Stroke thrombolysis and thrombectomy: how clot-busting treatment works

The NHS describes a stroke as blood stopping flowing to a part of the brain. It can affect things like speech and movement and can take a long time to recover from. The most common type, according to the NHS, is an ischaemic stroke, caused by a blood clot blocking blood flow to the brain. Less commonly, a haemorrhagic stroke happens when a blood vessel bursts.

Because treatment for these two types is very different, the first priority in hospital is to find out which has occurred. That is why imaging comes first, and why clot-busting treatment is never given until bleeding in the brain has been ruled out. If you suspect a stroke you do not need to work out the type yourself: the action is the same, which is to call 999.

The NHS lists the main symptoms as face weakness (one side of the face may droop and it might be hard to smile), arm weakness (you may be unable to lift both arms and keep them there because of weakness or numbness in one arm), and speech problems (slurring or sounding confused). The word FAST stands for face, arms, speech and time to call 999.

Other signs include weakness or numbness down one side of the body, blurred vision or loss of sight in one or both eyes, difficulty speaking or finding words, confusion and memory loss, dizziness or falling over, a severe headache, and feeling or being sick.

The NHS says symptoms can sometimes stop after a short time and you may think you are fine, but you should still get medical help straight away. It advises calling 999 if you have had signs of a stroke within the last 24 hours even if they have now stopped, and not driving yourself to A&E. A transient ischaemic attack (TIA, or mini stroke), where symptoms last less than 24 hours, should be treated as urgent because without immediate attention you could be at risk of a full stroke.

Thrombolysis means a medicine given to dissolve a blood clot. The NHS lists it among treatments that may be given in the first 24 hours after a stroke, described as medicine to get rid of blood clots in the brain.

NICE guideline NG128 points clinicians to its technology appraisals for thrombolytic medicines (tenecteplase, TA990, and alteplase, TA264) for treating acute ischaemic stroke within 4.5 hours of symptom onset and when intracranial haemorrhage has been excluded. It also says they should be given only within a well-organised stroke service, with staff trained to deliver thrombolysis and monitor for complications, nursing staff trained in acute stroke, and immediate access to imaging and re-imaging with staff trained to interpret it.

NICE says appropriately trained and supported emergency department staff can give these medicines provided the person can then be managed within an acute stroke service with neuroradiological and stroke physician support. Protocols must also be in place for managing post-thrombolysis complications.

The pages read for this guide do not give figures for individual benefits or risks, which depend on the person. The stroke team will go through these with you or your family where they can, and decisions are made on the day using the scan and the history.

Thrombectomy is a procedure to remove a blood clot (the NHS describes it as surgery to remove a blood clot). It is mainly for clots blocking larger arteries supplying the brain, and it can be given in addition to thrombolysis.

NICE recommends offering thrombectomy as soon as possible and within 6 hours of symptom onset, together with intravenous thrombolysis if that is not contraindicated and within its licensed window, to people with acute ischaemic stroke and a confirmed blockage of a proximal artery in the front part of the brain circulation shown on CT or MR angiography.

For people who were last known to be well between 6 hours and 24 hours earlier (including wake-up strokes), NICE recommends offering thrombectomy where the same type of blockage is confirmed and imaging such as CT perfusion or diffusion-weighted MRI shows there is brain tissue that could be saved. It also says clinicians should consider thrombectomy for selected blockages in the back (posterior) circulation up to 24 hours.

Not everyone can have these treatments. NICE says the decision about thrombectomy takes into account the person's overall clinical status and the extent of established brain damage on the first scan, and that suitable people are selected as having a pre-stroke functional status of less than 3 on the modified Rankin scale and a score of more than 5 on the NIHSS stroke severity scale.

NICE advises immediate non-enhanced CT brain imaging for people with suspected acute stroke if, among other things, they are being considered for thrombolysis or thrombectomy, are on anticoagulant treatment, have a known bleeding tendency, or have a depressed level of consciousness. If thrombectomy might be indicated, CT contrast angiography follows, and CT perfusion imaging may be added if thrombectomy might be indicated beyond 6 hours.

If you are with someone who has had a stroke and they cannot speak, the NHS says you may be asked about their symptoms, which helps the team work out the type of stroke. Knowing the time the person was last well is one of the most useful things you can tell the ambulance crew.

NICE says everyone with suspected stroke should go directly to a specialist acute stroke unit. Other measures it describes include aspirin 300 mg as soon as possible and certainly within 24 hours once intracerebral haemorrhage has been excluded (given rectally or by tube if there is swallowing difficulty), continued daily until 2 weeks after onset when long-term antithrombotic treatment is started. Anticoagulation is not used routinely for acute stroke.

NICE also advises that supplemental oxygen is given only if oxygen saturation drops below 95%, and that blood glucose is kept between 4 and 11 mmol/litre. It does not recommend immediate statin initiation in acute stroke, though statins people already take should continue.

The NHS says medicines given long term may include anticoagulants to stop blood clots forming, medicines to lower blood pressure and statins to lower cholesterol. In hospital, a healthcare team of doctors, specialists and therapists helps start your recovery.

Emergency stroke treatment in the UK is delivered through the 999 and hospital stroke pathway, so there is no practical private route for the first hours. A person is taken by ambulance to a hospital with a hyperacute stroke service, and thrombolysis or thrombectomy decisions are made by the stroke team there.

Private care becomes relevant later, mostly for rehabilitation or further assessment, and depends on individual circumstances. Whichever route you use, the principle is the same: the sooner a person arrives at hospital after symptom onset, the more treatment options are open to them.