Blood vessels connecting adjacent arterial trees regulate blood flow to the brain in affected patients stroke. Researchers at the University of Zurich have now shown that these vessels prevent brain hemorrhage after treatment to remove blood clots. They play a crucial role in the recovery of affected patients.
“These vascular bridges maintain brain autoregulation and allow for slower, more gradual reperfusion, which results in smaller infarcts,” says Wegener. There research was published in the journal Neuron.
The danger of ischemic strokes
Ischemic strokes represent a serious health burden. They occur when a blood vessel supplying the brain becomes blocked, affecting blood flow to the brain. As a result, the brain tissue suffers from a lack of oxygen and nutrients, which causes symptoms such as paralysis, confusion, dizziness, headaches, difficulty speaking or even death.
To treat these symptoms and restore blood flow to the brain, the blocked vessel must be “unclog” or recanalized. Contemporary treatments to remove the clot include intravenous thrombolysis or mechanical thrombectomy using a catheter. However, even with timely removal of the clot, many stroke patients do not fully recover.
The research group of Susanne Wegener, professor at the University of Zurich (UZH) and leading physician at the Department of Neurology at the University Hospital Zurich (USZ), has now shown that the outcome of stroke treatments depends on the collateral network. Collaterals are blood vessels that connect adjacent arterial trees, providing potential diversion networks in the event of vascular blockage.
For their study, the research team with the two co-first authors Nadine Binder and Mohamad El Amki used a mouse model of stroke and advanced in vivo imaging methods to study changes in arterial blood supply. In mice with poor collaterals, arterial segments were dysfunctional and stiff after clot removal. “The rapid reperfusion that followed caused a brain hemorrhage and increased mortality,” says Wegener.
The researchers were then able to confirm the results obtained in the mouse model in stroke patients. Stroke patients who had poor collaterals showed similarly rapid reperfusion after treatment to remove blood clots, even resulting in small brain hemorrhages and an unfavorable recovery.
So far, the focus has been on rapid removal of blood clots in stroke patients, while problems associated with rapid post-treatment reperfusion and its potential harmful effects have received little attention. The study now implies that it is possible to identify stroke patients with a higher risk of poor recovery based on the speed of reperfusion during treatment. “Future therapeutic interventions for stroke should aim to improve collateral function, allowing for beneficial reperfusion after stroke,” concludes Susanne Wegener.
Intense drop in blood pressure after clot removal worsens stroke recovery
A large stroke study showed that intensive lowering of blood pressure after clot removal worsens recovery. The results of the study, which was stopped early due to the importance of the results, were presented in an eleventh hour session at the World Stroke Congress and simultaneously published in The Lancet.
Professor Craig Anderson, director of Global Brain Health at the George Institute for Global Health, said the rapid onset of this effect suggests the more aggressive approach is compromising the return of blood flow to the affected area.
“Our study provides a strong indication that this increasingly common therapeutic strategy should now be avoided in clinical practice,” he said.
About 85% of strokes are ischemic strokes, caused by loss of blood flow to an area of the brain due to a blockage in a blood vessel, leading to a loss of neurological function.
Endovascular thrombectomy is an increasingly used nonsurgical treatment for ischemic stroke, in which microcatheters or thin tubes visible on X-rays are inserted into the blood clot to dissolve it.
“A potential drawback to this now widely used and effective treatment is that the rapid return of blood supply to an area that has been deprived of oxygen for a while can cause tissue damage known as reperfusion injury,” he said Professor Anderson.
“This has led to a shift in medical practice towards more intensive lowering of blood pressure after clot removal to try to minimize this harm, but without evidence to support the benefits versus the potential harms.”
To try to fill the evidence gap, the researchers recruited 816 adults with acute ischemic stroke who had elevated blood pressure after clot removal from 44 centers in China between July 2020 and March 2022. They had a
n average age of 67 years and just over a third were women. .
407 were assigned to the most intensive systolic blood pressure control (target <120 mm Hg) and 409 to the least intensive control (target 140-180 mm Hg), with the goal to be achieved within one hour of study entry and maintained for 72 hours.
