Tissue plasminogen activator (tPA) is a naturally occurring protein in the body that activates plasmin, the main enzyme responsible for dissolving blood clots (fibrinolysis). In medical use, tPA refers to recombinant forms of this protein (such as alteplase, tenecteplase, and reteplase) that are administered as medicines to break down dangerous blood clots in emergencies.
tPA is used as a thrombolytic (clot-dissolving) treatment in two main emergency settings. In acute ischaemic stroke, intravenous alteplase is given within 4.5 hours of symptom onset to dissolve the clot blocking a cerebral artery and restore blood flow to the brain, significantly reducing disability if given quickly. In STEMI (heart attack), thrombolytics are given when primary PCI cannot be performed within an acceptable timeframe, typically where transfer to a primary PCI centre would take too long.
During cardiac arrest with suspected massive pulmonary embolism (where a large clot is blocking the pulmonary arteries), intravenous tPA may be given during or after CPR to dissolve the clot. CPR must be continued for at least 60 to 90 minutes after tPA administration to allow time for the drug to work. Systemic thrombolysis substantially increases bleeding risk, including the risk of intracranial haemorrhage.
The major risk of tPA is serious bleeding, including brain haemorrhage (which can be fatal or cause stroke). It is therefore contraindicated in patients who have had recent surgery, trauma, or intracranial bleeding. In stroke treatment, CT scan must confirm ischaemic rather than haemorrhagic stroke before tPA is administered.
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