Is it safe to treat high blood pressure after a stroke?

This study compared blood pressure levels measured before and after the onset of different types of stroke. 

A stroke is a disturbance of blood supply to a part of the brain. This can be caused by a blood clot in the brain (ischemic stroke) or a burst blood vessel (hemorrhagic stroke). Both types of stroke result in a lack of oxygen and nutrients reaching the brain tissue, causing cell death. High blood pressure, which is a measurement of how forcefully blood flows through arteries, is commonly linked to stroke. High blood pressure can damage or weaken blood vessels, increasing the risk of blood vessels rupturing and leading to a hemorrhagic stroke. High blood pressure is seen in about 75% of stroke victims, right after stroke occurrence. However, reducing blood pressure after stroke has been shown to be either of no benefit or of slight harm in trials of ischemic stroke, but to be of some benefit in trials of hemorrhagic stroke.

This study compared blood pressure levels in both ischemic and hemorrhagic stroke victims, before and after the stroke occurrence in order to see if there is a rationale behind the different risks and benefits of blood pressure-lowering treatment in these two disorders.  

Blood pressure, before and after stroke, was recorded in 636 individuals. Premorbid (before stroke) blood pressure was measured on average 17 times for each patient for around 10 years, and measured within 24 hours after stroke.

The study found that in patients with hemorrhagic stroke, blood pressure was greatly increased after stroke compared with usual levels before stroke occurrence. This increase included a rise in blood pressure for a short period (days or weeks) before the stroke event. On the other hand, patients with major ischemic stroke had similar and consistently high blood pressure levels both before and after stroke.

This suggests that patients who suffer from an ischemic stroke experience consistently high blood pressure – blood pressure that they may have become accustomed to. In accustomed hypertension (high blood pressure, lowering blood pressure rapidly with drugs could compromise blood flow as their body is used to pumping blood under high pressure. Therefore, the absence of benefit and the possible harm associated with blood pressure-lowering treatment in ischemic stroke might be related to reduction of blood pressure to a level at which a patient is not used to. 

Lowering blood pressure after hemorrhagic stroke may improve patient outcome whereas lowering blood pressure after ischemic stroke may have no effect or worsen symptoms. Hence maintaining normal blood pressure not only reduces the risk of stroke but also prevents the body from becoming accustomed to high blood pressure, which may have negative consequences when being treated for high blood pressure after stroke.

Firstly, unreported post-stroke use of blood pressure lowering drugs might have affected the results. Secondly, patients with minor stroke were excluded from the study so the results may not be generalized for all types of stroke.

Having regular blood pressure check-ups and maintaining normal blood pressure levels is very important in reducing the risk of stroke and subsequent complications of post-stroke treatment.