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听BRITISH BROADCASTING CORPORATION
RADIO SCIENCE UNIT
CASE NOTES
Programme 2. - Arrhythmias
RADIO 4
TUESDAY 07/06/05 2100-2130
PRESENTER:
MARK PORTER
REPORTER: TRISHA MACNAIR
CONTRIBUTORS:
PETER WEISSBERG
RACHEL ADAM SMITH
STUART ALAN
RICHARD SCHILLING
GARY HUMPHRIES
BILL GROVES
SAMIR SHAH
KATHERINE PEEL
JOHN MORGAN
PRODUCER:
BETH EASTWOOD
NOT CHECKED AS BROADCAST
PORTER
Hello. Today's programme is all about cardiac arrhythmias - disturbances in the natural rhythm of the heart that cause everything from the occasional missed beat, to life threatening cardiac arrest.
Given that the average person's heart beats around three thousand million times during their lifetime - a feat that requires three billion perfectly synchronised contractions of the four chambers of the heart - it's hardly surprising that, occasionally, things go wrong.
HUMPHRIES
If there wasn't a defibrillator at the leisure centre that I'd played squash that evening I wouldn't be here today.
PORTER
More from Gary later.
My guest today is Professor Peter Weissberg, a cardiologist and Medical Director of the British Heart Foundation.
Peter, what's actually happening during a heart beat?
WEISSBERG
Well quite simply the heart has two upper chambers and two lower chambers. The upper chambers receive the blood either from the body or the lungs and the upper chambers contract and push the blood into the lower chambers, the upper chambers are called the atria, the lower chambers are called the ventricles and then the ventricles synchronously - that is together - contract to push blood out either into the lungs or to the rest of the body, depending on which side it is. So there's a wave of contraction from upper chambers to lower chambers to out.
PORTER
Because it's basically one big piece of muscle isn't it ...
WEISSBERG
It's a big pump, yes.
PORTER
So how does - what times the contraction and what initiates that contraction?
WEISSBERG
I thing called the pacemaker and the heart's driven by an electrical impulse. So if you imagine a little battery that's firing off about once every second in the upper chamber and it sends out a wave of electricity, a bit like dropping a pebble in a bath and you see those ripples moving out, that's the way - the electricity spreading through the heart muscle and as it spreads through the heart muscle so the muscle contracts as it arrives.
PORTER
And what's controlling the pacemaker, what determines - because obviously a heart beat varies tremendously depending on whether we're at rest, whether we're excited, whether we're exerting ourselves?
WEISSBERG
I mean the pacemaker has its own control and so if left to its own devices it would drive our hearts at about 80-90 beats per minute. We normally run at about 60 beats per minute when we're just relaxed and that's because the body has a way of putting a cap on the natural heart rate. When we need to have a greater output of blood from our hearts then that restraint is lifted by the body ...
PORTER
The brakes are taken off.
WEISSBERG
The brakes are taken off and the adrenaline pumps in and the heart speeds up.
PORTER
So what's happening when we get an arrhythmia - a disturbance in the natural heart rhythm - what are some of the more common causes?
WEISSBERG
The commonest cause is some sort of disruption to the electrical activity of the heart and there are a variety of reasons why this might occur. By far the commonest is an ageing heart that's been affected perhaps by the commonest disease which is coronary artery disease but hearts can either go too slowly because there's a disruption in the electrical pathways or they can go far too fast.
PORTER
Now it's normal to have the occasional irregularity, people might notice the odd missed beat ...
WEISSBERG
Absolutely.
PORTER
... nothing to worry about. What sort of things point to a more sinister cause that may warrant investigation and even treatment?
WEISSBERG
Well I think, as you say, people often feel a kick or an extra thump, they think it's a missed heart beat, and that's perfectly normal and not to be worried about. If, on the other hand, somebody gets a sustained prolonged episode where they feel their heart is pumping far too fast and far too hard, lasting for minutes to hours, then clearly that's something they should consider or if the sensation of irregularity of heart beat is associated with either chest pain or severe shortness of breath - those are the sort of symptoms that should make you think there's something going on that you should seek help for.
PORTER
Well Rachel Adam Smith was born with an abnormal heart and underwent major cardiac surgery as a baby - unfortunately that wasn't to be the end of her problems. As Trisha Macnair discovered when she met Rachel and her daughter Francesca.
