Dr Tim Holt

Brief Outline:

Tim Holt is a Senior Clinical Research Fellow in the Nuffield Department of Primary Care Health Sciences at the University of Oxford and a General Practitioner in Oxfordshire. With a strong research and professional interest in atrial fibrillation, he brings considerable expertise to this website.

Dr Tim Holt explains how people with AF have an irregular heartbeat. They may experience symptoms such as palpitations or have no symptoms at all.

Atrial fibrillation, is a common condition, particularly in older people and in people with certain other conditions, in which the heart beats irregularly. As well as beating irregularly, it also tends to beat quite fast until the condition is diagnosed and the symptoms are controlled. So it often presents to people with symptoms of palpitations or possibly of dizziness and breathlessness and sometimes a discomfort in the chest but other people get no symptoms at all and sometimes their AF is detected when they’re examined by a doctor or a nurse in the practice or in other situations.

The normal heart rate is, you know, somewhere between perhaps sixty and eighty and in people with atrial fibrillation, it’s often higher than that. Sometimes it can be very high. It can go over a hundred and forty, in which case, it’s quite a serious emergency. Other times it’s much nearer to normal but it’s irregular. That’s the real defining characteristic. It’s not beating in a regular pattern. It’s beating irregularly and, as I say, sometimes that produces symptoms and other times it’s not detected by the patient until they’re examined by somebody.

Dr Tim Holt explains how an ECG can detect an irregular heartbeat.

An ECG is a device which detects electrical impulses from the heart, so the person has electrical leads attached to them on the chest, over to the left side of the chest and on their arms and leg and this detects the pattern of impulses coming from the heart, so it produces a trace and, where each heartbeat is recorded as a disruption to the baseline and this gives a very useful way of detecting the irregularity in the heart rate.

Dr Tim Holt explains why AF does not always show up on an ECG.

It doesn’t always show up in the sense that the atrial fibrillation can sometimes be coming and going. So a person who’s got atrial fibrillation but it’s coming and going and is not there all the time might have an ECG done at the time when it’s not there and that’s a real problem because the person still has a problem, even if they have no symptoms and they have only intermittent AF, they are still at high risk of having a stroke. So this is why it’s very important, if atrial fibrillation is suspected, not to rely simply on one ECG because it might have missed it.

So what would you do with people like that?

Well, if the suspicion of atrial fibrillation is significant, then such a person should be referred to a specialist to have what’s called a Holter monitor put on. Sometimes these are available in GP practices as well. The device is attached to the patient and they wear it usually for forty eight hours, some devices last longer than that, and it gives a much more, a much longer tracing which is much more likely to pick it up if the problem is just coming and going on and off.

Dr Tim Holt explains why some people might be more likely to get AF.

Atrial fibrillation is particularly associated with getting older so that, you know, age is a particularly strong risk factor for atrial fibrillation. People are more likely also to get it if they have anything else affecting their heart, particularly coronary heart disease, and also people with hypertension, in the long run, are more likely to develop atrial fibrillation. People who have damaged the heart for other reasons including alcohol, too much alcohol in their lives are more likely and then there are other causes including thyroid conditions which can raise the risk. So there are a number of medical conditions, which can add to any sort of genetic predisposition to increase an individual’s risk.

Dr Tim Holt explains what a diagnosis of AF might mean long-term.

Well, it means regular reviews. It means taking medication regularly. If the person is taking warfarin, then they need regular blood tests and they’ll need to be careful about certain aspects of their lives. So all of these things affect their lives and they may or may not have remaining symptoms, even when their heart rate is controlled. So it’s certainly a very significant condition to have but, in many cases, it can be successfully treated and the risk of stroke minimised by taking anticoagulant treatment.

So what are the long term prospects for people with atrial fibrillation?

 I think it depends on how well they respond to treatment. I’ve had lots of patients who’ve had their symptoms controlled relatively easily and they’ve led normal lives. They may well get symptoms that I’m not aware of that may have more of an impact that I’m aware of as a GP but, nevertheless, they manage to continue doing all the things that they want to do in life. And then there are other people, who are older, who are perhaps more affected by it and it’s a condition that’s commoner as you get older and, obviously, in older people it’s more tricky to get the treatment regime which suits them, which doesn’t cause side-effects, which doesn’t interfere with any other medication that they’re taking and they’re probably more affected by it.

Dr Tim Holt talks about current research into atrial fibrillation.

Well, I think there’s quite a lot of research at the specialists and the specialist side over the best techniques to control heart rate and restore heart rhythm, restore the normal rhythm using these procedures of ablation and, you know, pacemakers and cardioversion. There’s also research going on to find out whether these procedures actually have a long term impact on stroke risk because, if that were the case, then obviously there’d be a case for providing them in a much more widespread way to more patients and that’s a really important research question to answer.

And then from the other sort of the service organisation side, I think there’s quite a lot of research needed to ensure that patients actually access the treatments that we know are beneficial including the anticoagulants, which have a very substantial impact on the person’s risk of having stroke in the long run.

Dr Tim Holt explains the types of anti-arrhythmic medication used to treat AF.

