PRACTICE
VOLUME 7 NUMBER 2 • JUNE 2010
77
Abnormal resting ECG
An abnormal resting ECG is also a useful marker. Q waves and
deep T-wave inversion can signify previous myocardial infarction.
In addition, non-specific ST–T wave changes appear to be a strong
predictor of silent ischaemia. Rajapolan,
et al.
48
showed that 43% of
diabetic patients with Q waves, and 26% of those with ST–T wave
abnormalities had high-risk myocardial perfusion scans. Among the
high-risk single photon emission computed tomography scans the
majority had prognostically important CAD.
Peripheral vascular disease
Rajapolan,
et al.
48
identified PVD as an important marker: 28% of
patients with PVD had a high-risk perfusion scan. Nesto,
et al.
49
suggested that the prevalence of silent ischaemia in asymptomatic
diabetic patients with PVD was 47%. Thirty-seven per cent had
evidence of a previous silent MI. Previous studies
50,51
have found a
high prevalence of CAD in diabetic patients with PVD.
Cardiac autonomic neuropathy
The presence of a postural drop in blood pressure suggests an
underlying CAN in diabetic patients. Other features may include
unexplained tachycardia or reduced heart rate variability. CAN is
associatedwith a poor prognosis in type 2diabetes
52
and an increased
prevalence of silent myocardial ischaemia and infarction.
53,54
A study
by O’Sullivan,
et al.
53
showed that the prevalence of silent ischaemia
in diabetic men with demonstrable autonomic neuropathy was
64.7% versus 4.1% in those without.
Erectile dysfunction
Recent studies have suggested ED to be an important marker of CAD
in diabetes. Ma,
et al.
55
showed that type 2 diabetic men, without
documented CAD, but with ED, had double the incidence of future
coronary heart disease events than those without ED (19.7/1 000
patient-years versus 9.5/1 000 patient-years). Gazzaruso,
et al.
56
confirmed a strong independent association between ED and silent
Figure 2.
Proposed algorithm for the diagnosis and management of silent ischaemia in the diabetic population. Positive exercise tolerance test is defined as > 2
mm of flat or downsloping ST depression in two or more adjacent leads.
Key:
BP = blood pressure; CAD = coronary artery disease; CAN = cardiac autonomic neuropathy; ECG = electrocardiogram; ETT = exercise tolerance test
DECISION TO INVESTIGATE DIABETIC
PATIENTS FOR SILENT ISCHAEMIA
1) Erectile dysfunction
2) Peripheral vascular disease
3) Postural drop in BP as marker of CAN
4) Abnormal ECG
5) High clinical suspicion
EXERCISE TOLERANCE TEST
POSITIVE
TEST
NEGATIVE
TEST
INTERMEDIATE
TEST
Confirm with Stress
Echo or Myocardial
Perfusion Scanning
CORONARY
ANGIOGRAPHY
PROGNOSTICALLY
IMPORTANT CAD
1) Revascularisation
2) Risk factor modification
3) Beta blockers to reduce
ischaemic load
NON-PROGNOSTICALLY
IMPORTANT CAD
1) Risk factor modification
2) Beta blockers to reduce
ischaemic load
NO SIGNIFICANT CAD
1) Risk factor modification
