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Indications
- In absence of contraindications consider thrombolysis for patients with:
- at least 30 mins of chest pain
- acute onset of at least 1 mm ST elevation in 2
adjacent limb leads or at least 1- 2 mm ST elevation
in 2 adjacent precordial leads or complete BBB
- time limits: should be administered to most patients presenting within 6 h
of pain, many patients presenting between 7-12 h (LATE showed 25.6%
reduction in mortality at 35 days after tPA given 7-12 h after pain onset).
Patients presenting >12 h from onset of pain should not routinely receive
thrombolysis. Within these time limits earlier thrombolysis associated with
a greater reduction in mortality.
- absolute contraindications:
- aortic dissection
- acute pericarditis
- active
bleeding
- cerebral haemorrhage or known intracerebral vascular disease
- relative:
- GI or GU haemorrhage within past 6 months
- stroke within past 6
months
- major surgery
- organ biopsy
- non-compressible vessel puncture within
past 2-4 weeks
- prolonged CPR with chest trauma or remaining unconscious
- diabetic proliferative retinopathy
- severe uncontrolled hypertension (SBP>200
or DBP>120)
- history of bleeding diathesis or hepatic dysfunction or
cancer
- pregnancy
- not
recommended in unstable angina / non-STEMI
- does not improve mortality or cardiovascular
events and may worsen outcome (increased bleeding complications; increased
bleeding within a ruptured atherosclerotic plaque may reduce blood flow and
enhance clot formation).
- lack of benefit may be related to thrombus
composition. In infarction it is fibrin rich, in UA the thrombus is
platelet-rich; the latter may be less responsive to the effect of fibrinolytic
agents.
Which thrombolytic?
- tPA over 90 mins followed by intravenous heparin
- Associated with lower mortality than treatment with
streptokinase (7%) (patients treated within 6 hrs)
- Results suggest that this
regimen would save 10 additional lives per 1000 patients treated but at the cost
of a higher risk of in-hospital intracranial haemorrhage (3 per 1000)
-
Sub-group analysis suggest that benefit is greatest in those at greatest risk ie
anterior AMI, presentation within 6 h, age 55-75 yrs
- Also consider tPA for patients previously treated with streptokinase.
Dosage regimens
- Streptokinase 1.5 MU over 1 h
- t-PA 15 mg/kg bolus followed by 0.75 mg/kg (max 50 mg) over 30 mins,
followed by 0.5 mg/kg (max 35 mg) over 60 min. Total dose not to exceed 100
mg; total infusion duration 90 min.
Bleeding complications
- small no. of patients require transfusion of clotting factors. Fibrinogen
depletion is most marked 3-5 h after thrombolytic therapy and cryoprecipitate is
likely to be of benefit (usual dose 10 units, repeated if necessary)
- aprotonin can be used to reverse the effect of streptokinase but this may
precipitate coronary re-thrombosis
- thrombolysis induced intracranial haemorrhage is associated with a 50%
mortality. Another 25% are severely disabled. NB overall incidence of stroke is
not increased by thrombolysis due to decrease in thrombotic and embolic strokes
Combination with other treatments
- combination with aspirin decreases mortality
- the addition of glycoprotein IIb/IIIa inhibitors or anti-thrombin agent
(bivalirudin) does not improve outcome
- addition of thrombolytic therapy to percutaneous coronary intervention
does not reduce infarct size but increases bleeding
Further reading
Fox KAA. Management of acute coronary syndromes: an update. Heart,
2004;90:698-706
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