CARDIOVASCULAR JOURNAL OF AFRICA • Vol 23, No 2, March 2012
116
AFRICA
elderly show that benefits are derived
early (within one year) and sustained
on treatment for a further year. People
over 80 years should have their blood
pressure checked regularly, and if they
have sustained levels over 160 mmHg
these should be treated to a target of
150 mmHg.
5
Reasonable targets for the frail older
patient are fasting plasma glucose
values of 7.0–8.9 mmol/l, HbA
1c
levels of
7.5–8.5% and blood pressure of < 150/
< 90 mmHg – Dr Sophia Rauff
Contrast nephropathy
Dr Graham Cassel
There is an increase in demand for radi-
ological tests such as CT scans with
contrast, due to an increase in the size of
the ageing population and an increase in
incidence of cardiovascular disease. There
is also an increase in the complexity of
procedures and patients (more co-morbid-
ities).
Contrast-induced acute kidney injury
is defined as an impairment of renal
function (or increase in serum creati-
nine levels
>
25%) within three days of
contrast administration, with no other
discernible cause. A risk score can iden-
tify high-risk patients prior to the proce-
dure. This includes elements such as
diabetes, contrast volume, serum creati-
nine level above 132 mmol/l, anaemia
and hypotension. Also important are age,
dehydration, and the use of high osmolar
contrast media. Consequences include
renal impairment that peaks four to five
days after contrast administration, longer
hospital stay, increased cardiac morbidity,
increased risk of death and greater risk of
longer-term mortality.
Estimated or measured glomeru-
lar filtration rate (GFR) can be used to
calculate a safe dose of contrast medi-
um [twice the GFR (in ml) is a safe
dose; maximum to be used is four times
the GFR]. Strategies to prevent contrast
nephropathy: withdraw nephrotoxic drugs
(NSAIDS, aminoglycosides, etc), stop
diuretics 48 hours before the procedure,
volume expansion over 12 hours pre-
procedure with normal saline, limit the
dose of contrast, use iso-osmolar contrast,
not high osmolar. Bicarbonate and
N-acetyl cysteine usage is of uncertain
benefit but can be used, and even diluting
the contrast medium. Doctors need to be
aware and vigilant for this condition.
Modern approach to anticoagu-
lant and antithrombotic therapy
Dr Darryl Smith
Clopidogrel has been tried and tested in
millions of patients with acute coronary
syndromes over the last 10 years and the
clinical relevance of genetically based
clopidogrelnon-respondersisnotclinically
significant, except in patients at high
risk of stent thrombosis. This pragmatic
view, presented by Dr Darryl Smith
(Johannesburg), did however carry the
caveat of using the newer agents, prasugrel
or ticagelor, in specific patient groups.
‘Prasugrel could well be the drug of
choice in younger patients at higher risk
of thrombotic events, also in diabetic and
STEMI patients, and in those with stents
and a history of recurrent events. Caution
is however required when considering
the use of prasugrel in patients with prior
cerebrovascular events or transient ischae-
mic events, those older than 75 years and
those with a low body weight of less than
60 kg. Prasugrel in the TRITON-TIMI 38
trial was more effective than clopidogrel
in reducing cardiovascular events but at a
slightly higher bleeding risk’,
6
he noted.
Ticagrelor, not yet available in South
Africa, is a very effective drug. It is not
a prodrug and its action is both of shorter
duration and reversible. ‘It does however
cause dyspnoea and bradycardia, which
restricts its use in patients with this cardi-
ac symptom’, Dr Smith added.
‘We also need to note that there
were significant mortality benefits with
ticagrelor in the PLATO study, achieved
with a minimal increase in bleeding.’ Dr
Smith noted that while aspirin remains the
cornerstone of anti-thrombotic therapy,
the newer agents such as clopidogrel,
prasugrel or ticagrelor should be used
in addition to aspirin to reduce platelet
aggregation.
Aspirin should be continued as antithrom-
botic therapy in high-risk patients under-
going surgery when clopidogrel is discon-
tinued – Dr Darryl Smith
‘The field of anti-coagulation is excep-
tionally difficult to review in a brief
presentation’, Dr Smith said. However,
it is generally accepted that greater anti-
coagulation efficacy comes at the price of
increased bleeding. ‘This generalisation
has been disproved by the ARISTOTLE
7
trial of apixaban in atrial fibrillation (AF),
which achieved a significant reduction in
stroke and systemic embolism without an
increased bleeding risk. This may well be
the shape of things to come: more effec-
tive protection from coagulation-related
events by agents that are also safer to use’,
he added.
‘Warfarin is extremely effective but it
is difficult to use, particularly in the frail
elderly who are at high risk of AF-related
stroke or systemic embolism. Registraries
show that less than 55% of these patients
are put on warfarin, because of concerns
around bleeding’, Dr Smith noted.
‘In the prevention of AF-related
events, the use of the CHA
2
DS
2
-VASc to
define risk of an embolic event, and the
HASBLED score to define risk of bleed-
ing, can help to individualise therapies
using the three new agents, dabigatran,
rivaroxaban and apixaban’, Dr Smith
argued. Use of these agents as front-line
therapy for the prevention of AF-related
vascular events is currently under vigor-
ous debate.
8,9
Complicating the use of these agents
is the differing doses required for the
same agent in different conditions. For
example, rivaroxaban in acute coronary
syndromes was trialed at 2.5 mg bid
versus 5 mg bid, but the recommended
dose for atrial fibrillation patients is 20
mg daily. This is also true for dabigatran,
which has a different dose in knee- and
hip-replacement surgery compared to
its dosage in the prevention of vascular
complications of AF.
Finally a lack of head-to-head studies
makes the clinician’s task of therapeutic
selection more difficult. These drugs offer
a great deal of promise, as shown in the
AF clinical trials against well-controlled
warfarin (some three to six patients saved
per 1 000), which could be even larger in
the real world of poor warfarin control’,
Dr Smith concluded.
The incretins: so much attention
at international meetings that a
review in South Africa is timeous
Dr Larry Distiller
Dr Distiller, co-ordinator of this special-
ist meeting, set the pace in a thorough
review of topics presented at the meet-
ing by cautioning clinicians to evaluate
incretin usage critically. ‘It is clearly time
to review these agents, both the GLP-1
agonists and the DPP-4 inhibitors as
their international status grows and they
become more available on the South
