A study into the structure of blood vascular network structure found that it is dynamic and can adapt to external factors, resulting in a kind of memory of certain events such as an ischaemic stroke. In particular, the study researchers found that rarely used connections incrementally weaken until they disappear eventually.
Researchers from the Max Planck Institute for Dynamics and Self-Organization in Göttingen and the Technical University of Munich used computer simulations to model vascular networks and identified adaptation rules for their connections.
“We found that the strength of a connection within a network depends on the local flow,” explained Karen Alim, corresponding author of the study. “This means that links with a low flow below a certain threshold will decay more and more until they eventually vanish,” she continued. Since the limited amount of material available to build the vascular system needs to be efficiently used, this mechanism offers an elegant way to streamline the vascular system.
Persistent changes in the network
Once a connection has become very weak due to a low flow rate, recovering that connection is very difficult. For example, a blood vessel blockage of the type that could lead to an ischaemic stroke. During an ischaemic stroke, some blood vessels in the affected region are weakened by the blockage.
“We found that in such a case, adaptations in the network are permanent and are maintained after the obstacle is removed. One can say that the network prefers to reroute the flow through existing stronger connections instead of re-growing weaker connections – even if the flow would require the opposite,” explained Komal Bhattacharyya, principal author of the study.
The researchers have thus shown that blood flow permanently changes even after successful removal of the clot. This memory capability of networks can also be found in other living systems: for example, the slime mould Physarum polycephalum uses its adaptive network to navigate its environment based on imprints by food stimuli, as demonstrated previously.
Researchers at the University of East Anglia are launching a new study to investigate how sleep can aid in stroke recovery, by examining whether people’s sleep patterns influence recovery of neuromuscular function.
Lead researcher Prof Valerie Pomeroy, from UEA’s School of Health Sciences, said: “We want to better understand how the brain recovers after a stroke – so we will be investigating how stroke survivors regain movement, and how this is influenced by sleep and time.
“We hope to find out more about sleep patterns that are beneficial for movement recovery after stroke.”
The team are looking for people in the region who have had a stroke to take part in the study. Participants will undertake measures of daily activity, sleep and movement.
The project will involve measuring people’s movement using small sensors placed on the skin’s surface that record natural muscle activity whilst they carry out a daily task – picking up a telephone.
Participants will be asked to attend two visits at the university, during which participants will undertake the movement measures and complete questionnaires about how they sleep.
In-between visits, participants will wear a motion watch on each wrist for seven days to measure their everyday activity at home.
Prof Valerie Pomeroy said: “There is strong evidence that physiotherapy improves the ability of people to move and be independent after a stroke. But at six months after stroke many people remain unable to produce the movement needed for everyday activity such as answering a telephone.
“We are undertaking this study to understand more about whether this situation could be improved by using interventions to change a patient’s sleep pattern and thus improve recovery of movement ability.”
A new guideline published in the journal Stroke reveal that home treatments or preventive therapies used to manage intracerebral haemorrhages (ICH) are not as effective as previously believed.
The guideline from the American Heart Association/American Stroke Association includes recommendations on surgical techniques, individual activity levels after an ICH, and additional education and training for at-home caregivers. It reflects advances in the intracerebral haemorrhage field since the last guideline on ICH management was published in May 2015.
“Advances have been made in an array of fields related to ICH, including the organisation of regional health care systems, reversal of the negative effects of blood thinners, minimally invasive surgical procedures and the underlying disease in small blood vessels,” said Steven M. Greenberg, M.D., Ph.D., FAHA, chair of the guideline writing group.
Updates to Standard Care Practices
The new guideline suggests that many techniques widely considered “standard care” are unnecessary. For example, wearing compression socks or stockings to prevent deep vein thrombosis after ICH was not found to be effective. Instead, use of intermittent pneumatic compression may be helpful if started on the same day of an ICH diagnosis.