There are a number of drug treatments that can be used to either reduce the heart rate and control the heart rate. They’re called rate control measures and then there are other drugs, which are given usually by specialists, that can also actually restore or help to maintain the normal rhythm once it’s been restored. So, in general practice, we often use rate control medications like beta blockers or calcium channel antagonists or digoxin to control the patient’s heart rate and that often relieves a lot of their symptoms. And, when their symptoms are relieved, the next question is whether this person needs to be started on blood thinning treatment to reduce their stroke risk.

There are drugs used which are largely in the remit of specialists and I’m thinking of drugs like amiodarone and dronedarone and also drugs like flecainide, which are prescribed and initiated in a specialist setting. They have side effects that all need to be discussed with the patient. It needs to be clear what the purpose of the drug is, whether it is to stabilise the heart or simply to control the rate. Some of these drugs are only used in the situation where the more commonly used drugs have not succeeded in controlling the heart rate. In other situations they’re used to stabilise the heart and make the cardioversion treatments, where the heart rhythm is restored electrically, to make that process more successful.

Dr Tim Holt discusses the side effects people may experience on anti-arrhythmic medication.

Yes, there are some side effects. Beta blockers, for instance, are quite commonly associated with the feeling of tiredness and lethargy and an inability to exercise as well as the person could previously. And that’s quite a common quite a common problem, quite a problem for some people. Similarly, calcium channel antagonists can often cause swollen ankles, which is a problem. Either of those two drugs can reduce the blood pressure and that can sometimes be reduced further than is intended so that can cause dizziness. Either of those two can also reduce the heart rate, which, of course, is the purpose of giving them but there’s always some risk of it going down too low. And then for digoxin there are a number of other side effects, which are quite likely to occur if the dose is too high for the patient. So it’s very important to be, if you’re using the drug digoxin, to make sure that the patient isn’t getting too much of it and, as the person gets older and their kidney function perhaps reduces over time, then the dose of the digoxin needs to be reviewed to decide whether it’s still appropriate.

So what sort of side effects might people expect on digoxin?

Well, quite a common side effect is nausea and loss of appetite and weight loss and sometimes this occurs in people who have been taking digoxin for some time and those sorts of symptoms, obviously, can be caused by lots of different conditions but if other conditions have been ruled out, you always need to remember that those symptoms can be related to that drug. And it then may be necessary to either reduce the dose and see whether the person feels better or to actually check their blood levels.

Dr Tim Holt explains what cardioversion is and when it is used.

So cardioversion is a means of restoring the normal regular rhythm of the heart and it can either be done using drug therapy or it can be done by producing an electrical treatment to the heart, which is done with the patient sedated so they’re not aware of it, where the heart is treated electrically to restore the regular rhythm. And sometimes drug therapy is given to make that electrical procedure more likely to succeed. So it can be quite successful. Some people respond to it, other people don’t. Some people need several goes before it’s successful and there is always some reason, some risk of it recurring later.

In what sort of circumstances would cardioversion be used?

Well, it’s used for people who’ve got persistent atrial fibrillation. It can’t be used in somebody who’s got intermittent atrial fibrillation that’s coming and going. You know, it’s, there’s no point in giving it to somebody who is currently in the normal rhythm. So it’s usually given to people who’ve got persistent atrial fibrillation. 

Dr Tim Holt explains why cardioversion is not always successful.

It’s much more likely to succeed if the atrial fibrillation has started recently. In people who have possibly had the condition for years, when they’re diagnosed, it’s less likely to succeed but, nevertheless, it’s still an approach, a treatment, which is worth considering, particularly in people who, in whom the rate can’t easily be controlled with medication.

And can people have multiple cardioversions then?

They can. Some people have many attempts but the more attempts that fail, the more likely, it seems, that this is the wrong treatment for this person. And then there are other ways of restoring the rhythm or controlling the rate.

Dr Tim Holt explains how having AF can increase a person’s risk of stroke.

I think the risk that we worry the most about is the risk of having a stroke, which is significantly higher in people with atrial fibrillation compared with otherwise similar people who don’t have that condition. So if you have atrial fibrillation then the risk of having a stroke in the future is perhaps five or six times higher than if you didn’t have atrial fibrillation. So this is a particularly important condition to detect because there’s a lot of things that can be done to reduce that risk of stroke.

Have you seen any patients who’ve had AF related strokes?

Yes and sometimes this happens to people who are known to have AF and they have a stroke despite the condition already having been diagnosed. In other situations, the AF might be diagnosed when they’re admitted to hospital with a stroke and in other patients, a stroke occurs without there being any evidence, at that time, of AF but then in the future, the person is found to have AF, which is coming and going and was probably responsible for the initial stroke.

Dr Tim Holt explains how anticoagulants can help reduce the risk of stroke and suggests reasons why people might be reluctant to take them.

The risk of having a stroke, in people with atrial fibrillation, is significantly greater than people who don’t have that condition but, fortunately, that risk can be reduced very, very substantially by taking blood thinning medication, anticoagulants. However, there’s often a reluctance to use anticoagulants. Sometimes that reluctance comes from the patients, sometimes it comes from the doctor or sometimes it just comes from both through an anxiety over the thinning of the blood, the increased risk of bleeding, particularly in more vulnerable older people, who may be at risk of falls.

