PRESS-NEWS.org - Press Release Distribution
PRESS RELEASES DISTRIBUTION

Warfarin increases risk of stroke among atrial fibrillation patients in first 30 days of use

2013-12-19
(Press-News.org) Contact information: Emma Mason
wordmason@mac.com
European Society of Cardiology
Warfarin increases risk of stroke among atrial fibrillation patients in first 30 days of use Patients with atrial fibrillation – an irregular and often abnormally fast heartbeat – have nearly double the risk of suffering a stroke in the first 30 days after starting to take the anti-clotting drug warfarin compared to non-users, according to a study of over 70,000 patients.

The study, published online today (Thursday) in the European Heart Journal [1], found that the risk was particularly high in the first week after patients started to take the drug. In contrast, once the first 30 days had elapsed, the risk of a stroke was halved in patients taking warfarin compared to non-users.

Atrial fibrillation increases the risk of patients suffering a stroke, and warfarin is frequently prescribed for these patients to reduce the likelihood of this happening. However, randomised controlled trials of other anti-clotting drugs have suggested that there might be an increased risk of a stroke at the point when patients move from the trial drugs to warfarin. In addition, it has already been established that there is a possibility that warfarin leads temporarily to a hypercoagulable state – one in which the blood becomes more sticky and more likely to develop dangerous blood clots in the veins or arteries. This is thought to be due to the different effects of warfarin on the production of certain blood clotting factors that are dependent on Vitamin K.

Dr Laurent Azoulay, Assistant Professor in the Department of Oncology at McGill University (Montreal, Canada) and Project Leader at the Centre for Clinical Epidemiology, Lady Davis Institute, Jewish General Hospital in Montreal, led the research. "There is no question that warfarin is highly effective in preventing strokes in patients with atrial fibrillation. Thus, our finding that the initiation of warfarin may be associated with an increased risk of stroke should not deter physicians and patients from using this drug, since this likely affects a small number of patients. Future studies should confirm our results, and identify the small subset of patients who may be at risk. However, the results of our study suggest that physicians should be vigilant when initiating warfarin, particularly in the first week of use," he said.

"An interesting finding was that patients with a history of stroke prior to their atrial fibrillation diagnosis were at higher increased risk of developing a stroke during the initiation of warfarin. This is consistent with the hypothesis that the risk may be highest in patients with hypercoagulable states, which provides insight on the possible biological mechanisms that may be at play in this association.

"To our knowledge, this is the first population-based study to investigate whether the initiation of warfarin is associated with an increased risk of ischaemic stroke – a stroke caused by a blockage in an artery leading to the brain."

The researchers analysed data from 70,766 patients aged 18 or over, who were diagnosed with atrial fibrillation between 1 January 1993 and 31 December 2008. The study was carried out using the UK Clinical Practice Research Datalink, the world's largest primary care database. The researchers followed the patients for up to 16 years until an ischaemic stroke, death, end of registration with their primary care practice or end of the study period, whichever came first.

During that time, a total of 5519 patients experienced a stroke (two percent per year). During the first 30 days after starting warfarin, there was a 71% (nearly double) increased risk of ischaemic stroke when compared with patients taking no anti-coagulant drugs. The highest risk was in the first week of use, peaking on the third day after starting warfarin when there was a 133% (2.3-fold) increased risk of stroke. After 30 days, the risk of stroke among the warfarin patients halved. If the patients had a history of previous ischaemic stroke, they had a 245% (2.5-fold) increased risk during the first 30 days.

The researchers believe that the reason for the difference in the effects of warfarin may be that while the drug blocks the activation of clotting factors II, VII, IX and X, it also deactivates two other proteins, C and S, which are anticoagulants. Rapid depletion of protein C, in particular, might lead to a temporary hypercoagulable state.

The senior author of the study, Professor Samy Suissa, James McGill Professor of Epidemiology, Biostatistics and Medicine at McGill University (Montreal, Canada), said: "While these findings need to be confirmed in other settings, it would be imperative to also investigate whether the newer popular anticoagulants also carry this early risk." In the meantime, he suggests that "a bridging strategy using heparin – an injectable anticoagulant – at the initiation of warfarin treatment could be considered as a way to reduce the increased risk observed in the first 30 days of use."

The researchers hope to repeat the study using databases from other countries and settings.

### [1] "Initiation of warfarin in patients with atrial fibrillation: early effects on ischaemic strokes", by Laurent Azoulay, Sophie Dell'Anielllo, Teresa A. Simon, Christel Renoux, and Samy Suissa. European Heart Journal. doi:10.1093/eurheartj/eht499


ELSE PRESS RELEASES FROM THIS DATE:

Moa or less: Extinct 'robust' birds of New Zealand might not have been so robust after all

2013-12-19
Moa or less: Extinct 'robust' birds of New Zealand might not have been so robust after all Giant moa bird (Dinornis robustus, literally meaning 'robust strange bird') may not have actually had robust bones, according to new research conducted by ...

