4 July 2018
More than 1.5 million people a year in the UK experience heart rhythm problems (arrhythmias). They can result in the heart beating irregularly and faster than normal, or more slowly, and beating in an abnormal, disorganised way.
As clinicians in electrophysiology, we only do two things. One is find the source of abnormal electrical activity in the heart and, very precisely, destroy the diseased tissue causing it.
The other is to find the path of an electrical circuit which goes around and around the heart chasing its own tail, in which case we try to break that loop by interrupting its course.
That’s all we do!
An emerging service
When I joined Harefield Hospital in 2002, there was no real arrhythmia service to speak of, although one had been set up at Royal Brompton Hospital by Drs Jonathan Clague and Jan Till. Neither of the hospitals had 3D mapping technology, which is where a map of electrical activity is created on a virtual three dimensional model of the patient’s heart.
The history of 3D mapping goes back to the mid-90s and models were beginning to be commercially available later that decade. The technology came to the UK relatively late, but there were examples of early adoption for research, including at St Mary’s Hospital where I worked with colleagues in the 1990s.
In 2006, I was made the Trust’s lead for the arrhythmia service, and we made a number of key appointments, including Drs Tom Wong and Sabine Ernst, and further invested in catheter labs and 3D mapping systems.
We now have no fewer than five electrophysiology labs for patients with arrhythmias: three at Royal Brompton Hospital and two at Harefield Hospital. Each of these has the full range of latest technology, with at least two, sometimes three, 3D mapping systems in each one.
The service has grown tremendously – we’re one of the two largest arrhythmia services in the UK – and we have made a huge effort to develop the expertise we offer: investing in people, investing in technology and investing in research.
In the days before 3D mapping, you had to use your brain to imagine and reconstruct in your mind, the source and path of abnormal electrical signals. Clinicians would use x-rays to give them a black and white, two-dimensional picture, and use their own knowledge and expertise of how catheters move in three-dimensional space to try and predict where that signal was coming from.
3D mapping systems changed everything. For the first time, they allowed us to reconstruct a 3D computer model of a chamber of the heart, and to then model electrical activity within it. So, doctors can now look at a map which clearly demonstrates how an electrical wave moves from A to B to C to D and see each of those precise locations.
For simple arrhythmias that follow a predictable path, we have no difficulty whatsoever in treating them. But our hospitals are about so much more than that; and having the latest 3D mapping technology allows us to treat problems of increasing complexity.
The next challenge has arisen from the need to treat atrial fibrillation (AF), by far the most common arrhythmia – looking at lifetime risk, it will affect a quarter of men, and a fifth of women, over the age of 40.
Some people with AF, those without symptoms, just need their risk of stroke reducing with blood thinning medication. On the other hand, some people have symptoms which are so severe they can’t go about normal activities in their daily lives, and we have to treat them. We often use medication first and if that’s not successful, we offer ablation.
Cardiac catheter ablation
Catheter ablation is a procedure that interrupts abnormal electrical circuits in the patient’s heart by destroying the diseased area. When the source of the abnormality is found, an energy source, such as high-frequency radio waves that generate heat, is transmitted through one of the catheters (thin, soft wires) to destroy the tissue.
AF ablation started in 1998 in Bordeaux in France, and we were one of the first centres in the UK to offer it as a treatment. We now do something in the region of 900 ablations for AF a year.
The first decade was really about making these procedures safer, quicker, and more comfortable for patients. But there is a ceiling of what clinicians can achieve in terms of success rates – depending on the type of AF, they vary between 50 and 70 per cent, meaning patients can require repeat procedures.
Atrial fibrillation and the limits of technology
Today’s care involves offering personalised treatments, tailored for individual patients.
AF is extremely difficult to map within the atria. Unlike stable arrhythmias, atrial fibrillation constantly changes so clinicians can’t use conventional mapping technology.
In AF, the heartrate in the patient’s atria will be something like 500 beats per minute, eight beats per second, but none of them are similar: they change by the millisecond. This has taken innovative approaches to mapping, stretching technology to its limits.
I’m extremely proud that we have two key mapping systems, one from a start-up company and one from a leading company where our close collaboration with industry over the last 5 years has helped develop an AF mapping platform. It’s this sort of technology which will stand us in great stead for the next decade – kit that will give our clinicians clearer pictures than ever before and, I am sure, greatly help patients.
The mapping systems are now so sophisticated, able to deal with so many electrical signals simultaneously, that they require powerful computers and sometimes separate workstations to process the data and send it back to the catheter lab in real-time, so that clinicians can treat the patient.
At Royal Brompton Hospital we have the only remote magnetic navigation lab in the country, and one of the labs at Harefield has a robotic system – the Hansen robot. There isn’t another NHS trust in the UK that can offer both.
Life before ablation
We have been very lucky in the UK because we’ve had some outstanding minds who first described atrial fibrillation with very little technology.
Drs Ralph Mines and Thomas Lewis described AF, including the details of its mechanics, as far back as 1914 and 1918 respectively. They understood it, primarily with their vision and imagination, and the very limited mapping technology available at the time. They were remarkably, incredibly accurate in their description.
But before ablation was available as a procedure, if people didn’t respond to medication there were only two types of treatment. One was to destroy the ‘cable’ that connects the atria to the ventricles of the heart and implant a pacemaker, so at least the ventricles received a steady pulse from the pacemaker, rather than the abnormal rhythm from the atria. But this didn’t resolve the fact that the atria were still out of rhythm, the contraction of the atria was still lost, and the risk of stoke still continued. It was a palliative procedure, it wasn’t a cure.
The only intervention that could be, potentially, curative was an extensive form of open heart surgery, called the Maze procedure, which required expert hands and which very few people around the world could do reasonably safely. It involved literally cutting up the atria into multiple pieces, and stitching them back together: the abnormal electric currents could not move between the scar tissue of the pieces that had been sewn back together.
The procedure carried a 3 per cent mortality in expert hands. Modifications of this technology, without cutting the heart but using radiofrequency or cryotherapy, sometimes minimally invasively, can still be helpful for some patients and indeed evaluation of this technology is the subject of a large randomised trial we are completing with help from the National Institute for Health Research.
There is a huge opportunity for the NHS to get better at how we treat patients with AF, especially in preventing people developing it in the first place: for example, by tackling obesity and high blood pressure.
Making sure GP practices know which of their patients have AF, and who among them are at risk of having a stroke, so they can have the appropriate blood thinning medication, is an exercise that is incomplete both in London and nationally.
We’ve been working to try and influence that on a wider basis, and we’re also working with our community pharmacists to identify patients with AF, so they can be given the right care. We are also working within the region to improve how patients are referred between GPs, hospitals and specialist care.
Technology will give us a huge opportunity: already patients can monitor their heart rhythm on their phone, meaning they can maintain a link with us, sending us their cardiac information as they go about their daily lives – this is something clinicians a few decades ago could only have dreamed of.
The same goes for patients with pacemakers or implantable cardioverter defibrillators: we’re able to receive information constantly, without them coming to an appointment – enabling us to look after a far wider group of people, where geography really doesn’t matter.
One of my patients was on holiday on a Greek island, and he called me and said, ‘I didn’t feel very well last night, I think I might have had a rhythm problem.’ He has a home monitoring device which he takes everywhere, so he just sent a transmission and I could immediately look into his heart rhythm events and advise.
This is already established, and offers just a glimpse into what the future of what we may be able to offer patients could look like.