The researchers examined how well patients in both groups recovered according to a standard measure of disability, ranging from 0-1 for a good outcome with no or no symptoms but no disability, scores of 2-5 indicating increasing levels of disability (and addiction). , and a score of 6 indicates death.
Patients in the more intensively treated group had significantly worse scores on the scale than those assigned to the less intensively treated group.
Compared to the less intensive group, they had earlier deterioration of brain tissue and greater disability at 90 days, but there were no significant differences in brain hemorrhages, mortality or serious adverse events.
Patients who had more intensive blood pressure control also rated their quality of life significantly worse due to limitations in their physical abilities resulting from the stroke.
Prof. Anderson said that after analyzing the medical literature, the research team could not find strong enough evidence to recommend the ideal target for blood pressure control after blood clot removal in ischemic stroke patients acute .
“While our study has now shown that intensive blood pressure control to a systolic target of less than 120 mm Hg is harmful, the optimal level of control has yet to be defined,” he said.
Children with severe strokes may fare better if treatment includes mechanical removal of the clot
According to a late preliminary study, the likelihood of severe disability occurring three months after a stroke was six times greater among children whose stroke caused by a clot in a large vessel (a type of ischemic stroke) had not been treated with a procedure to extract the clot. science presented today at the American Stroke Association's 2022 International Stroke Conference. The conference is a world-class meeting for researchers and clinicians dedicated to the science of stroke and brain health that will be held in person in New Orleans and virtually, February 9-11, 2022.
Although the risk of stroke increases with age, it can occur at any age.
This Australian study looked at severe strokes in children that occurred in a large artery or blood vessel in the brain. Treatment for these types of large vessel clots in adults may involve mechanical removal of the clot. In this procedure, also called endovascular therapy or mechanical thrombectomy, a tiny tube, or catheter, with a special clot retrieval device at the end is passed through a blood vessel to remove the clot.
Although mechanical removal of clots is known to improve stroke recovery in adults, children have not been included in previous research. This study compared post-stroke disability between children who received the procedure and those who did not, to explore whether mechanical clot removal could be beneficial for children after a severe stroke.
The study included 166 children (average age 6 years; 65% boys) treated for stroke at multiple hospitals in New South Wales, Australia, from 2010 to 2019. Just under a quarter of the children (39) had a vessel blockage large blood or a severe stroke, which is similar to the rate found in adults. Thirteen children with this type of stroke received mechanical blood clot removal, while 26 did not.
The 26 children who did not receive mechanical blood clot removal had greater physical disability than the other two groups: the 13 children who received mechanical thrombectomy and 127 children whose stroke was not caused by a blockage in a large vessel blood. Specifically, the researchers discovered:
Children with a large blood vessel blockage who did not receive blood clot removal were six times more likely to have moderate to severe disability after three months than those who received the procedure.
Compared with children with an ischemic stroke that was not in a large vessel, children with large blood vessel obstruction who had not undergone mechanical thrombectomy were more than 3.5 times more likely to have significantly worse outcomes three months after stroke.
“We were surprised by how common large vessel blockage is in children with stroke and how much worse the disabilities were among children who did not receive mechanical clot removal, compared to those who did,” he said lead investigator Kartik Bhatia, MBBS, Ph. D., MS, pediatric interventional neuroradiologist at the Sydney Children's Hospital Network in Westmead, Australia. “Now that we know how poor the recovery is for these children who have not received endovascular therapy, it is much easier to justify treatment options such as clot removal for children with a large blood vessel stroke.”
The study also found that about 80% of children with large vessel strokes met Australian and US requirements, as well as age, for adult eligibility for mechanical clot removal.
“Our healthcare systems also need improvements so that children with severe strokes can more easily receive mechanical clot removal,” Bhatia said. “These children should be offered treatments to clear blockages, just as we offer adults.”
The study had several limitations that may have affected the findings, including that it is a retrospective study that relied on medical records to identify levels of disability and that there was no standard selection process for treating patients.
A stroke is a medical emergency that occurs when blood flow to the brain is blocked by a blood clot, which is the most common type, or a ruptured blood vessel. In both children and adults, the signs of str
oke and the appropriate response are similar and can be recognized quickly by remembering the acronym FAST, which stands for Face Drooping, Arm Weakness, Slurred Speech, Time to Call 911.
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