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warfarin

Self-monitoring of blood thinners halves your risk of clots

Carl Heneghan
Last edited 1st December 2011

Here are some links to news stories of cebmblog and colleagues work published in the Lancet today

Self-monitoring of oral anticoagulation: systematic review and meta-analysis of individual patient data Lancet

Self-Monitoring of Blood Thinner May Halve Clot Risk
MSN Health
People taking the blood-thinning drug warfarin who monitor their own blood and adjust their dosage can reduce the risk of blood clots by half, British researchers report. Warfarin is taken to prevent potentially deadly clots in patients with conditions such as atrial fibrillation – an abnormal heart rhythm – or a mechanical heart valve. But if the blood is thinned too much, serious bleeding can occur. Keeping the drug in check requires monthly monitoring and frequent doctors visits. ‘The concept of self-care and self-monitoring is a growing part of health care. It is used widely in diabetes, asthma and hypertension management,’ said lead researcher

Dr Carl Heneghan, director of the Centre for Evidence-Based Medicine at the University of Oxford. ‘The evidence shows that self-monitoring is an effective strategy to reduce thromboembolic events in patients taking oral anticoagulants such as warfarin,’ he added.

Home monitoring of ‘blood thinners’ is effective
Web MD

Patients Can Safely Manage Blood Thinners Themselves
MedPage Today

There is also a neat peice by Jonathan Wood from the University of Oxford press office Blood clot risk halved for patients checking own warfarin dose

Patients who monitor their own treatment with warfarin or other blood-thinning drugs reduce their risk of developing blood clots by half, an Oxford University study has found.......

A Risky Business

Kamal Mahtani
Last edited 17th August 2011

A great deal of General Practice is essentially about managing risk. Every time a patient walks through your consulting door you are basically thinking “what are the chances of this patient coming to harm from what they are about to tell me?” Some patients will fall into a category of “high risk” needing immediate or quick treatment. Others may have a degree of risk that necessitates either further investigations or monitoring. Or there may be low risk cases which can be assessed, reassured or treated. This is all supposed to happen within 10 minutes.

But how far should we go to convey that risk to our patients and what is the best way to do it? A recent scenario at my practice made me pause for thought. The cardiologists had advised us to have a discussion with a patient on the merits and risks of aspirin versus warfarin for their atrial fibrillation.

How could that conversation go?

“Right Mr X, the cardiologists have written to me and asked me to help you decide between warfarin or aspirin. They mention in the letter that the risk of you now having a stroke is about 6% per year, however aspirin reduces that risk by about 25% but with warfarin there is about a 45% risk reduction. However, the number needed to treat with warfarin is 37, but bear in mind that warfarin increases the annual absolute risk of major haemorrhage by 2%, so it’s up to you, which one would you prefer? ”

“umm…I’m sorry Doctor, I didn’t understand all of that”

“No neither did I”

So how should we explain risk to patients? The 2002 BMJ clinical review “Explaining risks: turning numerical data into meaningful pictures” by Edwards and colleagues is certainly worth a read. More recently, a study in the Annals of Family Medicine also tried to answer the question. The group surveyed 934 consecutive patients drawn from family practitioners’ waiting rooms in Auckland, New Zealand. Patients were asked to rate how much various modes of communicating the benefits of therapy, to their 5-year CVD risk score, would encourage them to take medication daily. The modes offered to them included: relative risk, absolute risk, odds, number needed to treat, and natural frequencies. The same information was presented in 2 pictorial forms (bar graphs and 10 × 10 people charts). Most patients (61.8%) preferred a doctor to give an opinion than to explain using either numbers or pictures. More than half also preferred a pictorial presentation to numbers; and of the numerical presentations patients found relative risk reduction most encouraging, with absolute risk reduction rated second overall and numbers needed to treat (NNT) the least likely to be persuasive to take their medication.

So should this mean to our practice? Remember EBM is the integration of the best clinical practice, personal expertise and individual patient preference. The latter component is dependent upon the patient fully understanding the risks and benefits of treatment so that a shared management plan can be reached. Having an idea of what those risks mean ourselves is the first step but finding the best way to convey it to our individual patients in as simplest way as possible is perhaps the bigger challenge.

Atrial fibrillation-potential of new treatments

Ami Banerjee
Last edited 21st April 2011

Everybody seems to be interested in atrial fibrillation (AF) at the European Stroke Conference this week in Barcelona. So they should be as AF is the most common heart rhythm problem, affecting up to 1% of the population, and increasing with age. Usually an electrical impulse passes from the upper chambers of the heart (the atria) to the lower chambers (the ventricles), which pump blood around the body. If the electric impulse is not conducted properly, the atria “fibrillate” or “flutter” instead of beating in the usual coordinated way. When this happens, clots tend to form in the heart. AF increases risk of stroke by 5-fold due to these clots being thrown off into the brain. Strokes due to AF tend to be more severe and disabling than other types of strokes, with 25% mortality rate. But we have known about AF and the need to prevent strokes by thinning the blood with warfarin for many years, so why all the sudden interest?

We know that warfarin is better than aspirin and clopidogrel and aspirin alone in preventing strokes in people with AF from existing trial data. Therefore, warfarin is recommended in people with moderate or high risk of stroke. The problem is that people on warfarin need their blood monitoring and there is a risk of bleeding, as well as lots of interactions with other drugs and food. In people who cannot take warfarin, aspirin is better than nothing. I have previously mentioned the evidence that self-monitoring of INR levels in patients taking warfarin leads to better results. However, there has been a search for new drugs which avoid blood monitoring and are easier to take.

Dabigatran is such a drug. The RE-LY trial compared dabigatran to warfarin in stroke prevention in patients with AF other risk factors for stroke,such as age or heart failure. The relative risk of stroke with digabatran was two-thirds that of warfarin (remind yourself of what relative risk is). Importantly the new drug caused much less bleeding and you don’t have to worry which other drugs you are taking or what you are eating. There are lots of other drugs being trialled at the same time, but dabigatran is probably the most promising and has got the best results in the trials.

Another way to treat the problem is to treat the AF directly and try and make the heart rhythm return to normal. This has traditionally been done with drugs (known as anti-arrhythmics such as amiodarone), but surgical therapies have become available over the last 20 years. Over the last 10-15 years, cardiologists have been increasingly using techniques to burn the electrical pathways that are at fault in the atria. The procedure is currently recommended in patients who do not respond to drugs and still have symptoms from their AF such as palpitations. There are trials ongoing to test this long procedure, but one of the presenters (a cardiologist who was a proponent of the technique from France) raised the issue that it is difficult to envisage a time when the procedure will be available to large enough section of the population with AF. In other words, it requires so much time and expertise that providing enough training resources, human resources and enough hospital resources may be challenging. But would we want to offer everybody this procedure anyway? There must be cheaper, more effective alternatives.

Stroke and AF are totally intertwined and both are growing problems in ageing populations across the world. That is why researchers and drug companies are so interested because the potential rewards are huge.

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