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.

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