The enormous success of treating coronary thrombosis with thrombolytic therapy makes the treatment of ischaemic stroke the obvious next step. Several large trials have confirmed the benefits of thrombolysis in acute stroke within three hours of development of symptoms - eg, National Institute of Neurological Disorders and Stroke (NINDS) in the USA.
More recently concerns have been raised that thrombolysis may not be safe at 3-4.5 hours following an acute ischaemic stroke.This is despite a previous Cochrane review which recommended that thrombolysis was beneficial up to six hours following acute ischaemic stroke. At present the guidelines have not changed but further research is warranted.
- Haemorrhagic stroke has been excluded.
- The patient presents within four and a half hours of having the event.
- Access to specialised services is available.
- Stroke accounted for 11% of all deaths in 1999.
- The incidence rises with age, doubling every decade after the age of 45.
- Over two thirds of strokes occur in the those aged over 65.
- There is no age limit to the use of thrombolytic therapy.
- It is essential to have a CT or MRI scan to differentiate the type of stroke before commencing treatment. MRI is as accurate as CT to detect acute haemorrhage in patients with focal stroke symptoms and is more accurate than CT for the detection of chronic intracerebral haemorrhage.
- Access to these investigations must be available 24 hours a day. Interpreting the scan requires experience but it is possible to train people to an acceptable level of competence in a short time.
- Even if the window for thrombolysis has been missed, the Royal College of Physicians (RCP) states that all patients should have CT or MRI within 24 hours.
- An ECG is useful in diagnosing pericarditis and possible causes of stroke, including myocardial infarction and atrial fibrillation. An ECG is not required before starting alteplase.
The interpretation of a CT or MRI scan to exclude haemorrhage is not easy and usually requires a senior radiologist or an experienced geriatrician. It should not be delegated to a junior doctor in the small hours of the morning. The availability of such expertise 24 hours a day, seven days a week, adds further to the requirements of a stroke service.
- Alteplase should only be administered within a well-organised stroke service.
- Staff in such a service should be trained in delivering thrombolysis and in monitoring for any associated complications.
- Care should be provided by level 1 and 2 nursing staff trained in acute stroke and thrombolysis.
- There should be immediate access to imaging and re-imaging and staff appropriately trained to interpret the images.
- Protocols should be instituted for the delivery and management of thrombolysis, including post-thrombolysis complications.
- Staff in A&E departments, if appropriately trained and supported, can administer alteplase for the treatment of acute ischaemic stroke provided that patients can be managed within an acute stroke service with appropriate neuroradiological and stroke physician support.
- Every patient treated with alteplase should be started on aspirin 300 mg daily after 48 hours, unless contra-indicated. This should be continued for 14 days.
The situation is more complex for acute ischaemic stroke than for coronary thrombosis:
- Only 80% of strokes are ischaemic and giving thrombolysis for a haemorrhagic stroke would be disastrous.
- Stroke tends to be more gradual in onset and may even start during sleep. Hence, patients tend to present later.
- The window of opportunity for effective thrombolysis is four and a half hours from the onset of the stroke and, in that time, a firm diagnosis of ischaemic stroke must be made.
- As a result, only about 1-11% of patients fulfil the criteria.
Cochrane is uncertain as to whether lower doses of thrombolytics are safer or if there is any advantage to intra-arterial over intravenous routes of administration. Intra-arterial treatment tends to be used for posterior stroke but it is still uncertain if it is superior. The important point is early recovery of flow and the vertebrobasilar system appears to take longer to recover.
Contra-indications for thrombolytic treatment
The following suggest haemorrhagic stroke or other reasons to avoid thrombolysis:
- Seizure at onset of stroke.
- Symptoms suggestive of subarachnoid haemorrhage.
- Stroke or serious head injury in the preceding three months.
- Major surgery or serious trauma within two weeks.
- Previous intracranial haemorrhage.
- Intracranial neoplasm.
- Arteriovenous malformation or aneurysm.
- Gastrointestinal or urinary tract haemorrhage in the preceding three weeks.
- Lumbar puncture in the preceding week.
- Current anticoagulation (INR >1.7).
- Acute pericarditis.
- Neurological signs improving suggesting a TIA.
- Marked hypertension - systolic BP >185 mm Hg or diastolic BP >110 mm Hg, or need for aggressive antihypertensive therapy to reach below these levels.
- Platelets <100 x 109/L.
- INR >1.7.
- Glucose <2.7 mmol/L (50 mg/dL) or >22 mmol/L (400 mg/dL).
- Positive pregnancy test (very unusual in this group).
Blood should be sent for group and cross-match in case transfusion is required.
In the NINDS trials, the rate of clinical deterioration from new intracranial haemorrhage, 24 to 36 hours after treatment, was 6.4% with alteplase versus 0.6% with placebo. Mortality at three months was 17% in the alteplase group and 21% in the placebo group but did not reach statistical significance.
A good outcome 24 hours after thrombolysis tends to predict a good outcome at three months.
Three months after alteplase therapy:
- Approximately 30% of patients are neurologically normal or near normal.
- 30% have mild-to-moderate neurological deficits.
- 20% have moderate-to-severe neurological deficits.
- 20% have died.
Three months after alteplase therapy:
- Approximately 50% of patients are completely or almost completely independent in activities of daily living.
- 15% are moderately dependent on others.
- 15% are completely dependent on others.
- 20% have died.
Implications for primary care
Although the high technology of scanning and thrombolysis is delivered within a hospital system, there are still implications for primary care. The most obvious is that if there is reason to suspect a stroke, the patient must be admitted to a suitable unit with the utmost speed. Simply being in hospital within three hours is not good enough. The scan has to have been taken, read and the infusion started within three hours of the onset of symptoms. Hospitals also need to look to their systems to reduce delay, as has been done with acute myocardial infarction.Even if the deadline has passed, patients should still be admitted to hospital, as all should have a scan within 24 hours and the outcome for all is better in a stroke unit.
Any patient who presents with transient neurological symptoms suggestive of a cerebrovascular event should be considered to have had a TIA.
ABCD and ABCD-2 Score
It is calculated based on:
Age (≥60 years, 1 point). Blood pressure at presentation (≥140/90 mm Hg, 1 point). Clinical features (unilateral weakness, 2 points or speech disturbance without weakness, 1 point). Duration of symptoms (≥60 minutes, 2 points or 10-59 minutes, 1 point).
The calculation of ABCD-2 also includes the presence of diabetes (1 point).
Total scores range from 0 (low risk) to 7 (high risk).
- Patients who have had a suspected TIA with an ABCD-2 score of 4 or above and those presenting with crescendo TIA - that is, two or more TIAs in a week (even if the ABCD-2 score is 3 or below), are at high risk of stroke and should have specialist assessment and investigation within 24 hours of onset of symptoms.
- Patients who have had a suspected TIA who are at lower risk of stroke - that is, an ABCD-2 score of 3 or below and those who have had a TIA but who present late, ie more than one week after their last symptom has resolved, should have specialist assessment and investigation as soon as possible, but definitely within one week of onset of symptoms.
In addition to specialist assessment, both groups should also receive:
- Aspirin (300 mg daily) immediately.
- Measures for secondary prevention introduced as soon as the diagnosis is confirmed, including discussion of individual risk factors.
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