“This is an area where we still have a lot of exploration to do. It is unclear whether even specialised compression devices reduce the risks of deep vein thrombosis or improve the overall health of people with a brain bleed. Even more research is needed on how new blood clot prevention medications may help, especially within the first 24 to 48 hours of the first symptoms,” said Dr Greenberg.
Use of anti-seizure medicines or anti-depressants after ICH is also updated; neither of these classes of medications helps a person’s overall health unless a seizure or depression is already present, therefore, they are not advised for most people. Anti-seizure medication did not contribute to improvements in functionality or long-term seizure control, and the use of anti-depressants increased the chance of bone fractures.
The guideline writing group also addresses previously standard in-hospital therapies. They suggest administering steroids to prevent complications from a bleeding stroke is ineffective and highlight that platelet transfusions, unless used during an emergency surgery, may worsen the stroke survivor’s condition.
Surgical Intervention
Some research suggests procedures with a less invasive approach are less likely to damage brain tissue while removing the fluid build-up.
“The evidence is now reasonably strong that minimally invasive surgery may improve the likelihood that a patient will survive following a moderate or large ICH,” says Greenberg. “It is less clear, however, whether this or any other kind of surgical procedure improves the chances of survival and recovery from ICH, which are our ultimate goals.”
Recovery and Rehabilitation
Stroke rehabilitation includes several strategies to help restore the individual’s quality of life, and the guideline reinforces the importance of having a multi-disciplinary team to develop a plan for recovery. Research suggests a person with a mild or moderate ICH may begin activities like stretching, dressing, bathing and other normal daily tasks 24–48 hours after the stroke to improve survival rate and recovery time; however, moving too much or too intensely within 24 hours is linked to an increased risk of death within 14 days after an ICH.
Home Caregivers
The guideline also recommends education, practical support and training for family members so they may be involved and knowledgeable about what to expect during rehabilitation.
Other Highlights
The guideline suggests there may be an opportunity to prevent ICH in some people by using MRI which can image small blood vessel damage. In addition, major risk factors for small vessel damage are high blood pressure, Type 2 diabetes and older age. Blood thinners remain an important topic since the use of these medications may increase complications and death from a bleeding stroke. Updated guidance is provided for immediate reversal of the newer blood thinners like apixaban, rivaroxaban, edoxaban and dabigatran, as well as older medications like warfarin or heparin.
Renewed emphasis is placed on the complexities of a do-not-attempt-resuscitation (DNAR) status versus the decision to limit other medical and surgical interventions. The writing group highlights the need to educate medical professionals, stroke survivors and/or the individual’s caregiver about the differences. The guideline recommends the severity of a hemorrhage, as measured by the standard scales, not be used as the sole basis for determining life-saving treatments.
More intensive hypertension treatment could help prevent or delay strokes in older adults, according to an analysis of results from randomised clinical trials published in the Journal of the American Geriatrics Society.
The researchers initially screened 22 trials for inclusion. Nine trials involving 38 779 adults with an average age ranging from 66 to 84 years were included in the analysis, with follow-up times ranging from 2.0 to 5.8 years.
On average, the researchers found that it took 1.7 years to prevent 1 stroke for 200 older persons treated with more intensive hypertension treatment.
For older adults with baseline systolic blood pressures below 150 mmHg, the time to benefit from more intensive hypertension treatment was longer than 1.7 years; for older adults with baseline systolic blood pressure above 190 mmHg, the time to benefit was shorter than 1.7 years.
In their discussion, the researchers noted the risks of aggressive hypertension treatment, including hypotension, syncope and falls. However, they noted that emerging evidence shows that the increase in fall risk is transient.
“While the 2017 American College of Cardiology/American Heart Association guidelines recommend individual risk discussions about hypertension treatment for primary prevention in older adults, there is a critical gap in data about how long a patient needs to receive blood pressure treatment before they will benefit – or the blood pressure treatment’s time to benefit,” said lead author Vanessa S. Ho, MS, of California Northstate University College of Medicine. “A treatment’s time to benefit is an especially important consideration for patients with a limited life expectancy who may experience immediate burdens or harms from any additional medication.”