Heart disease and stroke continue to threaten US health

2013-12-19
Heart disease and stroke continue to threaten US health American Heart Association Annual Statistical Update DALLAS, Dec. 18, 2013 — Heart disease and stroke remain two of the top killers of Americans and pose a significant threat to millions of others, ...

Scientists solve a decades-old mystery in the Earth's upper atmosphere

2013-12-19
Scientists solve a decades-old mystery in the Earth's upper atmosphere New research published in the journal Nature resolves decades of scientific controversy over the origin of the extremely energetic particles known as ultra-relativistic ...

Messages sent via molecules can aid communication underground, underwater or inside the body

2013-12-19
Messages sent via molecules can aid communication underground, underwater or inside the body Scientists have created a molecular communications system for the transmission of messages and data in challenging environments such as tunnels, pipelines, underwater ...

Lemur babies of older moms less likely to get hurt

2013-12-19
Lemur babies of older moms less likely to get hurt Finding emerges from Lemur Center's 35 years of detailed records DURHAM, N.C. -- A long-term study of aggression in lemurs finds that infants born to older mothers are less likely to get hurt than those born to younger mothers. The ...

York U molecular communication researchers send world's first text message using vodka

2013-12-19
York U molecular communication researchers send world's first text message using vodka TORONTO, Dec. 18, 2013 — After successfully text messaging 'O Canada' using evaporated vodka, two York University researchers and their UK-based counterpart say their simple system ...

Growers the big winners in Malawi's tobacco industry

2013-12-19
Growers the big winners in Malawi's tobacco industry Study looks at social, economic and environmental impacts and trade-offs of an expanding tobacco industry Tobacco growers are the big winners, while the environment and people who have lost ...

Researchers identify genetic marker of resistance to key malaria drug

2013-12-19
Researchers identify genetic marker of resistance to key malaria drug Detection of drug resistance would aid public health efforts WHAT: An international team of researchers has discovered a way to identify, at a molecular ...

Mountain pikas, relatives of rabbits, survive at warm sea-level temperatures by eating mosses

2013-12-19
Mountain pikas, relatives of rabbits, survive at warm sea-level temperatures by eating mosses Mosses also may protect high-peak pikas against climate change effects In some mountain ranges, Earth's warming climate drives rabbit relatives known as pikas to higher elevations--or ...

NASA sees Tropical Cyclone Bruce develop near Cocos Island

2013-12-19
NASA sees Tropical Cyclone Bruce develop near Cocos Island NASA's Aqua satellite flew overhead as the fourth tropical cyclone of the Southern Indian Ocean cyclone season developed today, December 18, while it was passing to the northwest of Cocos Island, Australia. The ...

LAST 30 PRESS RELEASES:

Signs identified that precede sudden arrhythmic death syndrome in young people

Discovery of bacteria's defence against viruses becomes a piece of the puzzle against resistance

Pre-eclampsia is associated with earlier onset and higher incidence of cardiovascular risk factors

Warwick astronomers discover doomed pair of spiralling stars on our cosmic doorstep

Soil conditions significantly increase rainfall in world’s megastorm hotspots

NK cells complexed with bispecific antibody yield high response rates in patients with lymphoma

Planetary health diet and mediterranean diet associated with similar survival and sustainability benefits

Singapore launches national standard to validate antimicrobial disinfectant products

Molecular stool test could improve detection of tuberculosis in adults with HIV

Suspected fibrocartilaginous embolus in Asian small-clawed otter (Aonyx cinereus)

Enhancing heat transfer using the turbulent flow of viscoelastic fluids

Exercise as an anti-ageing intervention to avoid detrimental impact of mental fatigue

UMass Amherst Nursing Professor Emerita honored as ‘Living Legend’

New guidelines aim to improve cystic fibrosis screening

Picky eaters by day, buffet by night: Butterfly, moth diets sync to plant aromas

Pennington Biomedical’s Dr. Leanne Redman honored with the E. V. McCollum Award from the American Society for Nutrition

CCNY physicists uncover electronic interactions mediated via spin waves

Researchers’ 3D-printing formula may transform future of foam

Nurture more important than nature for robotic hand

Drug-delivering aptamers target leukemia stem cells for one-two knockout punch

New study finds that over 95% of sponsored influencer posts on Twitter were not disclosed

New sea grant report helps great lakes fish farmers navigate aquaculture regulations

Strain “trick” improves perovskite solar cells’ efficiency

How GPS helps older drivers stay on the roads

Estrogen and progesterone stimulate the body to make opioids

Dancing with the cells – how acoustically levitating a diamond led to a breakthrough in biotech automation

Machine learning helps construct an evolutionary timeline of bacteria

Cellular regulator of mRNA vaccine revealed... offering new therapeutic options

Animal behavioral diversity at risk in the face of declining biodiversity

Finding their way: GPS ignites independence in older adult drivers

[Press-News.org] Warfarin increases risk of stroke among atrial fibrillation patients in first 30 days of use