Atrial Fibrillation

Rapid, irregular contractions of the atria (“quivering”) with variable ventricular rate. The rhythm itself is harmless, but it is prone to causing a reduced left-ventricular end-diastolic volume (LVEDV), which can lead to a reduced cardiac output at elevated heart rates. Along with this, the incongruent contractions of the atrial walls may lead to stasis of blood within these chambers, allowing for formation of an intracardiac thrombus (most often within the left atrial appendage).

Notice how there are no p-waves, but there are “fibrillatory” waves between QRS complexes. The rhythm is also irregularly-irregular.

4 Categories

• Paroxysmal: Occasional episodes that terminate spontaneously (or therapeutically) in <7 days
• Persistent: Episodes that last >7 days
• Long-term persistent: Episodes that last >12 months
• Permanent: When atrial fibrillation is accepted by both patient and provider and no further attempts at conversion to sinus rhythm will be made

Causes

• Heart Failure
• Valvular heart disease
• Hyperthyroidism
• Pulmonary Embolism
• Obstructive Sleep Apnea
• Acute Coronary Syndrome
• Infection
• Pain
• Dehydration
• Hypertension
• Electrolyte derangements (hypokalemia, hypomagnesemia)

Management

• First step is always A, B, Cs (Airway, breathing, circulation)
  • If hemodynamically unstable, synchronized cardioversion is necessary
  • If hemodynamically stable with HR > 100 bpm (rapid ventricular response), goal is to keep heart rate < 110 bpm ₍₁₎
    • Achievable through use of PO or IV Metoprolol, or commonly a continuous titratable diltiazem infusion may be used. Of course, the blood pressure needs to be able to tolerate these anti-hypertensive medications, though the blood pressure may actually increase with the use of AV-node blocking agents as the slowed heart rate allows for a larger end-diastolic volume (EDV) and, therefore, an increase in cardiac output

• Acute (new-onset and certain that it has persisted <48 hours)
  • Cardioversion
    • Electrically (synchronized cardioversion)
    • Pharmacologically (Flecainide, Amiodarone, sotalol, etc.)
  • Anticoagulate for 3-4 weeks after
• Chronic (rhythm has persisted over 48 hours or it is unclear how long the episode has lasted)
  • Anticoagulate for 3-4 weeks
  • TEE to assess for thrombus in left atrial appendage
  • Cardiovert (either electrically or pharmacologically as above)
    • Other options include AV node ablation with pacemaker insertion or atrial fibrillation ablation (usually at the pulmonary veins, where atrial fibrillation most commonly originates from)
  • Anticoagulate for 3-4 more weeks (or indefinitely based on CHA₂DS₂VASc score)
    • CHF = 1 point
    • Hypertension = 1 point
    • Age; 65-74 = 1 point, 75+ = 2 points
    • Diabetes = 1 point
    • Stroke history = 2 points
    • Vascular disease = 1 point
    • Sex Category (female) = 1 point
    • 2+ is an indication for long-term anticoagulation (though this risk should be weighed against the risk of bleeding, calculated with a HAS-BLED score)
    • Alternative to anticoagulation may include placement of left atrial appendage closure device
• Long-term management of paroxysmal atrial fibrillation or atrial fibrillation that is refractory to conversion to normal sinus rhythm
  • Rate-Control (Beta Blockers, calcium channel blockers, digoxin) vs Rhythm-Control (Amiodarone)
    • No difference in mortality (AFFIRM Trial ₍₂₎)
  • Anticoagulation
    • Using CHA₂DS₂VASc score as above
    • Valvular Atrial Fibrillation: Warfarin (DOACs have not had a sufficient amount of evidence to be used at this time)
    • Non-Valvular Atrial Fibrillation: DOACs may be used (Apixaban, dabigatran, rivaroxaban, etc.)

References

1. Gelder, I. C., Groenveld, H. F., Crijns, H. J., Tuininga, Y. S., Tijssen, J. G., Alings, A. M., . . . Berg, M. P. (2010). Lenient versus Strict Rate Control in Patients with Atrial Fibrillation. New England Journal of Medicine, 362(15), 1363-1373. doi:10.1056/nejmoa1001337
2. A Comparison of Rate Control and Rhythm Control in Patients with Atrial Fibrillation. (2002). New England Journal of Medicine, 347(23), 1825-1833. doi:10.1056/nejmoa021328