Restoring the Rhythm . . . Atrial fibrillation under the scope

Author: Dr Hitesh Patel

The global burden of atrial fibrillation remains unknown, but in New Zealand it is estimated that AF affects a minimum of five percent of the population. Atrial fibrillation is touted as the most common cardiac arrhythmia and complications can be severe – increased risk of stroke, heart failure, myocardial infarction and dementia. Management of atrial fibrillation involves initiation of oral anticoagulation, and interventions to maintain sinus rhythm or a rate control strategy – neither are without their challenges.

When atrial fibrillation is associated with a cardiomyopathy, it can be difficult to pinpoint the contribution of the high heart rate. Here Dr Hitesh Patel briefly touches on the ins and outs of decision making and medical means for patients suffering with AF.

Atrial fibrillation often goes hand in hand with other heart conditions – including aortic stenosis. After aortic valve replacement, for example, “a percentage of patients will develop heart block – a percentage will get left bundle branch block – whether they have TAVI or surgical aortic valve replacement,” explains Dr Patel.

Maintaining sinus rhythm is not possible in a large proportion of AF patients. Rhythm control refers to attempts to maintain sinus rhythm, rate-control refers to acceptance of atrial fibrillation and attempts to control the heart rate.

In short . . .

Rhythm Control:

  • Use of anti-arrhythmic drugs and/or electrical cardioversion to maintain sinus rhythm.
  • May involve catheter and/or surgical ablation.

Rate Control:

  • Involves the use of beta blockers and calcium channel blockers and digoxin to lower heart rate and limit symptoms. At times the anti-arrhythmic drug amiodarone is also used to assist with rate control even if it does not maintain sinus rhythm.
  • In those in whom rate control cannot be attained on rare occasions the AV node can be ablated, this blocks all electrical impulses from the atrium to the ventricles, in other words results in complete heart block, and renders the patient dependent on a pacemaker.

“We have a patient who was treated for aortic valve stenosis. She started off with good LV systolic function and had a TAVI procedure for severe AS, but within weeks she became short of breath and was in atrial fibrillation and she had developed wide QRS left bundle branch block. So, we questioned ‘What should we do?’” says Dr Patel.

“How much of the deterioration of her symptoms is because she has atrial fibrillation which is poorly controlled, how much is due to left bundle branch block related dyssynchrony?” There was discussion about electrical cardioversion, some were concerned that sinus rhythm could only be maintained with use of amiodarone and this in turn, since there already was left bundle branch block, could result in complete heart block and need for pacemaker.

“We talked about a resynchronisation device and we performed a Holter monitor on her – her average heart rate is 78 beats per minute. So, that’s a problem,” explains Dr Patel. “It’s a problem because if we implant one of these resynchronisation devices, she is not going to use it very much.”

“For cardiac resynchronisation devices to work, you have to be pacing more than 90% of the time, so we cannot put one of these things in her because it is just not going to work 90% of the time,” says Dr Patel. “There is no point putting a resynchronisation device in her with atrial fibrillation, unless we slow her heart down a lot.”

The case for agents

One way to slow down the heart is with the use of medical agents – such as amiodarone. However, whilst amiodarone has been successfully shown to block the potassium channels, it can also have adverse side effects – blocking sodium channels and beta and alpha-adrenergic receptors – which may increase mortality.

On the topic of amiodarone, Dr Patel says his patient wasn’t so keen to try it. “I spoke with her about going on amiodarone but she found it very hard to make that decision, so her treatment plan is still a work in progress.”

 Amiodarone can be used to maintain sinus rhythm. Findings from a multicentre trial ‘Amiodarone to prevent the recurrence of atrial fibrillation’ published by the New England Journal in 2000, found amiodarone more effective for the prevention of recurrences of atrial fibrillation than sotalol or propafenone.

The study analysed 403 patients – 201 assigned to amiodarone and the remainder to either propafenone or sotalol. At a 16-month follow-up, 35% of the patients treated with amiodarone and 63% those treated with sotalol or propafenone had a recurrence of atrial fibrillation.

It takes commitment

Successful treatment of atrial fibrillation depends on not just the treatment, but the patient’s commitment to treatment.

“We have one patient in his early 50s found to be in atrial fibrillation and in heart failure, but had no significant coronary disease,” says Dr Patel. “Initially, he was on maximum therapy for rate control– high dose beta blocker, diltiazem – and his ejection fraction was between 35 to 40%.”

The question begged, did he have cardiomyopathy with atrial fibrillation or largely a rate-related cardiomyopathy because of his atrial fibrillation?

“The challenge thus was how I can take this man who has had atrial fibrillation for months and months and try and sort it out?” explains Dr Patel. “Given his atrium is dilated, if I was to do a DC cardioversion on him, his chance of staying in sinus rhythm for any length of time wouldn’t be very high.”

However, AV node junction ablation – ‘ablate and pace’ – to control heart rate can also be considered as a last resort but this will cause complete heart block with a regular slow escape rhythm, and a pacemaker needs to be implanted.

 “So, destroy the AV node, stop the atrial fibrillation electrical impulses crossing the AV node, and then put in a biventricular pacemaker,” explains Dr Patel. “This is a big step for our male patient as we’re still unsure as to whether he has rate-related cardiomyopathy or if he has largely a non-ischemic cardiomyopathy. So, what to do?”

Given that 20% of patients with chronic atrial fibrillation will revert to sinus rhythm when treated with amiodarone, I said “Let’s put you on amiodarone,” explains Dr Patel.

After carefully explaining to him the potential for drug side effects he agreed to take amiodarone and he did revert to sinus rhythm – his heart rate was 58 beats per minute and his ejection fraction improved markedly.

“Fortunately, in this instance, we proved that this patient was actually suffering from rate-related cardiomyopathy,” explains Dr Patel. “Unfortunately, he stopped taking his amiodarone, so now he’s back in atrial fibrillation.”

So, what does the future hold for such a patient?

We have proven that this patient has rate-related cardiomyopathy. So, the potential to do pulmonary vein isolation cannot be dismissed, even though the chance of success with pulmonary vein isolation is much less in people who have had chronic AF.

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