ACTUALITY - MOTHER TALKING TO BABY
MACNAIR
Things sound very normal but it's been a rough path for Rachel in recent years. At 16 her heart started beating in an abnormal rhythm which caused episodes of palpitations and left her feeling breathless. The symptoms slowly got worse but weren't properly diagnosed until Rachel took advice before starting a family.
ADAM SMITH
The cardiologist informed me that I was in atrial flutter and said that he had to get me in within the next couple of weeks to give me a cardioversion, which is an electric shock to the heart to try and rectify the abnormality.
MACNAIR
But repeated efforts to get Rachel's heart back into a normal rhythm were unsuccessful. Eight attempts at cardioversion left her sore and shaken. Fortunately, drug treatments eventually did the trick and she felt better than she had in years - that is until she became pregnant and the abnormal heart rhythm returned.
ADAM SMITH
The heart went back up to 220 beats a minute, which was absolutely terrifying and the heart was going so fast that I could see it literally jumping out of my chest, I could feel the pulses in my neck and all over my body pumping. And a pain in my back and my chest and my arms. The machines were all bleeping, going off and it was just quite terrifying really. And they then said to me that it was time to have a pacemaker.
MACNAIR
It's nearly 50 years since the first pacemaker was implanted in a human body, and developments in technology have lead to huge advances in what these devices can do. Now there are three different types of pacemaker for the heart, depending on what the particular problem is. Dr John Morgan is from the Wessex Cardiac Centre at Southampton General Hospital.
MORGAN
First of all there are pacemakers that are intended to deal with slow heart rhythms, so the conventional pacemaker that most people would recognise and understand. There are diseases of the heart that cause the heart to beat slowly and there are no drugs that can compensate for that and so the heart needs to have some external stimulation source, but rather than having something that's external to the body you implant a device into the patient under the skin with the leads going down into the heart that then deliver electrical impulses that generate a heart rhythm because the heart's own systems don't do that. The second type of implanted device is a thing called an implantable defibrillator, this device is able to recognise when the heart goes too quickly and then it delivers a shock treatment to the heart to return it to normal rhythm. A third type of device then is a thing called cardiac resynchronisation therapy. And this is a relatively new concept and this therapy is applied to patients who've got impairment of the pump function of the heart and if you put in a pacemaker that is able to pace the different walls of the heart simultaneously it reconfigures the contraction pattern and makes it work better. So now we have a generation of pacemakers that are designed simply to improve the function of the heart muscle and nothing at all to do with the heart rhythm.
MACNAIR
The very first pacemakers were too big to be implanted inside the body and even as recently as the 1970s the defibrillating part of the pacemaker consisted of two large patches which had to be sewn directly onto the walls of the heart. But these days a lot can be packed into a tiny space and the devices are much more discreet.
ADAM SMITH
The pacemaker itself is about the size of a 50 pence piece and the scar is probably about an inch long and it's just above the chest, underneath the collar bone. There's no lumps, it just feels when you touch the actual pacemaker itself that you can feel the hardness underneath where the pacemaker is.
MACNAIR
Despite its small size, Rachel's pacemaker is an extremely smart gadget.
Mr Stuart Alan, Senior Chief Cardiac Physiologist on the Cardiac Rhythm Management Team at Southampton explains how these sorts of pacemakers can save lives by acting quickly and intelligently.
ALAN
What this device does essentially is to protect the patient from any abnormal heart rhythms, especially those that may be life threatening. So these wires pick up the electrical activity from the heart, the device processes it and decides whether this is going to be dangerous or not, if it is going to be dangerous it can do one of two things, it can try and, what we call, anti-tachy pace where it paces the heart very fast and that will then put the rhythm back to a normal rhythm or if the rhythm is going dangerously fast, typically over 250 beats a minute, what will happen then is the device will charge up and deliver a shock. So it does that internally rather than what would happen if you didn't have a device, you would have to wait for the paramedics to arrive and they'd do the shock externally on the chest. And typically of course if that doesn't happen in the first few minutes then you'd have brain death occur. Now this device will work in less than 10 seconds from the time they go into their rhythm to the time it delivers the therapy, it's typically around about 10 seconds. So sometimes the patient hasn't even collapsed or hit the deck by the time the device kicks in.
