Læknablaðið : fylgirit - 01.06.1994, Side 13

LÆKNABLAÐIÐ/FYLGIRIT 25
11
TREATMENT OF MYOCARDIAL
INFARCTION: WHAT DO THE
TRIALS TELL US?
Peter Sleight MD DM FRCP
Field Marshal Alexander Professor of Cardiovascular Medicine,
University of Oxford, John Radcliffe Hospital, Oxford 0X3 9DU UK
Thrombolysis and
antithrombotic treatment
A unique collaboration of all triallists involved
in studies of a fibrinolytic agent against control
has given us individual patient data from the ap-
proximately 130,000 subjects randomised - over
99% of the trial data (Fibrinolytic Therapy Trial-
lists Collaboration) (1). From this large data base
we are now able to say with some confidence what
the benefits are for a large range of patients.
It is now quite clear that lytic therapy reduces
mortality in patients who present with ST eleva-
tion and bundle branch block (L or R) and with a
history suspicious of acute myocardial infarction
(AMI), up to 12 hours from the onset of the recent
symptoms. The reduction in mortality is better
with earlier treatment - a benefit of 33 ± 11/1000
fewer deaths at 5 weeks in patients treated in the
first hour, 23 ± 5 for hours 2-3 and thereafter
reducing to 20 ± 5 between 4-6 hours, but still a
useful 17 ± 6 between 7 and 12 hours (all values
highly significant). Curiously, patients with ST
segment depression (who have a high mortality of
c. 14%) do not seem to benefit, but the numbers
randomised are relatively small. In such patients I
record V1-V3R in order not to miss RV infarction
with ST segment elevation in R chest leads. Al-
though elderly patients benefit less in percentage
terms, they have a much higher absolute mortal-
ity and are therefore worth treating, given other-
wise good health. For other categories studied, by
sex, entry BP, heart rate, prior MI, diabetic, all
show benefit.
The risk of bleeding and haemorrhagic stroke
increases with increasing age and entry blood
pressure. This risk is less with SK than tPA, per-
haps because the former is hypotensive and pro-
tective. Front- loaded tPA (GUSTO) may have a
small (? 5-6/1000) benefit for patients treated very
early, compared with SK, but definitely increases
the risk of stroke by 3-4/1000.1 use it only in very
early and young patients with large AMI’s, and
for patients who have previously received SK or
APSAC.
Aspirin adds a benefit of about 20/1000, with no
time dependence. There is no place for routine
heparine with SK. IV Heparin is used with tPA,
but there is no adequate mortality data on which
to judge the risk /benefit of this when added to
aspirin.
The most important decision with regard to
thrombolysis is not which agent to use, but to use
any agent more widely and to use it promptly.
Too much delay occurs in hospitals due to poor
organisation.
Vasodilators post myocardial
infarction - ISIS-4
It is now abundantly clear from the CONSEN-
SUS-1, (2) the SAVE, (3) SOLVD, (4,5) and
AIRE (6) studies that the ACE inhibitors (ena-
lapril, captopril and ramipril) have a number of
beneficial effects in patients with left ventricular
damage. In these studies this damage was wholly
or mainly due to ischaemic heart disease. The
benefits were mainly by prevention of progres-
sion of left ventricular dilatation, and so reducing