Atrial fibrillation – rate or rhythm control?

So if you have atrial fibrillation what’s the first thing that needs to be sorted?

In the absence of medicines or heart disease the heart races at over 150 beats per minute. This can feel very uncomfortable – a sensation the heart is racing combined with breathlessness and fatigue. If there are other heart problems such as coronary artery disease it can make these more troublesome and cause worsening chest pains.

Surprisingly some people don’t have any symptoms and it’s picked up incidentally! If untreated this can cause the heart to wear out – the ventricles contract more weakly – a condition called tachycardia cardiomyopathy.

So the first goal is to reduce the heart rate. This can be achieved by medication – beta blockers, calcium channel blockers or digoxin. These all slow conduction in the atrioventricular node and therefore slow the ventricular rate.

But rewind a bit – if the atria are fibrillating, shouldn’t we fix it?

Well, yes, that is the logical thing to do. But being cardiologists we are not satisfied with mere logic, we want evidence.

It is relatively simple to reset the heart from atrial fibrillation to normal (sinus) rhythm. In fact in many people the fibrillation lasts less than a day, but these episodes (or paroxysms hence the term paroxysmal atrial fibrillation) have a tendency to become more frequent and last longer before becoming persistent.

At the turn of the century cardiologists performed a trial to test if patients did better with a rate control strategy or with a rhythm control strategy. This was the AFFIRM trial which published in 2002. This landmark study of 4060 patients showed that there was no benefit to a rhythm control strategy compared to a rate control strategy. In fact, there was a trend towards a lower death rate in the rate control group (but statistically this did not reach significance). Quality of life was assessed and not found to be different between the 2 groups but the method of assessing this and the results are not quoted in the original paper.

This has led to guidelines recommending rate control as the initial treatment strategy. But there are important caveats to this. The trial only enrolled patients above the age of 65, so it’s findings are not applicable to younger patients. Secondly, the use of anticoagulants to prevent stroke was a little worse in the rhythm control group at around 70%, compared to the rate control group at 83%, because the trial protocol allowed for discontinuation of anticoagulation in the rhythm control group. This may account for inferior outcomes in the rhythm control group. Finally, of course, our treatments for rhythm control have expanded since 2002 (the subject of a future post)

In the AFFIRM trial only a single patient in the rhythm control group underwent ablation of atrial fibrillation (the seminal paper which described this was only published in 1998) which has become an important tool in the intervening years.

So we know that rhythm control or rate control with medicines are equivalent options in the treatment of atrial fibrillation when it comes to hard outcomes like death rates.

But that’s not to say there aren’t symptomatic improvements with rhythm control. This is where it is important to see an expert to tailor the treatment strategy to you personally as opposed to what’s good the population. A good doctor will explain all the options for treatment strategies for rate or rhythm control, anticoagulation and the importance of lifestyle factors, discover what goals are important to you and help you achieve them.

Atrial Fibrillation – an introduction

Lots of people come to see me with atrial fibrillation or AF as it’s often known.  While they might have been given a diagnosis, they often haven’t had time to discuss the implications and options for treatment.

The problem is that Atrial fibrillation is both incredibly simple and quite complex at the same time.

When I asked one of my junior doctors to do a presentation on it – he said that would only take half an hour, not realising that you could easily write an entire textbook on the condition!

So here is some useful information as a starter – there’ll be some follow up posts in the coming weeks.

The heart has 2 atria and 2 ventricles.  The atria collect blood from the body and pump it into the ventricles which then pump blood around the lungs and the body.

Latidos

In atrial fibrillation the atria don’t pump properly – the electrical activity in the atrium is chaotic rather than regular and this means the tissue is writhing rather than a coordinated pumping.

This leads to two consequences.

Firstly, the atrioventricular node (shortened to AV node), the only normal electrical connection between the atria and the ventricles is bombarded by the chaotic electrical activity of the atrium at over 300 times per minute.

Fortunately it can’t work that fast, but it will be activated and trigger the ventricle irregularly at usually between 150-230 beats per minute.

