Blood pressure is the force exerted by circulating blood against artery walls. Maintaining a healthy range is fundamental to preventing long-term cardiovascular damage. Persistently high blood pressure strains and damages blood vessels, significantly increasing the risk for severe health events, including stroke. Understanding blood pressure measurements is a proactive step in protecting against these complications.
Defining Blood Pressure Readings
A blood pressure reading consists of two numbers, measured in millimeters of mercury (mm Hg). The top number, systolic pressure, reflects the pressure inside arteries when the heart contracts and pushes blood out. The lower number, diastolic pressure, measures the pressure in the arteries when the heart rests between beats.
Medical guidelines classify a normal reading as less than 120 mm Hg systolic and less than 80 mm Hg diastolic. A reading is considered elevated when the systolic number rises to 120–129 mm Hg while the diastolic remains below 80 mm Hg. Stage 1 hypertension is diagnosed when the systolic pressure is 130–139 mm Hg or the diastolic pressure is 80–89 mm Hg. Stage 2 hypertension is defined by a systolic reading of 140 mm Hg or higher, or a diastolic reading of 90 mm Hg or higher.
The Threshold for Hypertensive Crisis
The threshold for a hypertensive crisis defines a blood pressure level that poses an immediate threat of stroke. This occurs when the blood pressure reaches 180 mm Hg or higher (systolic) or 120 mm Hg or higher (diastolic). The situation is classified into two categories based on the presence of physical symptoms.
A hypertensive urgency is diagnosed when the pressure is 180/120 mm Hg or higher, but the patient exhibits no signs of acute organ damage. This requires prompt medical attention and medication adjustment but typically does not necessitate an emergency room visit.
A hypertensive emergency is defined by the same severely high blood pressure combined with evidence of acute organ damage. Damage to organs like the brain, heart, or kidneys elevates the situation to a true medical emergency. This high pressure actively causes life-threatening events, such as a stroke. Immediate hospitalization and rapid, controlled reduction of blood pressure are required to prevent permanent damage or death.
Symptoms Requiring Immediate Medical Attention
A person experiencing a hypertensive emergency often exhibits specific physical signs of acute organ damage. These symptoms signal that the force of the blood is actively harming the body and require an immediate emergency services call. A sudden, severe headache that feels different from a normal headache is a frequent warning sign.
Neurological symptoms include acute confusion, difficulty speaking, or a sudden change in vision, such as blurriness or temporary loss of sight. Physical signs of damage to other organs, like the heart or lungs, can manifest as chest pain, shortness of breath, or back pain. Signs related to an impending or active stroke, such as sudden numbness or weakness on one side of the body, demand immediate emergency care.
How High Blood Pressure Leads to Stroke
Extreme blood pressure damages the delicate blood vessels supplying the brain. The constant, excessive force causes arteries to thicken and stiffen over time, laying the groundwork for the two main types of stroke.
Ischemic Stroke
In an ischemic stroke, high pressure leads to the build-up of fatty deposits (plaque) within the artery walls. This plaque can narrow the vessel until blood flow stops or rupture, forming a blood clot that blocks a smaller artery in the brain. This blockage starves brain tissue of oxygen, causing cell death.
Hemorrhagic Stroke
A hemorrhagic stroke occurs when the pressure on weakened blood vessels becomes too intense. High blood pressure can cause a weakened artery wall to balloon out or burst entirely, leading to bleeding directly into the brain tissue. This bleeding deprives downstream tissue of blood and causes physical damage and swelling from the pooling blood, which can be rapidly fatal.