Stroke Treatment Time Window: Clot-Dissolving Injection Up to 9 Hours — and a KG Hospital Study of Up to 72 Hours

01. Stroke Is a Family Problem, Not Just a Patient's

Stroke — pakkavatham in Tamil — is one of the most disabling conditions in neurology. As Dr. Ramakrishnan explains, the patient is not the only one affected. When a 40- or 50-year-old has a stroke, they may be unable to return to work, and a family member often has to stay with them full time. That is why treating a stroke quickly, while brain tissue can still be saved, matters so much.

Most strokes are ischaemic: a clot blocks an artery and part of the brain is starved of blood and oxygen. The longer the blockage lasts, the more brain tissue is lost. Opening the artery — with medicine, a procedure, or both — is the main aim of emergency stroke treatment at KG Hospital's Advanced Stroke Centre.

02. What Is IV Thrombolysis (the Clot-Dissolving Injection)?

Intravenous (IV) thrombolysis is a medicine given through a vein that dissolves the clot blocking the brain artery. The drugs used are alteplase or tenecteplase. Before the injection, a CT or MRI scan confirms that the stroke is caused by a clot and not by bleeding, because thrombolysis must never be given for a bleeding (haemorrhagic) stroke.

For a large blocked artery, the injection may be combined with mechanical thrombectomy, in which the clot is removed with a catheter in the neuro cath lab. Both are available round the clock at KG Hospital.

03. How Long After a Stroke Can the Injection Be Given?

Speed remains the most important factor: the earlier the treatment, the better the chance of recovery. But the time window has widened as brain imaging has improved.

The 9-hour window is based on trials such as EXTEND, in which patients selected by perfusion imaging and treated between 4.5 and 9 hours had better recovery (35.4% with little or no disability at 90 days, compared with 29.5% without treatment). The 2026 AHA/ASA guideline states that thrombolysis may be reasonable for these selected patients.

04. KG Hospital's Study: Thrombolysis Up to 72 Hours

Dr. Ramakrishnan explains that KG Hospital is now conducting a study in which thrombolysis may be given up to 72 hours after a stroke — but only for eligible patients. When a patient arrives within 72 hours, the team performs a scan with perfusion imaging. If the scan shows the patient fulfils the study criteria, the injection can be given, and there is a chance the patient will benefit.

Research into later treatment is active worldwide. The TRACE-III trial, for example, found that tenecteplase given between 4.5 and 24 hours helped selected patients with a large blocked artery who could not have thrombectomy, when perfusion imaging showed savable brain tissue.

The idea is simple: in some people, collateral blood vessels keep part of the brain alive for much longer than usual. Perfusion imaging can find these patients, instead of relying on the clock alone.

05. What Is Perfusion Imaging?

Perfusion imaging is a special CT or MRI scan that shows how blood is flowing through different parts of the brain. Software compares the core — tissue that has already died — with the penumbra, tissue that is short of blood but can still be saved. A large penumbra and a small core suggest that opening the artery can still help, even when the stroke started many hours earlier.

06. Is the Clot-Dissolving Injection Safe?

The main risk is bleeding, including bleeding into the brain. In the EXTEND trial, symptomatic brain bleeding occurred in 6.2% of treated patients versus 0.9% of untreated patients — yet more treated patients recovered well overall. Every patient is checked for conditions that raise the risk (such as recent surgery, blood-thinning medicines or very high blood pressure) and is monitored closely in the Stroke Unit and critical care after the injection.

07. Recognise a Stroke: BE-FAST

If you notice any of these signs, note the time the person was last seen normal and call for help at once. Do not wait for symptoms to settle and do not give food, water or tablets. Go straight to a stroke-ready hospital — KG Hospital's 24/7 Emergency activates its Code Stroke team on arrival.

08. Video Transcript (English)

1. Hello, I am Dr. Ramakrishnan, Neurologist, speaking from KG Hospital.
2. Stroke (paralysis) is a disease that can cause major problems in neurology.
3. It is not only the patient who is affected — their family is affected too.
4. Now, if a 40- or 50-year-old has a stroke, they cannot work, and someone has to stay with them all the time to look after them.
5. So when a stroke happens, we normally give an injection to dissolve the clot — intravenous (IV) thrombolysis.
6. As per this year's recommendation, we can give the injection up to 9 hours.
7. But we are now doing a study in which thrombolysis can be done up to 72 hours, if the patient is eligible.
8. If they come within 72 hours, we do a scan with perfusion imaging, and if they fulfil the criteria on the scan, we can give them the injection.
9. So when it is done this way, if they are eligible and we thrombolyse them, there is a chance that they will benefit from it.

Read the original Tamil transcript

வணக்கம், நான் டாக்டர் ராமகிருஷ்ணன், நியூராலஜிஸ்ட், கே.ஜி. ஹாஸ்பிடல்ல இருந்து பேசுறேன். பக்கவாதம் அப்படிங்கிறது வந்து ஒரு நியூராலஜில பெரிய பிராப்ளம் பண்ணக்கூடிய ஒரு வியாதி. பேஷண்ட் மட்டும் அதனால பாதிக்கப்படுறதில்ல, அவங்களோட குடும்பமும் அதனால அஃபெக்ட் பண்ணுவாங்க. இப்ப ஒரு 40 வயசு, 50 வயசுக்காரருக்கு ஸ்ட்ரோக் வந்தா, வேலை செய்ய முடியாது. அவரை பாத்துக்கறதுக்கு ஒருத்தங்க கூடயே இருக்க வேண்டியது இருக்கும். அப்ப ஸ்ட்ரோக் வந்ததுன்னா நார்மலா நம்ம இன்ஜெக்ஷன் போட்டு கரைக்கிறதுன்னு பண்ணுவோம் — Intravenous (IV) Thrombolysis. அது இந்த வருஷம் ரெக்கமண்டேஷன் படி 9 Hours வரைக்கும் நம்ம இன்ஜெக்ஷன் போடலாம். பட் நம்ம இப்போ ஸ்டடி ஒன்னு பண்றோம், அதுல வந்து up to 72 Hours த்ராம்போலைஸ் பண்ண முடியும், அது எலிஜிபிள் பேஷண்ட் இருந்தா. 72 Hours குள்ளார வந்தா, நம்ம ஸ்கேன் பண்ணி Perfusion Imaging இருக்கு, அது பண்ணி ஸ்கேன்ல அவங்க அந்த (criteria) ஃபுல்ஃபில் ஆனாங்கன்னா அவங்களுக்கு நம்ம இன்ஜெக்ஷன் போட முடியும். சோ அதுமாதிரி பண்ணும்போது அது எலிஜிபிளா இருந்து த்ராம்போலைஸ் பண்ணா அவங்களுக்கு இதனால பெனிஃபிட் கிடைக்கிறதுக்கு வாய்ப்பு இருக்கு.