Emergency Cardiology: Management of AF

In September, I, along with a number of emergency physicians from Adelaide and other twitter followers of Amal Mattu, attended the second Emergency Cardiology Update held in Melbourne.

The conference consisted of a series of quickfire lectures from a range of emergency physicians and cardiologists, with cameo appearances from haematology, intensive care and cardiothoracics. Each session had a number of learning points and tips on practical clinical management. I also took away a number of ideas on how to teach some of these concepts, inspired by Amal's approach.

I thought I'd share a few of these points for each of the lecture, starting with the first lecture of Day by Peter Kistler, head of clinical electrophysiology at The Alfred. This talk had a few good points and gets a post of its own, others I may summarise together in the coming days.

AF Management

The big debate of AF management remains in rate vs rhythm. Evidence shows that both approaches have the same outcomes, although there may be more drug side effects in the rhythm control approach. Conversely, rhythm control may improve LVEF, so should be considered in heart failulre patients.

That said, rate control remains the mainstay for most patients. Comparing target heart rates, there are equal outcomes for a strict (<80bpm) compared to a lenient (<110bpm) target, with similar heart rates achieved at 18 months.

Rhythm Control

Half of paroxysmal AF patients will revert spontaneously within 48 hours, and then up to 40% will remain AF-free for 5 years.

The drug therapies for rhythm control to consider are:

  • Sotalol - one of the most common in use, but is better at maintaining sinus rhythm, and not so good for achieving reversion
  • Flecainide - probably the most effective agent, but use is limited by the need for preceding echo and stress test to ensure no structural/ischaemic disease. One caution is that by slowing the atrial rate, this may allow the AV node to start to conduct 1:1, and you may end up with a paradoxical increase in ventricular rate. To prevent this, give it with an AV blocker as well
  • Amiodarone - is not so great for AF, but may be considered in structural heart disease
  • Vernakalant - is not yet available, but will likely be soon. It is an atrial selective agent and achieves reversion of AF in a mean time of 11 minutes. That sounds almost too good to be true.

When considering DC cardioversion:

  • 80-90% success rate, although there may be a higher success rate with paddles versus adhesive pads, and this statistic may reflect this prior practice
  • 200 joules may be required
  • AP pad placement is more effective

Be aware that medical cardioversion carries the same thromboembolic risks as DC cardioversion. The European guidelines recommend for any cardioversion:

  • A 48 hour time limit from onset without anticoagulation (recognising the optimal period may be far less, even down to 12 hours)
  • Routine use of heparin bolus for cardioversion
  • 4 weeks of anticoagulation for risk calculated by CHADS-vasc then review for ongoing use. This covers the post-cardioversion period of atrial stunning to allow for return of atrial mechanical function

In terms of anticoagulation:

  • Use the CHADS2-vasc score for risk stratification
  • Aspirin is likely ineffective to prevent thromboembolic complications, so consider anticoagulation for a score of 1
  • Use the HAS-BLED score to assess risk
  • The benefit of anticoagulation in AF is not ouutweighed by the risk of falls in elderly. One estimate is that more than 100 falls per year would be required to outweigh the benfits (given the unlikely outcome of an intracranial bleed per fall)

Ablation

I learnt some pathophysiology about AF. The pulmonary veins are the trigger point in most non-valvular AF, and ablation can be used to electrically isolate the pulmonary veins from the atrium. Because it's not great to diathermy circumferentially around the entire vein, there is a 30% reconnection rate. The next big step in ablation will be cryo-ablation using an endovascular balloon.

Take-home points

The key things I took away from this one were:

  • Rate control is the go-to for most patients with AF. Rhythm control should be considered if they are symptomatic in rate-controlled AF or have significant heart failure
  • Flecainide is a great agent for gaining rhythm control, as long as you know the heart is otherwise normal. Give it with an AV blocker. Sotalol is good to maintain control
  • DC cardioversion is quite effective. We should be using routine heparin bolus in doing so and then anticoagulating for at least 4 weeks after according to CHADS-vasc risk to cover the period of atrial stunning
  • It takes a lot of falls per year to overcome the benefit of anticoagulation

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