“We have never seen such a slam-dunk effect as there was in INTERACT4,” Dr. Anderson said. “Not only did we show that early reduction of blood pressure in hemorrhagic stroke patients improved functional outcome, it also reduced bleeding in the brain, improved survival and quality of life, and reduced surgery and infection complications. That’s quite remarkable.”
The findings offer “clear evidence that for patients with hemorrhagic stroke, we must get the blood pressure under control as soon as possible and introduce systems of care to ensure this happens,” he added.
The reason for the clear findings in the current trial is probably the treatment time, Dr. Anderson said.
“This is the first trial in which blood pressure has been controlled in the ambulance and occurred much earlier than in the previous trials.”
Challenging Ischemic Stroke Guidelines
The INTERACT4 results in ischemic stroke patients are likely to be more controversial.
“Our results are clearly challenging longstanding beliefs around blood pressure control in ischemic stroke prior to thrombolysis,” Dr. Anderson said.
Current guidelines recommend a blood pressure < 185 mm Hg systolic before initiation of thrombolysis because of concerns about intracerebral hemorrhage, he noted. Often, blood pressure is lowered rapidly down to much lower levels in order give thrombolysis quickly.
“Our results suggest this may not be a good idea,” Dr. Anderson said. “I think these data will shake us up a bit and make us more cautious about reducing blood pressure in these patients. Personally, I wouldn’t touch the blood pressure at all in ischemic stroke patients after these results.”
He said the mechanisms behind the different stroke types would explain the results.
“If a patient is bleeding, it makes sense that higher blood pressure would make that worse,” Dr. Anderson said. “But when a patient has a blocked artery and ischemia in the brain, it seems likely that the extra pressure is needed to keep oxygen delivery to the ischemic tissue.”
Accurate Diagnosis Necessary
Because it is not possible to make an accurate diagnosis between ischemic and hemorrhagic stroke without a CT scan, Dr. Anderson stressed that at the present time, no action on blood pressure can be taken in the ambulance.
“There is a lot of interest in developing a lightweight brain scanner to be used in ambulances, but this won’t be routinely available for several years,” he said. “So for now, quick diagnosis of the type of stroke that is occurring on the patient’s arrival at the emergency department and, for hemorrhagic stroke patients, swift action to control blood pressure at this point is critical to preserving brain function.”
Commenting on the INTERACT4 results at the ESOC meeting, Simona Sacco, MD, professor of neurology at the University of L’Aquila, Italy, said this was a very important trial that would impact clinical practice.
“The data really reinforce that hemorrhagic stroke patients must have their blood pressure reduced as soon as possible,” she stated.
Dr. Sacco said the trial emphasizes the need to be able to distinguish between a hemorrhagic and ischemic stroke in a prehospital setting and supports the introduction of more mobile stroke units carrying CT scanners and calls for the development of biomarkers that can allow rapid differentiation between the two conditions.
In an accompanying editorial, Jonathan Edlow, MD, Department of Emergency Medicine, Beth Israel Deaconess Medical Center, Boston, points out several aspects of the trial that may potentially limit the generalizability of the findings. These include use of urapidil as the antihypertensive agent, which is unavailable in the United States; all patients being of Han Chinese ethnicity; and an unusually high sensitivity of initial CT scans in detecting visible signs of ischemia or infarction in patients in acute ischemic stroke.
“These findings should be considered hypothesis-generating, and they make the case for validation of the trial results in other settings,” Dr. Edlow wrote.
The INTERACT4 trial was funded by the National Health and Medical Research Council of Australia, the George Institute for Global Health, several Chinese healthcare institutions, and Takeda Pharmaceuticals China. Disclosures for study and editorial authors are provided in the original articles.
A version of this article appeared on Medscape.com.