How to Prevent a Stroke

The good news is that most strokes are preventable.

Dr Michael Lim, cardiologist at Mount Elizabeth Hospital, talks about the importance of stroke prevention by managing associated heart disease and controlling risk factors such as high blood pressure, diabetes, high cholesterol and smoking.

Preventing stroke in those who have never had stroke is called 'primary prevention' while stroke prevention in people who have previously had a stroke is called 'secondary prevention'.

Stroke risk in people with atrial fibrillation

If you feel your heart 'fluttering' or have bouts of breathlessness, do not pass it off as anxiety. It may signal a potentially life threatening condition. 

Atrial fibrillation (AF), an abnormal heart rhythm which increases the risk of blood clot formation in the heart, is a major cause of stroke.

In those above age 60, about 1 in 10 will develop AF. However, AF can also occur in younger people, especially those with excessively high thyroid hormones.

In AF, the upper heart chamber (atrium) is 'quivering' at a heart rate of 400 per minute and hence the blood flow slows down considerably upon entering the atrium. Blood clots may form, and may then travel towards the brain and block the brain artery, triggering a stroke.

If the AF cannot be reverted to a normal heart rhythm, most patients will require the use of blood thinning medication to prevent blood clot formation.

Converting the AF to a normal heart rhythm is the best option to prevent a stroke. If that fails, blood thinning medication is often required. 

For secondary prevention, data from the "Risk of early stroke recurrence in patients with atrial fibrillation" study showed that the optimal time for commencement of blood thinning medication for preventing stroke recurrence is 4 – 14 days from the start of the stroke.

Stroke risk in people with narrowed neck artery

Narrowing of the neck (carotid) artery accounts for 10 – 15% of all strokes. 

For stroke patients with more than 70% narrowing, surgery to remove the obstruction (carotid endarterectomy or CEA), or insertion of a mesh to open up the neck artery blockage via a small incision (carotid artery stenting or CAS), are the available options. 

Both CEA and CAS are not low risk procedures. Hence, a patient should consider carefully before undergoing a procedure if there are no symptoms.

Stroke causes in younger people 

For young patients who develop stroke, 25% occur due to a tear of the inner lining of the neck (carotid) artery. Blockage of the artery due to blood clot formation in the wall of the artery or more commonly, clot formation at the site of the tear which then travels to the brain, 

The small Cervical Artery Dissection in Stroke (CADISS) trial showed a 2% stroke rate at 3 months by treating the patients with blood thinning medications.

Management of associated heart disease and optimal control of risk factors such as high blood pressure (BP), diabetes, high cholesterol and smoking can give good outcomes.

Preventing a second stroke after the first

If you develop a stroke, your urgent priority is to avoid progression. There is a high risk of deterioration in the early period.

The highest risk for progression or recurrence of the stroke is in the first hours to days from initial stroke, with almost 7% risk at 48 hours and a 10% risk by 7 days.

Management of acute blood pressure changes is a key measure. 

Starting blood thinning medication such as low-dose aspirin is essential to prevent recurrent stroke. In 2013, the "Clopidogrel in High-Risk Patients with Acute Non-disabling Cerebrovascular Events" trial, showed that in Chinese patients, the combination of aspirin and another blood thinning drug, clopidogrel, was more effective than aspirin alone in reducing the risk of stroke in the first 90 days. Always ensure that there is no bleeding in the brain before aspirin and clopidogrel are given.

Summary – key steps to preventing stroke

The best way to manage stroke is to prevent it.

• Control high blood pressure, high cholesterol or diabetes, and stop smoking
• If you have palpitations, check for AF
• If you keep losing weight or feel breathless, check for excessive thyroid hormones to avoid AF
• If you have AF and are on blood thinning drugs, a thorough discussion is required before surgery
• If you have severe carotid artery blockage but have no symptoms, control your risk factors and check for underlying heart disease
• As CAS and CEA are not low risk procedures, you need to discuss the pros and cons of either procedure versus medication with your specialist before making a decision
• If you require long term blood thinning medication, you need to discuss with the specialist on the type of medication and measures to reduce the likelihood of bleeding
• If you have severe blockage of brain or neck arteries, excessive lowering of blood pressure may cause fainting attacks
• If you have persistent headaches, you may require a scan of your brain vessels to detect uncommon vascular abnormalities that can cause life threatening strokes such as arterial aneurysms or other vessel abnormalities