Ischaemic stroke

• What is Ischaemic Stroke?
• Statistics
• Risk Factors
• Progression
• Symptoms
• Clinical Examination
• How is it Diagnosed
• Prognosis
• Treatment
• References

What is Ischaemic Stroke?

A stroke or cerebrovascular accident (CVA) occurs when a blood vessel that carries oxygen and nutrients to the brain is blocked by a clot (ischaemic stroke), or bursts and bleeds (haemorrhagic stroke). As a result, part of the brain cannot get sufficient blood (and hence cannot get enough oxygen and nutrients), and starts to die.Ischaemic stroke can be due to:

1. Thrombosis – local blockage of an artery as a result of disease in the blood vessel wall.
2. Embolism – particles of debris originating elsewhere block arteries supplying a particular part of the brain.
3. Systemic hypoperfusion – general inadequate blood supply that may affect the brain as well as the other organs.

Statistics

In the United States:

• The number of new or recurrent stroke cases is about 700,000 every year.
• On average, a stroke occurs every 45 seconds.
• Stroke is the third leading cause of death, killing about 157,000 people a year.
• Men are at a higher risk than women for stroke.
• In 2003, the stroke death rates per 100,000 population for specific groups were 51.9 for white males, 50.5 for white females, 78.8 for black males and 69.1 for black females.

In Australia:

• Stroke is also the third largest cause of death, and one of the leading causes of disability.
• There are over 48,000 new cases of stroke a year, with a stroke occurring every 11 minutes.
• At the current rate, this figure is predicted to reach 74,000 by the year 2017.
• One third of stroke patients die in the first 12 months.
• More than 50% of strokes occur in people under 75 years old, and 5% are under the age of 45.

In general, ischaemic stroke accounts for around 80% of all strokes, and haemorrhagic stroke makes up about 20%.

Risk Factors

Risk factors for ischaemic stroke include:

• Age (the risk doubles with every 10 years)
• High blood pressure
• High cholesterol
• Smoking
• Diabetes mellitus
• Heart disease
• Previous stroke
• Family history of stroke
• Atrial fibrillation (irregular heart rhythm)
• Transient ischaemic attacks (TIA) – warning strokes. Even though the symptoms disappear after a short time, TIAs are strong indicators of a possible major stroke.
• Thrombophilia (conditions that make the blood more prone to clotting, especially in young patients).

Progression

As mentioned earlier, ischaemic stroke can be due to thrombosis, embolism or systemic hypoperfusion.

Thrombotic stroke
Thrombotic strokes are those in which clot formation reduces blood flow, or a clot breaks off and travels to a later part of the blood vessel. Thrombotic strokes can be divided into large and small vessel disease. Thrombosis-related symptoms progress in a stepwise or stuttering fashion, with some periods of improvement.

Embolic stroke
Embolism (particles of travelling debris originating elsewhere) may be from the heart, the aorta or other large vessels. Symptoms often start suddenly and improve very quickly.

Systemic hypotension
Reduced blood flow is more global and does not affect isolated regions. Symptoms are more generalised and without a particular focus, in contrast to thrombosis and embolism.

Symptoms

Because other conditions (e.g. seizures, syncope, migraine, and low sugar level) may mimic an ischaemic stroke, the doctor will want to find out the following points from the patient/relative:

• Intake of insulin or oral medications for diabetes
• History of a seizure disorder or drug overdose
• Medications on admission
• Recent trauma
• Hysteria

The doctor will also find out about the pace and course of symptoms, risk factors (diabetes, high blood pressure, high cholesterol level, smoking, a strong family history, known heart diseases), previous transient ischaemic attacks (TIA) and activity at the time when symptoms began.
Stroke is associated with a sudden onset of neurological problems:

• Weakness or loss of function on one side of the body
• Impairment of sensation on one side of the body
• Speech difficulty
• Articulation difficulty
• Visual disturbance on one side
• Imbalance, nausea, dizziness, seeing double

Clinical assessment in most patients should be able to determine whether the stroke involves the vessels supplying the front (anterior) part of the brain (anterior circulation syndrome), back (posterior) of the brain (posterior circulation syndrome), or small vessels supplying a small part (lacunar syndrome).
Generally, anterior involvement causes weakness, sensory loss, visual defect and speech difficulty. Posterior involvement leads to imbalance, dizziness, and seeing double. A stroke involving a small vessel is associated with more focused clinical features (e.g. limited to only muscle weakness, or sensory defect, etc).

Clinical Examination

The doctor will examine the blood pressure, temperature, pulse rate, heart, eye, pulses in the neck, arms and legs, and also perform a full examination of the nervous system. Signs of injury to the head/neck will also be looked for.

How is it Diagnosed

Investigations of a stroke patient include:

• Brain computed tomography scan (CT): typical initial imaging study.
• Electrocardiogram (ECG) (heart tracing): to detect heart attack, irregular heart rhythm, enlargement of heart chambers that makes the heart more prone to clot formation
• Chest x-ray: if lung or heart disease is suspected.
• Blood tests: to check blood cells, clotting ability, cholesterol and fats level, kidney function, sugar level, markers for heart attack (if suspected), liver function, pregnancy status in women of child-bearing age, toxicology screen and blood alcohol level (in some patients).
• Ultrasound: of blood vessels in the neck (carotid artery Doppler) – to detect blockage or narrowing of the carotid arteries supplying the brain.
• Ultrasound of the heart (echocardiography).
• In young patients: investigations for conditions that make them more prone to clotting, holes in the heart, etc.

Prognosis

Of the 48,000 Australians diagnosed of a stroke each year, approximately 1/3 will die in 12 months, 1/3 will be permanently disabled, and 1/3 will progress past 12 months without permanent disability.

Treatment

Treatment of ischaemic stroke is according to the National Stroke Foundation Guidelines:

General treatment

• Admission to stroke unit is preferable.
• Thrombolysis: treatment to break clots within 3 hours of stroke.
• If CT scan excludes bleeding in the brain, aspirin is given as soon as possible after the beginning of stroke symptoms.
• The ability to swallow will be assessed. If the patient is deemed to be unable to swallow, a speech therapist will be involved. Alternative methods of feeding via a tube will be considered, with possible involvement of a dietitian.
• Physiotherapy referral for mobility and rehabilitation.
• Occupational therapy referral for optimisation of daily functioning.
• Psychosocial issues addressed by psychologist if needed. Stroke is a major risk to depression.

Management of complications of stroke

• Fever will be investigated for any source of infection.
• Prevention of clots in the leg veins with early mobilisation, stockings, and possibly heparin.
• Fall risk will be assessed, and shoulder pain and pressure sores prevented.

Prevention of future events

• Aspirin, or a combination of low dose aspirin and modified release dipyridamole, or clopidogrel, should be given to all patients with ischaemic stroke not prescribed warfarin.
• Carotid endarterectomy (removal of plaque or clots from the inner wall of the carotid artery in the neck) may be considered if there is significant narrowing or blockage of the artery.
• Warfarin may be considered in certain patients seven days after the onset of an ischaemic stroke.
• Blood pressure reduction.
• Cholesterol reduction with diet and medication.
• Lifestyle modification: smoking cessation, moderate alcohol consumption, weight reduction, low fat and high fibre diet, moderate exercise.

Discharge planning
 

• Liaising with general practitioner
• Post-discharge needs (physical, emotional and social)
• Equipment and adaptations
• Family meetings
• Provision of information

More information

For more information on how international trials are using CT scans to predict and improve stroke outcomes, please see Professor Lesley Cala’s video on Improving Stroke Outcomes.

 

References

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