MACNAIR
The pacemaker stores data from events like these, providing a record of exactly what went on. This information can later be read in the cardiac centre to check that the pacemaker is working properly, and to reassure the owners that they are safe.
ADAM SMITH
Apparently I have had an episode of atrial tachycardia, which is a new one for me, another abnormal heart beat and apparently it happened whilst I was trying on shoes because I remember the occasion and I don't actually remember feeling anything, it lasted for about 10 seconds, and according to the pacemaker technician the pacemaker kicked in and told it off and we went back to normal.
PORTER
Rachel Adam Smith talking to Trisha Macnair
You're listening to Case Notes. I'm Dr Mark Porter and I discussing abnormal heart rhythms with my guest Professor Peter Weissberg.
Peter, how are pacemakers like Rachel's powered and what happens when you need to change the battery?
WEISSBERG
They're powered by a small battery which is an integral part of the pacemaker itself, the box is mostly battery actually and it's the size of a very small matchbox underneath the skin. And it's monitored, usually annually, to see whether the power is beginning to fail and once the technicians detect that there is a downward trend in the battery life then they'll recommend a replacement and that's a minor procedure to just replace the box.
PORTER
So you remove the whole pacemaker pretty much?
WEISSBERG
Well you remove the box but you don't remove the wires, the hard bit going into the heart is left - that's left alone.
PORTER
Peter, I want to move on to atrial fibrillation, better known perhaps as AF here, a lot of doctors talking about AF. It's the most common type of arrhythmia we treat in general practice, I suspect the most common type you see as well. What's going wrong and how does it differ from atrial flutter?
WEISSBERG
From the patient's perspective there isn't a great deal of difference between atrial fibrillation and atrial flutter, they're aware of their heart going too fast. The subtle distinction is that atrial flutter is a regular rhythm, with the heart beating at about 150 beats per minute and atrial fibrillation is a chaotic rhythm with the heart beating anything from 60 beats a minute to 200 beats a minute but in a very erratic and irregular way.
PORTER
I was taught when I learnt cardiology famously irregular, irregular pulse.
WEISSBERG
That's right, yes.
PORTER
What sort of symptoms - I mean we pick this up on an ECG, that's how we diagnosis atrial fibrillation, besides the irregular pulse what might the patient themselves notice?
WEISSBERG
Well a lot of people are unaware of having atrial fibrillation, as you'll appreciate ...
PORTER
It's extremely common isn't it.
WEISSBERG
It is very common, particularly as people get older. But they may be aware of palpitations, that's the sensation of their heart beating erratically and irregularly or they may just notice that they've suddenly become rather more breathless than they otherwise were but they don't - they're not aware of the fact that their heart is now beating erratically.
PORTER
Because if the atria are beating chaotically then they're not filling the main chamber of the heart, the ventricle, properly, so presumably that has a knock on effect on efficiency, the heart's not pumping as it should do.
WEISSBERG
It's not as efficient, that's absolutely right.
PORTER
But for most people with aortic they can sort of battle on with it, they can get on with it, they might not notice unless they're exerting themselves for instance, so why is of such concern to us?
WEISSBERG
The major concern about atrial fibrillation if people are not symptomatic, the first concern is if they're getting symptoms then we need to do something about it to get rid of the symptoms. The real risk though is that if the atria - the upper chambers - are not contracting regularly then they can form small blood clots and if one of those dislodges it'll shoot through the arterial system and at worst it may lodge in the brain and cause a stroke.
PORTER
And that's why there's this big thing about people with atrial fibrillation needing blood thinning products like warfarin and all that goes with it.
WEISSBERG
That's right.
PORTER
Briefly, looking at treatment, do we use drugs to treat atrial fibrillation?
WEISSBERG
Yes we do. We use warfarin to stop the risk of a stroke. And if the heart rhythm is too fast and causing the patient symptoms then there are several different drugs that we can use to slow the heart rhythm down. Once the heart rhythm's been slowed down then it actually doesn't matter if it's fibrillating, most patients can live a full and normal life ...
PORTER
So it's still fibrillating but at a decent rate?
WEISSBERG
That's right.
PORTER
And what about shocking the heart, we sometimes use that?
