Written or medically reviewed by a board-certified physician. See About.com's Medical Review Policy.

Updated October 12, 2014.

There are two main types of stroke: ischemic and hemorrhagic.  The first is more common, and results from a blocked artery to the brain. The second results from an arterial rupture, leading to blood spilling out into brain tissue. 

High blood pressure (hypertension) can lead to either type of stroke.  The management of these two types of strokes are very different, however, including blood pressure management after the stroke has occurred.


Blood Pressure and Intracranial Hemorrhage

Bleeding in the brain is known as intracranial hemorrhage (ICH).  The most common cause of ICH,  other than trauma, is poorly controlled blood pressure.  Whereas hypertension can predispose to ischemic stroke slowly by building up the arterial walls (and thereby narrowing them and making them easier to block), high blood pressure predisposes to intracranial hemorrhage in a more direct fashion.  The high pressure pushes the blood through weak spots in the brain’s blood vessels, such as where small arteries branch off the middle cerebral artery near the center of the brain, or where amyloid has built up in the vessels and made them more fragile.

This high blood pressure is usually due to someone paying insufficient attention to their health, but is also occasionally permitted by doctors.  In the days immediately following ischemic stroke, doctors often use a strategy called permissive hypertension to encourage blood flow through narrow arteries. This involves withholding most blood pressure medications the patient would normally take.

  While permissive hypertension is generally advisable, the strategy is not without risk. In the days following stroke, dead brain tissue becomes increasingly fragile. The blood that flows through this area may push through the weakened vessel walls.

Managing Blood Pressure After ICH

Despite the direct nature of blood pressure’s connection to bleeding in the brain, the management of blood pressure after ICH remains somewhat controversial.  Reducing blood pressure reduces the spread of blood into the brain, thereby reducing the risk of neurologic injury and death. But the pressure around intracerebral bleeds also reduces blood flow to surrounding tissue, causing secondary ischemic damage due to too little blood flow.  Reducing the blood pressure too much might worsen that ischemia.

Guidelines have tried to find some middle ground in the management of blood pressure in ICH by not permitting blood pressure to be as high as allowed in ishemic stroke, but also higher than normally recommended.  About 180 mmHg systolic has been a longstanding guideline.

The INTERACT-2 trial, published in the New England Journal of Medicine in 2013, used a more intense blood pressure goal of less than 140 mmHg, looking at death and disability after 90 days.  What they found was that there was no change in either death or disability, but functional outcomes seemed to improve, and there was far less hematoma expansion.  As a result, some academic centers are starting to use lower blood pressure goals for patients immediately after an intracranial hemorrhage.

Summary:

In short, high blood pressure predisposes to both types of stroke—ischemic and hemorrhagic. Shortly after a stroke, though, blood pressure may be kept higher than normally recommended, especially in ischemic stroke.  How the blood pressure is returned to normal remains an open question, though current widely used strategies may be overly gentle in returning blood pressure to normal limits.  In intracranial hemorrhage particularly, more aggressive blood pressure management is likely warranted.  

<sub>Sources:

CS Anderson,  E Heeley, Y Huang, J Wang, C Stapf, et al. for the INTERACT2 Investigators. Rapid Blood-Pressure Lowering in Patients with Acute Intracerebral Hemorrhage. N Engl J Med 2013; 368:2355-2365June 20, 2013DOI: 10.1056/NEJMoa1214609

AH Ropper, MA Samuels. Adams and Victor's Principles of Neurology, 9th ed: The McGraw-Hill Companies, Inc., 2009. McCabe MP, O'Connor EJ.</sub>