And which drug, in particular, are we talking about?

Well, any of the anticoagulants can raise the risk of bleeding but I think there is more concern over the usual drug, which is warfarin, particularly because that drug requires regular monitoring of blood levels to ensure that the dose remains appropriate for the individual. Because the dose is different for each individual, it varies between individuals and also varies from time to time within the same individual, so it’s important that it’s monitored. Of course, that’s an inconvenience to the patient because they have to have regular blood tests and they have to also comply with certain advice over their diet and other medications may interact with these drugs, which also influences the risk of somebody having a problem such as bleeding.

Dr Tim Holt explains the importance of managing warfarin levels through regular blood tests.

They need to manage the anticoagulation carefully in order that the, in the case of people taking warfarin, that the thinness of the blood is kept within the limit. That’s very, very important because the risk of stroke is there if the person is not taking warfarin or if the warfarin dose is too low but it’s also possible to have the other type of stroke, which is caused by a bleed into the brain, if the warfarin dose is too high. So keeping in close touch with the medical team, whether it’s the general practice or the specialist at the hospital, is important to keep the condition controlled and the stroke risk minimised in the in the long term.

Dr Tim Holt discusses the pros and cons of the new anticoagulants.

There are three new drugs that are used now. Dabigatran, rivaroxaban and apixaban and these are called the new anticoagulants and they have certain advantages over warfarin, most obviously that they don’t require you to have regular blood tests to monitor how thin your blood is because, by and large, the dose that you’re prescribed, provided it’s the right one for your age range, is likely to be the correct dose for all people in that group. So you don’t have to adjust the dose but the other advantage is that the limitations on diet, which, you know, the advice over restricting certain foods in the diet, which applies to warfarin, doesn’t apply to these other drugs. And so the person is more likely to be able to relax about that. However, they are new drugs. We still haven’t enough experience of using them to know for sure how safe they are in the long run. They’re not without side effects and they’re not without interactions with other drugs, so they need to be used carefully in selected people for whom there are problems with warfarin or people who are unable or unprepared to take warfarin.

As a doctor, Dr Tim Holt needs to keep up to date with the latest developments in AF so that he can help his patients.

It has been tricky for GPs because there has been an awful lot of policy change. There’s been change over recommendations over anticoagulants, over whether we should be screening people for AF, over what the best specialist treatment options are, who we should refer to specialists. So it’s easy to see how GPs have become a little bit confused at times over exactly what the guidelines are saying but there was a guideline published last year, in 2014, which has clarified this and it’s important that GPs keep up to date by reading such guidelines for any updates that occur from time to time. And, of course, we also keep up to date by reading medical journals, attending meetings, listening to specialists and engaging with the patient charities. Arrhythmia Alliance are very supportive of doctors, as well as patients, in keeping everybody up to date.

Dr Tim Holt believes there should be a balance between making people aware of AF without increasing anxiety.

Well, I think it’s important that people who are at raised risk of AF particularly, older people as they get older, don’t ignore it if they think that their heart rate is irregular. We have to also be careful that we don’t overdo it in the other direction and raise so much anxiety that everybody, you know, because everybody, at some stage in their lives could probably detect an extra beat or a feeling of thumping in the chest and we need to be careful that we don’t over investigate people. But, at the same time, it’s very important, in people who do have atrial fibrillation, that we detect it early. So it’s getting the balance right through raising public awareness of the need to seek advice if they have symptoms. And it’s also a good idea for doctors and nurses, who are checking people’s blood pressures or examining them, to just check that the heart rate is regular and, if it isn’t, to follow it up with an ECG.

Dr Tim Holt explains why aspirin is no longer considered effective in reducing stroke risk in people with atrial fibrillation.

It used to be advised that if a person either couldn’t take warfarin because it was considered for some reason unsafe or they simply declined it, then aspirin was considered to be a reasonable alternative, although it was always recognised that it wasn’t as effective as warfarin. However, more recently, it’s been discovered that, in fact, it’s not only much, much less effective and not really effective at all in reducing the stroke risk in people with atrial fibrillation, but it’s actually not that much safer than taking warfarin either, provided the warfarin can be safely and carefully managed and monitored. So aspirin as an alternative to warfarin is no longer considered a reasonable approach. It’s not as effective. It’s not really significantly effective at reducing stroke risk and it’s not completely safe either. It’s, you know, it can cause haemorrhages. It can cause internal bleeding and it can cause bleeding into the brain. So it’s now advised that people should be assessed over what their stroke risk is, people with atrial fibrillation, should be assessed over whether they are at risk of stroke and this applies to the majority of people with atrial fibrillation, they should be offered an anticoagulant, taking into account their bleeding risk. There are people in whom the risk of bleeding is too high and they shouldn’t be offered anticoagulants but the majority of people can have their stroke risk reduced substantially by taking an anticoagulant and these people should not be given aspirin in that situation.