WEISSBERG
Yes, if somebody has severe symptoms from their atrial fibrillation then you do what's called a cardioversion, which is giving the heart an electric shock and this disrupts all of the chaotic electrical activity in the heart and allows hopefully the normal pacemaker to take back over and reset the heart rhythm.
PORTER
Well another way of dealing with atrial fibrillation - and related problems - is to identify the focus of abnormal electrical activity that's triggering the arrhythmia, and destroy it - a process known as ablation, the procedure performed on the Prime Minister Tony Blair last year.
Dr Richard Schilling, a cardiologist at Barts and the London Hospitals, uses 3D computer imagery to locate the source of the problem in the wall of the heart, and then access the spot via a wire and hollow tube - or catheter - passed up into the heart from a vein in the groin. Bill Groves is one of his patients.
GROVES
I actually took myself into casualty with symptoms which were then diagnosed with an ECG and then obviously referred to a consultant cardiologist at our local hospital who treated me at that stage with various different drugs which seemed to control the atrial fibrillation. The unusual heart beat did start to come back, despite the drugs, and it got to the stage eventually where I had this heart beat running all the time.
SCHILLING
Well ablation literally means destruction and what we're doing when we're trying to treat people's abnormal heart rhythms is to get rid of the electrical activity in the key bits of the heart that are causing their heart rhythm problem. And we do that by passing the wire up to the heart and then passing energy through the heart to heat up the tissue and that forms an inert scar, so it can no longer conduct electricity. We're actually manipulating the catheters at the bedside, so a catheter is a long thin wire that you can pass up to the heart through a very tiny incision, so they don't need to have any stitches after the procedure. So one of us operates the catheter at the bedside and then we have a whole team of people operating the computer systems allowing us to sort of direct the ablation. This involves us doing a CT of the patient, of their heart, a week or so before they have the procedure and then we're able to import the CT into our electrical systems and orientate it so it's sitting in exactly the same position as the patient is on the table and then we can move our catheters around in this 3D image of the patient's heart, so it means that we can do the procedure much more accurately and precisely than we would do before.
GROVES
It's a long procedure and in my case I was actually down in theatre for over eight hours. But the actual procedure is obviously uncomfortable but not painful or anything too distressing. In my case it was immediately obvious that it had been successful because actually during the operation where they use the radio waves my heart beat actually kicked straight back into a normal rhythm, which it hadn't been like for many years. Your heart beat is actually coming through some sort of speaker system so you can hear it going and of course all of a sudden it was just beep beep in normal rhythm and I thought was that me, you know.
SCHILLING
For atrial fibrillation we have to do quite extensive ablation to cure the problem. So a few weeks afterwards they get some inflammation and irritability of heart which can make them feel like they're getting a few palpitation, then it settles down to form an inert scar, which doesn't cause them any problem after that. The success rates for us are around 80% and a number of patients have to come back for more than one procedure. Now 80% doesn't seem like a lot but when you compare it to drugs which almost invariably fail then that's - for people that are in atrial fibrillation who are getting bad symptoms that's a huge change in their quality of life and you know they're prepared to go through anything to try and get it sorted out.
GROVES
I'm off all the previous drugs that I'd been taking for about 10 years. I've definitely got more energy. I certainly seem to be able to do more than I could before. I play regular golf, we walk a lot, we swim and keep fit and generally very active.
PORTER
Bill Groves. Mr Samir Shah, a cardiac surgeon at Leeds General Infirmary, uses a different approach.
Ablating the trouble spots from the outside of the heart via keyhole surgery through the chest wall. A procedure, he says, is more accurate than medical ablation and often more effective.
SHAH
The whole basis of this technique is to create an injury, a full thickness injury, to the heart muscle and then as that heals it forms a fibrous scar preventing the electrical activity from coming through.
PORTER
And that differs from medical ablation in what way because the impression I got was that's what basically they're trying to achieve as well - that they're damaging tissue?
SHAH
They are also trying to achieve the same thing but with the medical approach you're not absolutely certain that you're getting a full thickness burn and it's the full thickness that's important because even if you have some tissue that has not been injured present then the electrical activity can still get through.
PORTER
So if you're both using, for instance, radio frequency ablation, are you using a different type of probe and higher power or - why do you get the full thickness burn and they don't?
