Atrial Fibrillation

I started this morning innocently reading a recent blog post by the St Emlyn's Team with the intention of screening large numbers of recent blog posts as part of my weekly CPD update. Low and behold, it is 5pm and I am still stuck on this one post and topic: ATRIAL FIBRILLATION. I should have known reading something about AF would not be a simple task!

I am sure I am not the only person who feels a little overwhelmed from time to time when faced with decision making in the management of AF. I guess it is because it does not fit in a neat box of a single answer for every event. 

I thought I would summarise a few key points I have reviewed today:

1. Definitions

• Atrial Fibrillation (AF) is an atrial tachydysrhythmia characterised by predominantly uncoordinated atrial activation with consequent deterioration of atrial mechanical function.
• The p waves which represent depolarisation of the atria, are absent during atrial fibrillation and the heart rhythm is irregularly irregular.​
• Correct description is AF with fast / slow / controlled ventricular response

2. Aim of treatment

• Prevent complications (thromboembolic events - stroke)
• Alleviate symptoms (minimise circulatory instability)

3. Priorities

• Assessment of time of rhythm onset 
  • It is important as it allows the clinician to determine whether a rate or rhythm control strategy is in the patient's best interest.
    ​A safe time frame for rhythm control (cardioversion) is 48 hrs from onset.
• Assessment of precipitating events
  • 'PIRATES' 
    • ​PE; Ischaemia; Resp disease; Atrial enlargement; Thyroid disease; Ethanol; Sepsis
  • Where there are identifiable precipitants of atrial fibrillation they should be treated.
  • There has been shown to be a 6 fold adverse event rate when treating AF secondary an acute underlying medical illness in the ED.
  • ​AF usually improves / resolves if treatment is directed at precipitant.
• Assessment of haemodynamic consequence
  • Most pts with AF are CV stable
  • ​2 uncommon groups may become unstable
    • Poor LV function
    • AF with rapid ventricular response > 150 bpm
• Assessment of stroke risk
  • Formal stroke risk assessment using the CHA2DS2-VASc score
    • ​Consider anticoagulation for men with a CHA2DS2-VASc score of 1
    • Offer anticoagulation to people with a CHA2DS2-VASc score of 2 or above
  • Bleeding risk should be assessed using the HAS-Bled Score​

4. Management

RATE CONTROL vs RHYTHM control

• AFFIRM Trial (2002): showed no benefit in rhythm control vs. rate control in terms of morbidity and quality of life, but patients deemed not likely to tolerate being in AF were excluded from the study (thereby negating any possible benefit shown in these patients).
• 40-70% of patients will spontaneously convert back to NSR at 24hrs
• Early or delayed cardioversion in recent onset AF NEJM (2019): In patients presenting to the emergency department with recent-onset, symptomatic atrial fibrillation, a wait-and-see approach was non-inferior to early cardioversion in achieving a return to sinus rhythm at 4 weeks.
• Which patient would you treat with rhythm control in the ED?
  • ​stable, low risk for short term stroke
    • clear onset < 48hrs
      • Immediate anticoagulation in ED not always required but should be considered in those deemed high risk for stroke as per the CHADS2VASC score.
    • > 3 wk of NOAC / therapeutic Warfarin
  • ​​If onset >48 hrs and ≥ 2 CHADS-65 criteria: consider rate control or TOE-guided CV
  • treatment options
    • ​electrical (150J biphasic)
    • chemical
      • ​Flecainide
        • ​If no underlying structural heart disease
        • IV or PO
      • ​​​​Amiodarone​

MEDICATIONS FOR RATE CONTROL
NICE: Offer a beta-blocker or a rate-limiting calcium-channel blocker (diltiazem [off-label use] or verapamil). The choice between a beta-blocker and a calcium-channel blocker will depend largely on the person's comorbidities. 

• Beta-blocker (works in 70% of patients):
  • metoprolol 2.5 - 5mg IV q20min up to 15mg, followed by 25-50mg PO
  • consider using if patient has HTN, CAD, diabetes, prior MI or hyperthyroidism
  • do NOT use in asthmatics or patients in acute heart failure
• Magnesium Sulfate
  • ​The LOMAGHI study (2018): A double-blind, randomized controlled trial. Intravenous MgSO4 appears to have a synergistic effect when combined with other AV nodal blockers resulting in improved rate control. Similar efficacy was observed with 4.5g and 9g of MgSO4 but a dose of 9 g was associated with more side effects.
  • Consider administering magnesium 2-4 g IV over 30 min as an adjunctive therapy
• Digoxin
  • is second line, as slow onset 
  • caution in renal failure
  • consider first line if hypotension or acute HF

IS TROPONIN NECESSARY FOR ALL ACUTE AF PATIENTS IN THE ED?

• In an unpublished review of charts at the University Health Network, 86% of patients had troponins drawn, 14% were positive and 5% of patients were treated as ACS – most of these had hypotension, signs of heart failure, or ECG changes after conversion or rate control
• Ischaemia may be the result or the cause of AF so consider doing troponins when there are clinical features of ACS present or risk factors for CAD.

AF WITH WIDE QRS

• Differential
  • AF with aberrancy (LBBB or RBBB)
  • AF with pre-excitation (WPW)
    • QRS morphology bizarre, polymorphic, much faster AF 
    • NEVER give AV nodal blocking agent (beta-blocker, calcium-channel blocker, adenosine, digoxin and even amiodarone)
    • Treatment: electrical cardioversion 

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​References

1. NICE CKS Atrial Fibrillation 
   
2. Canadian Cardiovascular Society Guidelines for management of AF 2018
3. European Society Cardiology Guidelines for management of AF 2016
4. ​CAEP Acute Atrial Fibrillation/Flutter Best Practices Checklist (2018)
5. https://emergencymedicinecases.com/episode-20-atrial-fibrillation/
6. http://www.stemlynsblog.org/should-we-rapidly-cardiovert-af-in-the-ed-st-emlyns/
7. https://www.aliem.com/2016/10/magnesium-for-rapid-atrial-fibrillation-rate-control/
8. https://www.aliem.com/2014/09/beta-blockers-vs-calcium-channel-blockers-atrial-fibrillation-rate-control-thinking-beyond-ed/

NBothma