Blood pressure is the force exerted against artery walls as blood circulates. When this force becomes consistently elevated, it can lead to various health complications, including a heightened risk of stroke. Understanding the relationship between blood pressure levels and stroke is important for recognizing potential dangers and taking appropriate preventative measures.
Understanding Blood Pressure Readings
Blood pressure measurements consist of two numbers: systolic and diastolic. The systolic pressure, the top number, indicates the force of blood against artery walls when the heart beats and pumps blood out. The diastolic pressure, the bottom number, measures this force when the heart rests between beats. Both numbers provide valuable information about cardiovascular health.
An ideal blood pressure for most adults is typically less than 120/80 mm Hg. Blood pressure is considered “elevated” when the systolic reading is between 120-129 mm Hg and the diastolic is less than 80 mm Hg. High blood pressure, also known as hypertension, is categorized into stages.
Stage 1 hypertension is defined as a systolic pressure between 130-139 mm Hg or a diastolic pressure between 80-89 mm Hg. Stage 2 hypertension occurs when the systolic pressure is 140 mm Hg or higher, or the diastolic pressure is 90 mm Hg or higher. Many individuals with high blood pressure experience no symptoms, which is why it is often referred to as a “silent killer”.
The Critical Thresholds for Stroke Risk
Specific blood pressure levels significantly increase the risk of stroke, particularly those that indicate a hypertensive crisis. A hypertensive crisis is characterized by blood pressure readings of 180/120 mm Hg or higher. This severe elevation requires immediate attention due to the potential for organ damage.
A distinction is made between hypertensive urgency and hypertensive emergency. Hypertensive urgency involves blood pressure at 180/120 mm Hg or higher without signs of organ damage. While still serious and requiring prompt medical consultation, it does not present an immediate threat to organs. In contrast, a hypertensive emergency occurs when blood pressure reaches 180/120 mm Hg or higher and is accompanied by new or worsening symptoms indicating organ damage.
Symptoms of a hypertensive emergency can include a severe headache, blurred vision, chest pain, or shortness of breath. Other signs might be numbness, weakness, difficulty speaking, altered mental status, dizziness, seizures, or nausea and vomiting. Even sustained, lower levels of high blood pressure, such as Stage 2 hypertension (140/90 mm Hg or higher), greatly increase the long-term risk of stroke.
How High Blood Pressure Leads to Stroke
High blood pressure contributes to stroke by damaging blood vessels throughout the body, including those that supply the brain. The constant, excessive force against arterial walls can make them stiff, narrow, or prone to rupture over time. This damage sets the stage for different types of strokes.
One common mechanism is the development of atherosclerosis, a condition where high blood pressure accelerates the buildup of fatty material and plaque within the arteries. This plaque can narrow the arteries, reducing blood flow to the brain. If a piece of plaque breaks off or a blood clot forms on it, it can travel to the brain and block a blood vessel, leading to an ischemic stroke. Ischemic strokes account for the majority of all strokes.
High blood pressure also directly increases the risk of hemorrhagic stroke. This type of stroke occurs when a weakened blood vessel in the brain bursts and bleeds into or around the brain tissue. The intense pressure from uncontrolled hypertension can damage the vessel walls, making them more susceptible to rupture. High blood pressure is the most common cause of hemorrhagic stroke. Over time, persistent high blood pressure can also damage the tiny blood vessels deep within the brain, leading to small vessel disease, which further increases stroke risk and can impair cognitive function.
Immediate Action for Dangerously High Blood Pressure
Identifying dangerously high blood pressure readings requires prompt and appropriate action. If a blood pressure reading is 180/120 mm Hg or higher, it is considered a medical concern. If there are no accompanying symptoms, it is advisable to wait a few minutes and recheck the blood pressure. If the reading remains elevated, contacting a healthcare provider for urgent medical advice is important.
However, if a blood pressure reading of 180/120 mm Hg or higher is accompanied by symptoms, immediate emergency medical attention is necessary. These symptoms include a sudden severe headache, blurred vision, chest pain, or shortness of breath. Other warning signs that warrant calling emergency services include numbness or weakness, difficulty speaking, altered mental status, dizziness, or seizures. A medical professional can assess the situation and determine the appropriate course of action, which may involve emergency treatment to lower blood pressure and prevent further organ damage.