Despite the fact that hospitalised patients are in a monitored environment, stroke evaluation and treatment are often delayed compared to patients arriving with a stroke at the emergency department, contributing to higher rates of morbidity and mortality for in-hospital stroke.
This is according to an American Heart Association scientific statement published in Stroke. This scientific statement was discussed at the Association’s International Stroke Conference in New Orleans. An American Heart Association scientific statement is an expert analysis of current research and may inform future clinical practice guidelines. This follows on from a previous 2019 update on recommendations systems of care to improve patient outcomes in stroke.
The statement outlines five elements for the development of hospital systems of care and targeted quality improvement to reduce delays and optimise treatment to improve outcomes for patients who experience an in-hospital stroke. In-hospital stroke is a stroke that occurs during a hospitalisation for another diagnosis and affects between 35 000 and 75 000 hospitalised patients annually in the United States.
The five core elements of the statement are:
training all hospital staff on stroke signs, symptoms and activation protocols for in-hospital stroke alerts;
creating rapid response teams with dedicated stroke training and immediate access to neurologic expertise;
standardising the evaluation of potential in-hospital stroke patients with physical assessment and imaging;
eliminating and addressing potential treatment barriers including interfacility transfer to advanced stroke treatment; and
establishing an in-hospital stroke quality oversight program delivering data-driven performance feedback and driving targeted quality improvement efforts.
The statement encourages institutions to develop a plan for in-patient stroke response teams that includes education, quality review and specified oversight.
The statement was developed by the writing committee on behalf of the American Heart Association’s Stroke Council; the Council on Arteriosclerosis, Thrombosis and Vascular Biology; the Council on Cardiovascular and Stroke Nursing; the Council on Clinical Cardiology; and the Council on Lifestyle and Cardiometabolic Health. The diverse committee included experts in nursing, neurology, internal medicine, neurocritical care, neurosurgery and neurointerventional radiology. The American Academy of Neurology affirms the value of this statement as an educational tool for neurologists, and the American Association of Neurological Surgeons/Congress of Neurological Surgeons Cerebrovascular Section affirms the educational benefit of this statement.
American Heart Association scientific statements promote greater awareness about cardiovascular diseases and stroke issues and help facilitate informed health care decisions. Scientific statements outline what is currently known about a topic, and what areas need additional research. While scientific statements inform the development of guidelines, they do not make treatment recommendations. American Heart Association guidelines provide the Association’s official clinical practice recommendations.
The trace metal selenium could help reverse the cognitive impact of stroke and boost learning and memory in ageing brains, according to a study published in Cell Metabolism.
Previous studies on the impact of exercise on the ageing brain found levels of a protein key to transporting selenium in the blood were elevated by physical activity.
Lead researcher Dr Tara Walker said: “We’ve known for the last 20 years that exercise can create new neurons in the brain, but we didn’t really understand how,” Dr Walker said.
The research team sought to find out whether dietary selenium supplements could replicate the effects of exercise.
“Our models showed that selenium supplementation could increase neuron generation and improve cognition in elderly mice,” Dr Walker said. “The levels of new neuron generation decrease rapidly in aged mice, as they do in humans. When selenium supplements were given to the mice, the production of neurons increased, reversing the cognitive deficits observed in ageing.”
Selenium is an essential trace metal which can play an important role in human health. It is absorbed from soil and water and is found in foods such as grains, meat and nuts, with the highest levels found in Brazil nuts. The researchers also investigated whether selenium would have an impact on post-stroke cognitive decline.
“Young mice are really good at the learning and memory tasks, but after a stroke, they could no longer perform these tasks,” Dr Walker said. “We found that learning and memory deficits of stroke affected mice returned to normal when they were given selenium supplements.”
Dr Walker said the results opened a new therapeutic avenue to boost cognitive function in people who were unable to exercise due to poor health or old age.