This means the pulse is fast and irregular.  Not all the heart beats can be felt in the pulse at the wrist because the heart may not have enough time to fill properly and therefore the ventricles may not pump a lot of blood with every heart beat. Feeling the heart beat itself on the chest or the pulse in the neck is probably a better way of working out the heart rate.  But to clinch the diagnosis, an ECG (electrocardiogram) is needed.  This can even be done using smartphone or smart-watch accessories!

Secondly, because the atria are not contracting properly in a coordinated way, blood can stagnate within the atria and form clots, usually in part of the atrium called the appendage.  Not really a problem if the clots stay in the atrial appendage, but if a bit breaks off, it can cause a stroke.  This is one of the commonest causes of strokes and it actually tends to cause worse strokes than other causes.

So the initial treatment of atrial fibrillation focusses on controlling the ventricular rate and on assessing the risk of stroke.  That will be the subject of another post!

 

His Bundle pacing

This is a really funny name.

It makes no sense to anyone except Cardiologists who remember that there was a person who identified a bundle of specialised conduction tissue within the heart.  That person was Wilhelm His Jr, hence the name “Bundle of His”.

It is pronounced Hiss rather than Hiz, by the way.

So what’s all the excitement about?

Well the Bundle of His is part of the normal wiring system of the heart and is responsible for carrying signals from the atrioventricular node down to the ventricles.

We have learnt that even in patients whose atrioventricular node doesn’t work properly, we are able to pace the Bundle of His and stimulate the ventricles via the rest of the normal wiring system.  This looks very pretty on an ECG!

This has been very challenging to do in the past, but newer techniques have made it more feasible.

Observational data from 765 patients in the USA has demonstrated that this is a safe and feasible technique, and suggests that it reduces the combination of death, heart failure or an upgrade to a more complex pacemaker.

This is only observational data, but there is growing evidence to suggest it might be better and worth a proper randomised study.

I’m pleased to be offering His bundle pacing to my ICD patients as part of the Hope-HF study for which I’m a Principal Investigator.  This is a study coordinated by Imperial College, London and I performed the first His bundle pacing in Medway last year.  It’s too early to know if it’s helpful in that population, but I’m sure we will see more interest in the pacemaker population in the coming yearsHis Bundle Pacing Electrogram

Conference season

So it’s March and conference season has begun.

In the world of cardiology there is a rhythm to the year with major announcements being made at the large American and European conferences, and smaller trials being flagged at the subspecialty conferences.

The American College of Cardiology meeting was earlier this month, with major news about the PCSK inhibitors (new fangled drugs for cholesterol) and news regarding His bundle pacing (see separate post).  I didn’t get to go, but kept up to date by the bloggers at the conference in particular Dr John Mandrola from the heart.org, as well as the ACC and ESC video coverage.

I did get to go the European Heart Rhythm Association meeting in Barcelona.  I was pleased to win a grant from the European Society of Cardiology to fund attendance.

It was a small meeting which meant is was easy to get around and go to interesting sessions by the greats in Electrophysiology.  Particularly good were the prize lectures by Dr Johnathan Kalman on atrial arrhythmias and Dr Josep Brugada of the eponymous Brugada syndrome about the genetic basis of rhythm disorders.

It’s a fantastic way of keeping uptodate with the latest developments in the specialty, and to network with colleagues across Europe – I met co-investigators for some of my research studies from Poland and the Czech republic as well as the UK.

Fitbit – curse or cure?

I’ve seen a few patient now because they’ve been worried about their Fitbit heart rate reports.

The Fitbit is an amazing bit of kit that can constantly monitor your heart rate. It’s worn on the wrist and is a step up from the older chest strap monitors that are widely used in sport, mainly because their convenience means they can be worn all the time.

This means the Fitbit is generating huge amounts of data on heart rate that we simply have never seen before as doctors. We’ve had the ability to accurately record continuous heart rate and ECG monitors for some years but these are complex devices put on by medical professionals and simply aren’t as widely used as a Fitbit. They are also mostly used in people with a high probability of heart rhythm problems rather than the healthy fitness focussed population.