SHAH
Because we use - what we'd use, for example, in the tool that we have for radio frequency ablation is a tool that has - it's like a pincer and we can then have the muscle of the heart between the two pincers of the instrument and use a bipolar system to create a burn between the two arms of the actual tool.
PORTER
What about success rates compared to medical interventions, we heard there that a good result with radio frequency ablation they might be able to help 8 out of 10 people, how does that compare to your technique?
SHAH
Well the success rate depends on how - to a certain extent on how long a patient has had atrial fibrillation and the best success rate is achieved in patients who've got new onset atrial fibrillation or so-called paroxysmal atrial fibrillation ...
PORTER
Where it comes and goes.
SHAH
Where it comes and goes, exactly. And in those sort of patients you can get a success rate of up to 90%, anything between 70 and 90%. In terms of catheter ablation, again the key is whether you're getting these full thickness burns and whether you can get to all of the areas of the heart using a catheter, which is sometimes difficult. And so in the best case scenario you can achieve an 8 out of 10 success rate but if you don't achieve full thickness or get to all of the areas concerned then the success rate is much less, of the order of probably 40-50%. And the other issue is if you do create the wrong burn in the wrong place then the need to require a pacemaker afterwards is sometimes higher with catheter ablation.
PORTER
So this is the risk of blocking a healthy electrical channel, if you like, you might actually have to put a pacemaker in afterwards. Are there any other unwanted side effects, I mean if you're using the full thickness burn is there more risk during the procedure?
SHAH
Not with the current technology. The problem with the old cut and sew technique when people tried it was that obviously you are - you're cutting and sewing back areas of the heart and so there was an increased risk of bleeding afterwards. Whereas those side effects are far less in patients who have the radio frequency ablation done in an open way with the current technology.
PORTER
Samir Shah, talking to me from our studio in Leeds.
Peter, I don't want to get involved in a cardiologist versus the cardiac surgeon debate, suffice to say there's lots of different techniques out there.
It's an exciting area - if it works there's no need to take drugs, there's no need for doctors, nurses or patients to be involved in monitoring anticoagulants like warfarin but how widely available is this sort of surgery or medical ablation?
WEISSBERG
Well not very, is the immediate answer, and I think it does depend a little bit on the condition. Atrial flutter, is more amenable to this sort of therapy and ...
PORTER
The fast regular one we talked about.
WEISSBERG
It's a rarer form of rhythm disturbance, I have to say the minority of people that you and I see will have atrial flutter, most will have atrial fibrillation. When it comes to atrial fibrillation then of course there are a variety of underlying causes for this and some of those may make it very difficult to get somebody out of atrial fibrillation and we've just heard the longer they've been in it the harder it's going to be anyway. And I think we're on a learning curve at the moment trying to understand which patients respond best to either a surgical or a catheter based radio frequency ablation and we're learning all the time. Five years ago this really wasn't available at all, it's now available in specialist centres. If it really does turn out to be as successful as is claimed then clearly it will be rolled out into more centres.
PORTER
Let's move on a bit, I want to move on to more catastrophic arrhythmias when basically they're so bad that the heart stops pumping blood completely - a cardiac arrest. What's happening there?
WEISSBERG
Well there are two forms of cardiac arrest. The rarest is what's called asystole, when the heart just stands still, it doesn't pump, and that's usually as a consequence either of what we call heart block and there's just no electrical impulse going through to the heart at all or occasionally because the heart's suffered such a terrible heart attack that there's no live muscle left ...
PORTER
The blood supply's been destroyed.
WEISSBERG
That's - absolutely. And there's really not a lot one can do about that but obviously no one would know initially if somebody collapsed whether this was asystole or not. The commonest form is what's called ventricular fibrillation where the main chambers of the heart are not contracting at all, they're just wriggling around like worms and not pumping any blood out at all. And that would cause somebody to collapse. And that's the rhythm disturbance that responds very well to prompt action and cardiopulmonary resuscitation.
PORTER
This is the classic scene, isn't it, where anyone who's watched Casualty or ER or any of those programmes would have seen the defibrillator - the paddle machine.
WEISSBERG
That's right, yes.
PORTER
Now you often hear people describe this as jump starting the heart, that's not actually what's happening is it.
