Atrial Fibrillation
Chaotic re-entrant electrical activity replaces organised atrial contraction, so the atria quiver rather than pump, producing an irregularly irregular pulse and blood stasis that drives thromboembolic risk independent of how the rhythm is managed.
In a nutshell
Chaotic re-entrant wavelets replace organised atrial contraction, producing an irregularly irregular pulse and stasis in the fibrillating atria. Stroke risk comes from that stasis, not from symptoms, so anticoagulation is decided by CHA2DS2-VASc independently of whether rate or rhythm control is chosen.
Classic presentation
An older patient with palpitations or incidental irregular pulse on routine examination, confirmed by an ECG showing no P waves and an irregularly irregular rhythm.
Key points
- The irregularly irregular pulse and absent P waves both come directly from disorganised atrial electrical activity replacing a single coordinated wavefront.
- Loss of the atrial kick matters most in stiff ventricles (LVH, aortic stenosis, HFpEF), where it can precipitate acute decompensation.
- Stroke risk is generated by stasis in the fibrillating atria (especially the left atrial appendage), so anticoagulation is decided by CHA2DS2-VASc regardless of the chosen rhythm strategy.
- Rate control (beta-blocker or rate-limiting calcium channel blocker) is first-line unless rhythm control is specifically indicated.
- Haemodynamic instability from AF is an indication for emergency electrical cardioversion, not stepwise drug therapy.
First-line investigation
12-lead ECG: it directly shows the absent P waves and irregularly irregular rhythm that define the mechanism and confirm the diagnosis.
First-line management
Assess for instability; if stable, start rate control and calculate CHA2DS2-VASc to decide on anticoagulation, independent of rate versus rhythm strategy.
Exam traps
- Anticoagulation is not decided by how symptomatic the AF is; it is decided by CHA2DS2-VASc, because stroke risk comes from stasis, not symptoms.
- New AF with adverse haemodynamic features needs emergency cardioversion, not a beta-blocker trial first.
- Cardioversion in AF present for over 48 hours (or of uncertain duration) carries its own thromboembolic risk and needs anticoagulation or a transoesophageal echocardiogram first.
- A regular pulse does not exclude a prior AF diagnosis; flutter or successful rate/rhythm control can regularise the rhythm.
Educational content pending clinical review. Not medical advice.