“However, selenium supplements shouldn’t be seen as a complete substitute for exercise, and too much can be bad for you,” she said. “A person who is getting a balanced diet of fruits, nuts, veggies and meat usually has good selenium levels. But in older people, particularly those with neurological conditions, selenium supplements could be beneficial.”
A new study published in Neurology shows that women are underrepresented in stroke clinical trials compared to the proportion who have strokes in the general population.
“Making sure there are enough women in clinical studies to accurately reflect the proportion of women who have strokes may have implications for future treatment recommendations for women affected by this serious condition,” said study author Cheryl Carcel, MD, of The George Institute for Global Health in Sydney, Australia. “When one sex is underrepresented in clinical trials, it limits the way you can apply the results to the general public and can possibly limit access to new therapies.”
The study analysed 281 stroke trials conducted between 1990 and 2020, with a total of 588 887 participants. Of these, only 37.4 % were women. The average prevalence of stroke in women across the countries included was 48%.
Results were calculated in participation-to-prevalence ratio, a relative measure that weights the percentage of women in a trial compared to their proportion in the total population with that disease. A ratio of one indicates that the percentage of women in the study is the same as the percentage of women with the disease in the general population. An acceptable range for an ideal ratio of female participation is between 0.8 and 1.2.
Overall, women were found to be underrepresented relative to their prevalence in the underlying population, with a consistent ratio of 0.84 over time. They found the greatest differences in trials of intracerebral haemorrhage, with a ratio of 0.73; trials with average participant age under 70, with a ratio of 0.81; non-acute interventions, with a ratio of 0.80; and rehabilitation trials, with a ratio 0.77.
“Our findings have implications for how women with stroke may be treated in the future, as women typically have worse functional outcomes after stroke and require more supportive care,” Dr Carcel said. “We will only achieve more equitable representation of women in clinical trials when researchers look at the barriers that are keeping women from enrolling in studies and actively recruit more women. People who fund the research also need to demand more reliable, sex-balanced evidence.”
While there are well-known common lifestyle and health factors that contribute to stroke risk, including smoking, high blood pressure, high cholesterol, and lack of physical activity, there is another overlooked factor that could also affect stroke risk – altitude.
Higher altitude means less oxygen availability, to which people living there have adapted. However, how this environment affects someone’s risk for stroke is still unclear. Anecdotal evidence suggests that short-term exposure to low oxygen can contribute to increased blood clotting and stroke risk, but the risk among people who permanently live at high altitude is not clear.
Researchers in Ecuador are in a unique position to explore these phenomena, as the presence of the Ecuadorian Andes means that people in the country live at a wide array of altitudes. Study lead author Esteban Ortiz-Prado, and Professor, Universidad de las Americas, explained:
“The main motivation of our work was to raise awareness of a problem that is very little explored. That is, more than 160 million people live above 2500 metres and there is very little information regarding epidemiological differences in terms of stroke at altitude. We wanted to contribute to new knowledge in this population that is often considered to be the same as the population living at sea level, and from a physiological point of view we are very different.”
The researchers drew on hospital records in Ecuador from between 2001 and 2017, and analysed rates of stroke hospitalisation and mortality among people who live at four different elevation ranges: low altitude (under 1500m), moderate altitude (1500–2500m), high altitude (2500–3500m) and very high altitude (3500–5500m).
Analysis showed that people who lived at higher altitudes (above 2500m) tended to experience stroke at a later age compared with those at lower altitudes. Intriguingly, people who lived at higher altitudes had a lower stroke hospitalisation or mortality risk. This protective effect was greater between 2000 and 3500m, tapering off somewhat above 3500m. In South Africa, Johannesburg sits above 1700m altitude.
One explanation for this finding may be that people who live at high altitude have adapted to the low oxygen conditions, and more readily grow new blood vessels to help overcome stroke-related damage. They may also have a more developed vascular network in their brains that helps them to make the most of the oxygen they take in, but this could also protect them from the worst effects of stroke.
