Atrial Fibrillation

• Goals:
  • Identify and treat underlying structural heart disease and other predisposing conditions
  • Relieve symptoms
  • Improve functional capacity/quality of life
  • Reduce morbidity/mortality associated with AF/AFL
  • Prevent tachycardia-induced cardiomyopathy
  • Reduce/prevent emergency room visits or hospitalizations secondary to AF/AFL
  • Prevent stroke or systemic thromboembolism 
• How do you decide if you are going to pursue rate or rhythm control for a patient with AF

• No right or wrong answer
• Often, the two are simultaneous:
• Rhythm control requires good rate control when patient goes back into AF

• Bottom line:
  • Asymptomatic patients can be managed with rate control. (no benefit in rhythm control).
  • Resting HR <110bpm as long as LVEF > 40%.

Rhythm Control

• Recommended in patients in who remain symptomatic with rate control therapy or in whom rate control therapy is unlikely to control symptoms.
• Two Types:
  • Continuous.
  • Intermittent ("pill in pocket")

    • CCS Guideline: We recommend intermittent antiarrhythmic drug therapy ("pill in pocket") in symptomatic patients with infrequent, longer-lasting episodes of AF/AFL as an alternative to daily antiarrhythmic therapy. (Strong Recommendation, Moderate Quality )     

    • Single dose flecainide (200-300 mg) or propafenone (450-600 mg) as an oral dose
    • Often prescribed with a short-acting beta-blocker at the same time (metoprolol 50-100 mg) to take 30min before antiarrhythmic or be on background rate control
      • ...due to concern of post-conversion pause.  
      • First time antiarrhythmic conversion should be monitored to ensure no post-conversion pause.
    • (As long as no sinus/AV dysfunction, no bundle block, no long QT)
• ​Agents: (From Skanes et al 2012, Can. J. Cardiol.)

  • Drug/Dose	Efficacy	Toxicity	Comments
    Flecainide 50-150mg BID	30-50%	- Ventricular tachycardia - Bradycardia - Rapid vetricular response to   AF/Flutter (1:1 conduction)	- CONTRAINDICATED IN:          CAD and LV dysfunction - Should combine with AV   nodal blocking agent.
    Propafenone 150-300mg TID	30-50%	- Ventricular tachycardia    or bradycardia - Rapid ventricular response   to AF/Flutter (1:1 conduction) - Abnormal taste	- CONTRAINDICATED IN:          CAD and LV dysfunction - Should combine with AV   nodal blocking agent.
    Amiodarone 100-200mg OD (After 10g loading)	60-70%	- Photosensitivity - Bradycardia - GI upset - Thyroid dysfunction - Hepatic toxicity - Neuropathy - Tremor - Pulmonary Toxicity (fibrosis) - Torsades de Pointes (rare)	- Low risk of pro-arrhythmia - Limited by side effects. - Side Effects are dose and duration   dependent.
    NEW!! (limited  experience)   Dronedarone 400mg BID	40%	- GI upset - Bradycardia - Hepatic Toxicity	- CONTRAINDICATED IN:    CHF and LVEF < 40% - Caution when added to digoxin - Liver enzyme monitoring required
    Sotalol 80-160mg BID	30-50%	- Torsades de pointes - Bradycardia - B-blocker side effects	- AVOID in pts with high risk of Torsades   (esp Female, >65, on diuretics, with renal   disease) - Monitor QT interval 1w after starting - Caution when EF < 40%

• NOTE: Rhythm control DOES NOT replace anticoagulation. (no evidence reduces risk of thromboembolism)
  • Should still receive anticoagulation for thromboembolic prophylaxis (CCS guidelines)
• Amiodarone (Class III antiarrhythmic)
• Dronedarone (Class III antiarrhythmic)
  • Newer agent to amiodarone (approved for paroxysmal afib).
  • Less end-orgen side-effects of amiodarone
    • (i.e. less thyroid, liver, and pulmonary function)
  • CCS Guidelines 2014:
    • Dronedarone is a good choice for RHYTHM control in selected AF pts with nonpermanent (predonimantly paroxysmal AF) with minimal structural heart disease.
    • Consider monitoring for LFTs within 6mo of initiating therapy.
  • NOTE: Raises creatinine (partial inhibition of tubular transport of creatinine --> elevated serum levels), but does not affect GFR (regard new creat as a new baseline - i.e. CrCl drops, GFR unchanged)
    • Metabolized by liver, does not need renal dosing.
  • DO NOT USE in:
    • Severe heart failure
      • Recent hospitalization for HF shown to have 2-fold increase in mortality with dronedarone.
    • Permanent atrial fibrillation (higher rates of hospitalization for HF, stroke, death from CV causes)
    • CCS Guidelines: (based on ANDROMEDA Trial)
      • DO NOT use in LVEF < 40%
      • DO NOT use for only rate control
      • CAUTION when taking digoxin
• Electrical Cardioversion:
  • If unstable (see ACLS flow charts)
  • If rhythm control strategy chosen, and patient flips back after non-pre-treated electrical cardioversion, then pre-treat with antiarrhythmics prior to doing a cardioversion.
  • 150-200J biphasic waveform recommended as initial energy setting.
• RF Ablation
  • 9 RCTs / 3 systematic reviews in 1274 patients who have failed ≥ 1 drug
  • uniformly demonstrate large differences in recurrence of AF
    • (OR 9.74 95% CI, 3.98 to 23.87) in favourof ablation vsAAD 
  • Quite low risk, largest risk:
    • Tamponade 1.31% rate (worldwide study)
    • TIA 0.71% rate
    • Femoral pseudoaneurism 0.93% rate
    • AV Fistula 0.54
    • TOTAL Risk of complications: 4.54%.
  • CCS Guideline:
    • We recommend catheter ablation of AF in patients who remain symptomatic

      following adequate trials of anti-arrhythmic drug therapy and in whom a rhythm

      control strategy remains desired. 

• We recommend curative catheter ablation for symptomatic patients with typical atrial flutter as first line therapy or as a reasonable alternative to pharmacologic rhythm or  rate control therapy. 

Ablation

• Typically if symptomatic and treated at least with one antiarrhythmic agent unsuccessfully.
• Pulmonary veins ablation
  • Entails electrical isolation of pulmonary veins, so premature complexes that originate in pulmonary veins cannot initiate fibrillation.
    • In the past: complication of pulmonary vein stenosis, but now can perform without this risk (do not enter ostia of pulmonary veins).
  • Must stay on warfarin for 2-3mo post-ablation, then anticoagulation is based on CHADS2 score.
  • Success rate 84% AFib free at 1 year, often needs to be repeated.
  • Complications (4.5% of patients)
    • Stroke
    • Atrial-esophageal fistula
    • Pulmonary veins tenosis
    • Cardiac tamponade
    • Death.
• 2nd Line: AV node ablation
  • Pacemaker inserted at time of ablation to control ventricular rate.
  • Small risk of polymorphic VT. (reduce by increase paced heart rate by 2mo after procedure).
• MAZE Surgery
  • Several incisions or ablations in R or L atria which interrupt re-entrant pathways required for afib maintenance.
  • Not studied head-to-head with pulmonary vein isolation, but success rate long-term is similar.