Health: Stroke

Introduction

Ischemic stroke is one of the most common life-threatening neurological diseases, affecting 15 million individuals worldwide annually. Unfortunately, one third of patients affected by Ischemic stroke die, making this disease the third leading cause of death globally. Another third of patients are permanently disabled, suffering from severe disability. Within 5 years of a stroke, more than half of the affected patients over forty-five years of age will die. Stroke incidence has declined by 40% over the last four decades in high-income countries, however its incidence has doubled in low-income countries. Age is one of the most important risk factors for stroke, and given the ageing world population a growing number will be at risk. Transient ischemic stroke (TIA) is a brief stroke, lasting only a few minutes. Symptoms of TIA are similar to stroke, and include weakness, numbness, or paralysis, speech difficulty, visual change, dizziness or loss of balance or coordination. It is essential to recognize a TIA attack and seek medical help immediately, because it significantly increases risk of subsequent stroke.

Prevention

Many stroke risk factors have been substantiated, including both modifiable and non-modifiable factors. An estimated 50% of strokes are preventable through adjustment of modifiable risk factors. Risk of stroke can be reduced by lowering blood pressure, weight loss, exercise, and treating conditions such as atrial fibrillation, hyperlipidemia, diabetes, and smoking addiction.

• Hypertension

It is the most important modifiable risk factor, contributing to 60% of all strokes. It increases risk of stroke through different mechanisms. These include promotion of plaque formation in major arteries that supply the brain, promotion of fragility of small brain arteries, as well as cardiac dysfunction and atrial fibrillation. Several studies have confirmed that there is a direct relationship between hypertension and incidence of stroke. For example, reducing diastolic blood pressure by an average of 5 to 6 mmHg over 5 years results in 42% reduction in stroke risk. In the HOPE study (Heart Outcome Prevention Evaluation), with 19 participating countries, 9297 patients were followed up for 4.5 years on ramipril 10 mg versus placebo. Even modest reduction in blood pressure was associated with major decrease in the rates of stroke (32%) and fatal stroke (61%).

•  Atrial Fibrillation

Atrial fibrillation is a cardiac condition that results in an irregular heart rhythm and blood clot formation. In Canada, approximately 350,000 people are affected. As people age there is an increased incidence of atrial fibrillation. Atrial fibrillation increases the risk of stroke 3 to 5 times, through formation of blood clots in heart chambers and subsequent dissemination to brain arteries. Most patients are prescribed Warfarin, a blood thinning agent, which reduces risk of stroke by 68%. It should be noted that there is a modest increase in risk of major bleeding in patients who take warfarin, 1.3% compared to 1% in those not taking warfarin.

•   Hyperlipidemia

Current practice guidelines include reduction in cholesterol levels as a measure of risk reduction, though the association between cholesterol and primary stroke prevention is not entirely clear based on multiple clinical trials. In secondary prevention of stroke, patients who have already been affected by TIA or stroke benefit from cholesterol lowering agents.

•   Diabetes Mellitus

Diabetes is a significant risk factor for stroke, as well as stroke-induced mortality and disability. Diabetes treatment including blood sugar management results in a 12% risk reduction, likely through protection of blood vessels that become fragile in diabetic patients. Nutrition and Supplements: Research is ongoing regarding the effects of nutrition on stroke prevention. High salt intake increases stroke risk by 23%. Dietary factors that have proven to reduce stroke risk include high intake of fish, vegetables and fruits, whole grains, tea, reduced-fat milk, dark chocolate. Daily supplementation with potassium reduces the risk of stroke by 11%. On the other hand, increased risk of stroke is associated with consumption of meat and sugary drinks.

Treatment

Initial systemic thrombolysis (administration of drugs to dissolve blood clots) within 4.5 hours of symptom onset is the standard of care. Therefore, “time is brain” and seeking immediate help is essential. Other medications include antiplatelet agents and blood thinners including aspirin and heparin. More advanced neuro-interventional techniques that are used in select patients include intra-arterial thrombolysis which involves the direct injection of clot busting medication into brain arteries. In patients with severely narrowed carotid arteries, balloon angioplasty and stenting or surgical removal of arterial plaques are indicated depending on patient criteria.