WEISSBERG
No it's not because what's happening in ventricular fibrillation is that you've got widespread chaotic electrical activity in the heart, nothing's coordinated. What you do with a defibrillator is you give an electric shock which affects all the heart cells, heart muscle cells, in the heart and they all stop for a split second ...
PORTER
It stuns them basically.
WEISSBERG
It stuns them in effect and you hope then what will happen is that the normal pacemaker rhythm will kick in and then take over and that's usually what happens provided somebody's treated very quickly.
PORTER
And we talked earlier about cardioversion - shock treatment for atrial fibrillation - and we're basically doing the same thing there aren't we.
WEISSBERG
Doing the same thing, except when we do cardioversion for atrial fibrillation it's usually done electively - that means we put somebody to sleep so that they don't feel the shock.
PORTER
It's planned and a bit easier.
WEISSBERG
Yeah.
PORTER
Well defibrillators may be a common site in hospitals and ambulances, but up until recently, you would not have found them at train stations, shopping arcades and leisure centres. Fifty-year-old Gary Humphries is one of at least 200 people thought to owe their lives to a new breed of defibrillator that doesn't need a paramedic, nurse or doctor to operate it.
HUMPHRIES
My name's Gary Humphries, age 50, I suffered a cardiac arrest playing squash 18 months ago in Hawthorne Leisure Centre, where I am at the moment. Well I was a little bit late arriving on the squash court, we should have started at quarter to five, just after work, I got on court about ten to five, so we started to warm up and he said to me it was probably about ten past five where he served a ball to my backhand on the court and I didn't hit the ball back and the next thing that he saw of me was I was just as stiff as a board and I fell back and hit my head on the squash court floor and then he put me in the recovery position and went to the reception and fortunately enough they had a defibrillator. Apparently they tried the CPR when they did come on court but I had stopped breathing and subsequently when they used the defibrillator they shocked me and when they had the ECG run of the defibrillator after they'd shocked me it showed that I'd been clinically dead for two minutes.
DEFIBRILLATOR
Connect electrodes. Stand clear. Analysing now. Stand clear. Shock advise. Stand clear. Push to shock.
PEEL
Having a defibrillator applied promptly, and we say within four minutes really, will make all the difference because for every minute lost the chances of survival are reduced by 14%.
PORTER
Katherine Peel, Head of Emergency Life Support at the British Heart Foundation - the driving force behind the campaign to get more defibrillators into the community. So where should they go?
PEEL
Transport centres such as railway stations, airports, shopping centres, football stadia - all those sorts of places. And really more and more defibrillators are being put in the community now but there is a great deal of room for improvement. The British Heart Foundation has itself put over 3,000 defibrillators already in community sites and with GPs and with an injection of lottery money we are now working with the ambulance services in England to put an additional 2,300 defibrillators in the community.
HUMPHRIES
All I can say is, is the night it happened to me in the Hawthorne Leisure Centre that defibrillator probably cost the British Heart Foundation and the leisure centre about 拢2-2,500. Can you put a value to a life at that price? I don't think you can. Should people be afraid using a defibrillator? With the experience that I've had on knowing what defibrillators are now, it talks you through, if the individual needs a shock the machine will tell you. So I don't see why people should be afraid. I've been working with the leisure services and the local health board and now they are having defibrillators placed in every leisure centre within Caerphilly Borough Council and that's some of the work that I've been trying to do to make people have a better chance like I actually had.
PORTER
Gary Humphries
And Peter, I can vouch for how simple they are to use, we use one in the surgery now - well not very often hopefully - and it really is very, very easy. We talked there about - Gary's obviously someone who's benefited from that but there was probably someone better known - Ranulph Fiennes did as well didn't he?
WEISSBERG
He did, he'd just boarded an aircraft in the South West when he suddenly collapsed with a massive heart attack and in ventricular fibrillation and the staff there had a defibrillator and defibrillated him straightaway so that he got to hospital and got his by-pass surgery. And as many of you will know he's just tried to climb Everest, which was a phenomenal feat.
PORTER
Professor Peter Weissberg, thank you very much. That's it for today. Next week's programme is all about blood clots, or thromboses - just how risky are long haul flights? And why low dose aspirin can be literally life saving for people with a relatively common, but little known syndrome that can cause headaches, forgetfulness, recurrent miscarriage and deep vein thrombosis?
ENDS
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