CARDIOVASCULAR JOURNAL OF AFRICA • Vol 21, No 3, May/June 2010
176
AFRICA
Aspirin in primary prevention: USPSTF recommendations
Recent clinical studies such as the Japanese
Primary Prevention trial (JPAD)
1
and the
Aspirin forAsymptomaticAtherosclerosis
study (AAA)
2
have resulted in considera-
ble debate on when and for whom aspirin
should be given as primary prevention for
vascular events.
The US Preventative Services Task
Force (USPSTF) has recently updated
its recommendations from new evidence
on the benefit and harm of aspirin for
the primary prevention of cardiovascular
disease, including myocardial infarction
and stroke.
3
All their recommendations
are allocated a graded level to indicate
the extent of data available to support the
advocated approach in both adult men
and women without a history of coronary
artery disease or stroke.
In men, the USPSTF recommends the
use of aspirin for men aged 45 to 79 years
when the potential benefit due to a reduc-
tion in myocardial infarctions outweighs
the potential harm due to an increase in
gastrointestinal bleeding. In younger men
(45–59 years), the benefits outweigh the
increased bleeding at a 10-year coronary
heart disease (CHD) risk of greater than
4%. In the older age group, under 80
years, the benefit–risk ratio is at 9 to
12% of the 10-year cardiovascular risk as
measured by a Framingham Heart study-
derived risk-assessment tool.
4
In women, the USPSTF recommends
the use of aspirin for women aged 55 to
79 years when the potential benefit of a
reduction in ischaemic strokes outweighs
the bleeding risk. In women aged 55 to
59 years, estimated harm is balanced by
benefit at a 2% 10-year stroke risk; which
rises to 11% in the age group 60 to 69
years and 17% in the under 80-year-old
group. Table 1 summarises these benefit–
risk balances.
A key issue for the practising clinician
is when to recommend against taking
aspirin. In an editorial in the
Annals of
Internal Medicine
,
5
Mehta pointed out
that the rule of benefit outweighing risk
assumes that patients place the same
value on avoiding a bleeding event as
they do on avoiding a stroke or myocar-
dial infarction. Depending on where the
bleeding occurs, some patients would
rather avoid a stroke than avoid a bleed-
ing event and would therefore prefer to
take aspirin. Discussing benefits and risks
with the individual patient is therefore
essential. Clearly also, patients at rela-
tively high risk for intracranial bleeding
should absolutely avoid aspirin.
Aspirin is still underused and these
USPSTF recommendations should assist
clinicians to extend the benefits of aspirin
to more patients.
J Aalbers, Special Assignments Editor
Ogawa H,
1.
et al
.
J Am Med Assoc
2008;
300
:
2134–2141.
ESC Congress 2009. Fowkes FGR. For the
2.
Aspirin for Asymptomatic Atherosclerosis
Trialists.
US Preventative Services Task Force.
3.
Ann
Intern Med
2009;
150
(6): 396–413.
Wilson PW, D’Agostino RB, Levy D,
4.
Belanger AM, Silbershatz H Kannel WB.
Circulation
1998;
97
: 1837–1847.
US Preventative Services Task Force.
5.
Ann
Intern Med
2009;
150
: 414–416.
TABLE 1. TEN-YEAR CHD RISK LEVELS
ATWHICHTHE NUMBER OF CVD
EVENTS PREVENTED IS CLOSELY
BALANCED TOTHE NUMBER OF
SERIOUS BLEEDING EVENTS
Men
Women
Age
(years)
10-year CHD
risk (%)
Age
(years)
10-year stroke
risk (%)
45–59
≥
4
55–59
≥
3
60–69
≥
9
60–69
≥
8
70–79
≥
12
70–79
≥
11
Adapted from
Ann Intern Med
2009;
150
(6): 396–404.
Tirofiban shows better platelet inhibition in diabetic patients
during PCI procedures
The extent of platelet aggregation and
levels of C-reactive protein (CRP)
released during actual percutaneous coro-
nary intervention (PCI) procedures have
not been well studied.
In this recently published randomised,
double-blind study of consecutively eligi-
ble patients, rapid-function platelet assays
were used to measure platelet aggrega-
tion, together with simultaneous measure-
ment of CRP, to compare the efficacy of
platelet inhibition of tirofiban and abcixi-
mab. Clinical endpoints of the study were
death, non-fatal MI, target vessel revas-
cularisation (TVR) with coronary artery
bypass grafting or PCI within 30 days of
the procedure.
1
Tirofiban showed greater platelet inhi-
bition in the diabetic patients at the first
time point within the PCI procedure.
Overall platelet inhibition was similar
with the two agents, but there was a trend
towards less effective platelet inhibition
with abciximab.
Interestingly, measurement of the
inflammatory marker, CRP, was similar
with both drugs, but these measurements
were characterised by a wide variability
during the procedure. However, hs-CRP
demonstrated an inverse relationship with
platelet inhibition over time. The clinical
outcomes in the two groups were similar
but the small numbers of patients limited
the definitive assessment of any differ-
ence in the clinical impact of these agents.
The study medications were admin-
istered as a bolus plus infusion for two
hours, together with heparin, to achieve a
target activated clotting time of 200–250
sec/i. Abciximab was dosed as 0.25
µ
g/
kg bolus given immediately before the
PCI, followed by 0.125
µ
g/kg/min (max
10 mg) for 12 hours. A 10-
µ
g/kg bolus of
tirofiban was given, followed by a 0.15-
µ
g/kg/min infusion for 12 hours.
This ‘real-world’ situation, although
without the recently recommended 25-
µ
g/
kg bolus dose of tirofiban, points to the
value of achieving steady state before
beginning PCI and maintaining this over
time. This study was the first to assess
CRP levels during a PCI procedure, and
an inverse relationship was seen with
levels of hs-CRP to platelet inhibition.
J Aalbers, Special Assignments Editor
Saltzman AJ,
1.
et al
. The relative effects of
abciximab and tirofiban on platelet inhibition
and C-reactive protein during coronary inter-
vention.
J Invas Cardiol
2010;
22
(1): 2–6.