A new study emphasises the importance of survivors of first-time stroke or transient ischaemic attack (TIA) to take medications on an ongoing basis, highlighting long-term associations with survival.
Stroke is the second leading risk of death worldwide, with In 2016, the average lifetime risk of stroke after 25 for the global population was 24.9%. Nearly half of all survivors of stroke are expected to experience a recurrent cardiovascular event within 10 years. Specific medications help to prevent this long-term risk, but adherence to these agents is often suboptimal among patients.
The study, published in Stroke, demonstrates the importance of medication adherence after stroke to maximise survival, even for patients with near-perfect adherence. These findings are in support of targeted initiatives to maximise medication adherence after stroke/TIA, such as implementation of medication reminder systems, mobile health technologies, increased follow-up by clinicians or complex behaviour change programs.
Drawing from Australian databases, the study enrolled 8363 adult patients who survived a first stroke or TIA between July 2010 and June 2014, with follow-up for a further three years. For patients with one-year adherence above 60%, each 10% improvement in adherence was associated with a 13-15% reduction in mortality risk. These results suggest that aiming for an arbitrary adherence target of 80% may be inappropriate as maximal survival benefits were observed closer to 100% adherence.
The study’s lead author, Associate Professor Monique Kilkenny, said continued use of secondary prevention medications can be improved with several factors: provision of medication on hospital discharge, regular contact with a primary care physician, and specialist physician contact.
“These findings represent important implications for practice by highlighting the value of efforts to improve medication adherence post-stroke/TIA, even among patients with near-perfect adherence,” said Associate Professor Kilkenny.
“Our findings provide evidence in support of targeted initiatives to maximise medication adherence after stroke/TIA and there is considerable scope for further interventions to improve medication adherence.”
Screening for atrial fibrillation in 75- and 76-year-olds using thumb ECGS could reduce the risk of stroke, severe bleeding and death, according to a large-scale Swedish study.
Atrial fibrillation (AF) is associated with a five-fold increased risk of stroke, and the symptoms are often deleterious since large blood clots can form in the heart, breaking free and posing a stroke risk. Still, countries do not screen the general population for atrial fibrillation, but rather treat those patients who are discovered during routine care. This study by the Karolinska Institutet in Sweden and published in The Lancet, investigated the effectiveness of screening for AF.
“There has never really been a study that examines if it would be beneficial to screen for atrial fibrillation, which is why we wanted to investigate it,” said Emma Svennberg, cardiologist at the Karolinska University Hospital, Huddinge, and researcher at the Department of Medicine, Huddinge, Karolinska Institutet.
The study included almost 28 000 participants aged 75 or 76, randomised to be invited either to screening or to a control group, who received standard care. Of those invited to screening, more than half choose to participate. They completed a health questionnaire and performed a so-called thumb ECG (electrocardiogram), which involves placing one’s thumbs on an ECG device that measures the heart’s electrical activity.
Those without atrial fibrillation were asked to record their heart rhythm twice daily for two weeks using the ECG device which they took home. If the device registered irregular heart rhythms, the participants were referred to a cardiologist for a standardised work-up and, if there were no contra-indications, initiation of oral anticoagulant therapy.
The study’s 28 000 participants were then followed for at least five years. More detections of atrial fibrillation were recorded in the screening group, which also had a slightly lower incidence of death, stroke and severe bleeding than the control group.
“In total, 31.9 percent of those in the screening group experienced a negative event compared to 33 percent in the control group,” said Johan Engdahl, adjunct lecturer at the Department of Clinical Sciences, Danderyds Hospital, at Karolinska Institutet. “Now, that may sound like a small difference, but you must bear in mind that only about half of those invited to screening participated and it’s possible we would have seen a more pronounced difference had more people turned up for screening. Those who participated in the screening had significantly fewer negative events.”
Based on the findings, the researchers estimated that at least 2300 cases of stroke or death could be avoided per year in Sweden if a national screening of atrial fibrillation in the elderly was introduced.