Some people who feel well otherwise may see their heart rate is outside the normal range and unsurprisingly worry about it.

Most people who see me are worried that their heart rate is too slow at times. They can google it and find lots of information about fast heart rates but not necessarily slow heart rates.

Most people will have nothing to worry about, especially if they have no symptoms like feeling faint or fatigued; and if their heart rate goes up normally with exercise.

There are diseases such as sick sinus syndrome or heart block that can cause slow heart rates – these usually are picked up because of fainting or a constant very slow heart rate in the 30-40’s. This can be successfully treated with a pacemaker. More difficult is people who have a generally slow rate even on exercise – something known as chronotropic incompetence which can also be treated with a pacemaker.

Constantly rapid heart rates are worth investigating – some rhythms such as atrial fibrillation or slow atrial tachycardia can occur without symptoms and cause impaired heart function simply as a function of a rapid rate (over 100beats per minute) for weeks on end.

So the Fitbit is a helpful piece of technology which can certainly help to motivate and inform exercise programs. I’m sure it will pick up people who do have concerning heart rhythm problems but this will be a rare event!

Radiotherapy for Ventricular tachycardia

An amazing article in the New England Journal of Medicine this week.

This is the preeminent medical journal across the world. They’ve just published the experience of 5 patients who had radiotherapy to treat ventricular tachycardia.

Ventricular tachycardia is a dangerous heart rhythm disturbance that is most frequently caused by electrical short circuits around scar tissue in the heart. The heart can go very fast and not beat efficiently.

Most patients get a defibrillator to prevent sudden death, but this doesn’t prevent the tachycardia from happening – it just deals with the consequences.

Usual treatment is medications – where this fails ablation can be used. This involves putting wires into the heart to deliver microwave energy to burn tissue around the scar that is not working properly but can conduct electricity. This (hopefully) prevents the short circuit in the heart.

Problem is we can get to the muscle on the inside the heart and outside the heart but can’t easily deal with the muscle in-between.

These procedures take 4-8 hours under a general anaesthetic and can be very risky – my last patient we thought had a 20% risk of death from the procedure (he did ok and got home!)

This new method is completely different. An electrical map of the heart is created using an ECG vest and a CT scan that locates the scar. Radiotherapy is delivered around the scar and the procedure takes minutes. It takes time for the cells to react and the procedure to work but these patients had their ventricular tachycardia practically disappear.

Now there are lots of questions to answer about this – larger trials are needed to see if it really does work so well, how long it lasts, if there is collateral damage to the rest of the heart or organs but this is potentially a game changer in the field. You can see why it got published in the top journal. Here’s hoping it develops well and works out because it could transform our care of these patients.

High blood pressure – just got higher?

So the big news this week is that the American Heart Association has just released new guidelines.

What does that have to do with us? Well the UK and European guidelines all look at the same research studies and no doubt they will be updated soon.

The new guidelines define high blood pressure as greater than 130mmHg systolic and 80mmHg diastolic.

This is lower than before but the guidance on labelling and treatment is a little more complicated. Essentially if there are any risk factors such as being older or having diabetes then we should aim to get down into the normal range.

This is supported by the Sprint trial which was published in 2015, which actually suggested lower pressures of down to 120mmHg were better still, but given the fact that trial populations are quite tightly controlled he guideline committee went for a higher target for the general population.

The bottom line is that we should all look at our blood pressure and try to manage our weight, salt intake and exercise to keep the pressure normal. Many people will need medications also to help keep in a normal range and stay hale and hearty for longer!

What does systolic and diastolic mean?

The heart pumps blood every beat – so the systolic blood pressure is the higher number just after the heart contracts, and the lower number is the diastolic pressure which is what the pressure falls too when the heart is relaxing and the valves are closed to prevent blood rushing back to the heart.

mmHg??

The unit is a millimetre of mercury – that’s right – blood pressure was first measured by connecting a column of mercury to the arterial circulation of dogs and horses to see what height it would rise to (Poiseuille, 1828)! They needed a denser and so heavier fluid than water to fit in a column. We still use the units today – there was a push to change to SI units – kilo pascals but it never took off.