EP Staff Education Clinical Staff Ilyas Colombowala, MD, FACC, FHRS →
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Condition

Atrial Fibrillation

Disorganized atrial activation, most commonly driven by triggers from the pulmonary vein sleeves. Spectrum from paroxysmal to long-standing persistent, with progressive atrial remodeling over time.

ECG features

  • ▸Irregularly irregular RR intervals without a repeating pattern
  • ▸No discrete P waves; fibrillatory baseline (coarse or fine) between QRS complexes
  • ▸Ventricular rate typically 90–170 bpm in untreated AF, slower in patients on AV-nodal blockers
  • ▸Narrow QRS unless pre-existing bundle branch block or rate-related aberrancy
  • ▸Ashman phenomenon: aberrantly conducted beats following a long-short cycle
  • ▸Apparent regularity at slow rates raises suspicion for complete AV block with junctional escape

Differential

  • ▸Atrial flutter with variable AV conduction (look for sawtooth in II/III/aVF)
  • ▸Multifocal atrial tachycardia (≥3 P-wave morphologies, discrete Ps still visible)
  • ▸Frequent PACs producing an irregular rhythm but with identifiable sinus Ps
  • ▸Sinus arrhythmia (gradual rate variation tied to respiration)
  • ▸Atrial tachycardia with Wenckebach conduction

Mechanism

AF is the end result of two interacting forces: triggers that initiate the arrhythmia and substrate that sustains it.

  • Triggers: ectopic firing from myocardial sleeves extending into the pulmonary veins accounts for the majority of paroxysmal initiations. Non-PV triggers — superior vena cava, coronary sinus, ligament of Marshall, left atrial appendage, crista terminalis — become more relevant in persistent disease and after a failed first ablation.
  • Substrate: atrial stretch, fibrosis, inflammation, and autonomic remodeling shorten refractoriness and create regions of slow, anisotropic conduction. Rotors and multiple wavelets propagate through this tissue.
  • Remodeling is bidirectional: AF begets AF. Each episode shortens atrial refractoriness within hours and promotes fibrosis over months. This is why early intervention matters.

Classification by burden

  • Paroxysmal: self-terminates within 7 days (usually within 24 h)
  • Persistent: sustained beyond 7 days or requires cardioversion
  • Long-standing persistent: continuous AF more than 12 months
  • Permanent: a shared decision to abandon rhythm control, not a mechanistic category

ECG features

The hallmark is irregular irregularity without organized atrial activity. Look at lead V1 for the cleanest view of fibrillatory waves; coarse f-waves can mimic flutter but lack the consistent sawtooth and cycle length. Watch for hidden flutter in patients on antiarrhythmics — class IC drugs in particular can organize AF into a slow, 1:1-conducting atypical flutter.

A regularized AF rhythm in a previously irregular patient should prompt one of three thoughts:

  • Complete heart block with junctional or ventricular escape
  • Conversion to atrial tachycardia or flutter
  • Ventricular paced rhythm

Work-up

  • 12-lead ECG to confirm and exclude pre-excitation
  • TTE for chamber sizes, LV function, valvular disease, pericardial effusion
  • Labs: TSH, CBC, BMP, magnesium
  • Ambulatory monitoring when paroxysmal and capture is needed: patch monitor for symptom correlation, longer monitors or implantable loop recorders for cryptogenic stroke work-up
  • Sleep evaluation — OSA is massively under-diagnosed in our AF population and a top driver of recurrence
  • TEE or cardiac CT for pre-ablation planning and LAA thrombus exclusion

Treatment overview

  • Rate control: beta-blockers, non-DHP calcium channel blockers, digoxin in selected patients. RACE II target is a resting rate under 110 if asymptomatic.
  • Rhythm control: cardioversion, antiarrhythmics (flecainide and propafenone in structurally normal hearts; sotalol, dofetilide, amiodarone otherwise), and catheter ablation.
  • Anticoagulation: DOAC preferred over warfarin in non-valvular AF. CHA2DS2-VASc ≥2 in men or ≥3 in women drives treatment. LAA occlusion for patients with absolute or relative contraindications to long-term anticoagulation.
  • Risk factor modification: weight loss, OSA treatment, BP control, alcohol reduction, exercise. The LEGACY data are persuasive — patients who lose >10% body weight have markedly better ablation outcomes.

What we do in clinic

For a new AF referral, the first visit covers:

  • Confirming the arrhythmia and characterizing the burden
  • Stroke risk stratification and anticoagulation decision
  • Symptom assessment — many “asymptomatic” patients describe substantial fatigue once asked specifically
  • A frank conversation about early rhythm control. We favor ablation early in symptomatic paroxysmal AF; EAST-AFNET 4 and CABANA subgroup data support this.
  • Setting up a sleep study if there’s any clinical suspicion

Repeat ablations are common (15–25% at 1–2 years) and usually reveal PV reconnection or new non-PV triggers. We counsel patients up front so a touch-up isn’t framed as failure.

Watch

Short videos to help illustrate this topic. Embedded from the original channels — content belongs to them.

Video pending Add a youtube video ID to display: Pulmonary vein triggers and AF initiation
Pulmonary vein triggers and AF initiation · EP educational channel · Short animation on PV sleeve myocardium and trigger physiology.

Last reviewed by Dr. Colombowala on May 22, 2026.

Not medical advice. This page is educational. Your situation may differ — discuss it with Dr. Colombowala or your treating physician before making decisions.