This paper addresses primary care physicians, cardiologists,
internists, angiologists and doctors desirous of
improving vascular risk prediction in primary care.
Many cardiovascular risk factors act aggressively
on the arterial wall and result in atherosclerosis and
atherothrombosis. Cardiovascular prognosis derived
from ultrasound imaging is, however, excellent in subjects
without formation of intimal thickening or atheromas.
Since ultrasound visualises the arterial wall directly,
the information derived from the arterial wall
may add independent incremental information to the
knowledge of risk derived from global risk assessment.
This paper provides an overview on plaque imaging for
vascular risk prediction in two parts:
Part 1: Carotid IMT is frequently used as a surrogate
marker for outcome in intervention studies addressing
rather large cohorts of subjects. Carotid IMT
as a risk prediction tool for the prevention of acute myocardial
infarction and stroke has been extensively
studied in many patients since 1987, and has yielded
incremental hazard ratios for these cardiovascular
events independently of established cardiovascular risk
factors. However, carotid IMT measurements are not
used uniformly and therefore still lack widely accepted
standardisation. Hence, at an individual, practicebased
level, carotid IMT is not recommended as a risk
assessment tool.
The total plaque area of the carotid arteries (TPA)
is a measure of the global plaque burden within both
carotid arteries. It was recently shown in a large Norwegian
cohort involving over 6000 subjects that TPA is
a very good predictor for future myocardial infarction
in women with an area under the curve (AUC) using a
receiver operating curves (ROC) value of 0.73 (in men:
0.63). Further, the AUC for risk prediction is high both
for vascular death in a vascular prevention clinic group
(AUC 0.77) and fatal or nonfatal myocardial infarction
in a true primary care group (AUC 0.79). Since TPA has
acceptable reproducibility, allows calculation of posttest
risk and is easily obtained at low cost, this risk assessment
tool may come in for more widespread use in
the future and also serve as a tool for atherosclerosis
tracking and guidance for intensity of preventive therapy.
However, more studies with TPA are needed.
Part 2: Carotid and femoral plaque formation as
detected by ultrasound offers a global view of the extent
of atherosclerosis. Several prospective cohort studies
have shown that cardiovascular risk prediction is
greater for plaques than for carotid IMT. The number
of arterial beds affected by significant atheromas may
simply be added numerically to derive additional information
on the risk of vascular events.
A new atherosclerosis burden score (ABS) simply
calculates the sum of carotid and femoral plaques encountered
during ultrasound scanning. ABS correlates
well and independently with the presence of coronary
atherosclerosis and stenosis as measured by invasive
coronary angiogram. However, the prognostic power of
ABS as an independent marker of risk still needs to be
elucidated in prospective studies.
In summary, the large number of ways to measure
atherosclerosis and related changes in human arteries
by ultrasound indicates that this technology is not yet
sufficiently perfected and needs more standardisation
and workup on clearly defined outcome studies before
it can be recommended as a practice-based additional
risk modifier.