Atrial Fibrillation

Risk factors

• Hypertension (most common identifiable cause)
• Coronary artery disease, valvular disease (especially mitral)
• Hyperthyroidism — always check TSH on new diagnosis
• Obesity, obstructive sleep apnea
• Alcohol use ('holiday heart'), stimulants
• Diabetes, CKD
• Pericarditis, recent cardiac surgery

Pathophysiology

Ectopic foci, typically arising from the pulmonary vein ostia, trigger multiple re-entrant wavelets in remodeled atrial tissue. Loss of organized atrial contraction reduces cardiac output by ~20% (loss of atrial kick) and promotes thrombus formation in the left atrial appendage — the substrate for embolic stroke.

Clinical presentation

Differential diagnosis

• Atrial flutter with variable AV block — Sawtooth flutter waves (II, III, aVF) identify; can mimic AFib's irregularity when conduction ratio varies
• Multifocal atrial tachycardia (MAT) — ≥3 distinct P-wave morphologies in same lead; typically COPD or hypoxic patient; treat underlying cause + non-DHP CCB
• Atrial tachycardia with variable AV block — Single ectopic P-wave morphology (different from sinus); variable AV conduction creates irregularity
• Frequent premature atrial contractions (PACs) — Irregular rhythm but discrete P waves visible (often abnormal morphology); usually benign in structurally normal hearts
• Ventricular bigeminy or trigeminy — Wide-complex pattern with regular sequence; PVC after each (or every other) sinus beat
• Sinus arrhythmia — Phasic variation with respiration in young/healthy patients; P-wave morphology preserved
• Wandering atrial pacemaker — ≥3 P-wave morphologies but rate <100 (vs MAT >100); usually benign

Diagnostic workup

Diagnostic algorithm

flowchart TD
  A[New AFib<br/>diagnosis] --> B[Calculate<br/>CHA2DS2-VASc]
  B --> C{Score}
  C -->|Men ≥2<br/>Women ≥3| D[Anticoagulate]
  C -->|Men 0-1<br/>Women 0-2| E[Reassess<br/>periodically]
  D --> F{Valvular AFib?<br/>mech valve / mod-sev MS}
  F -->|Yes| G[Warfarin<br/>INR 2-3]
  F -->|No| H[DOAC preferred<br/>apixaban / rivaroxaban / edox / dabig]
  A --> I[Rate vs Rhythm<br/>strategy]
  I --> J[Rate Control<br/>BB or non-DHP CCB]
  I --> K[Rhythm Control<br/>cardiovert + AAD<br/>or PVI ablation]

Treatment

Complications

• Embolic stroke (5× increased risk; ~15% of all ischemic strokes are AFib-related)
• Tachycardia-induced cardiomyopathy from chronic rapid ventricular response
• Heart failure decompensation
• Anticoagulation-related bleeding

PANCE pearls

• CHA2DS2-VASc: CHF (1), HTN (1), Age ≥75 (2), Diabetes (1), Stroke/TIA history (2), Vascular disease (1), Age 65-74 (1), Sex (female) (1). Score ≥2 men or ≥3 women → anticoagulate.
• HAS-BLED estimates bleeding risk but does NOT exclude patients from anticoagulation — it identifies modifiable bleeding risk factors.
• Cardioversion safety: <48 h from onset → cardiovert without prior AC. >48 h or unknown → either TEE-guided or 3 weeks AC first. Always anticoagulate ≥4 weeks after cardioversion regardless.
• Wolf-Parkinson-White + AFib: AVOID AV-nodal blockers (BB, CCB, digoxin, adenosine) — can precipitate VF. Use procainamide or cardiovert.
• Holiday heart syndrome: AFib triggered by acute alcohol binge; usually self-terminates with abstinence and supportive care.

Images

References

• ACC/AHA/ACCP/HRS 2023 — 2023 ACC/AHA/ACCP/HRS Guideline for the Diagnosis and Management of Atrial Fibrillation (Joglar et al., Circulation 2024)
• EAST-AFNET 4 — Early Rhythm-Control Therapy in Patients with Atrial Fibrillation (Kirchhof et al., NEJM 2020)
• AFFIRM — A Comparison of Rate Control and Rhythm Control in AFib (Wyse et al., NEJM 2002)
• CHA2DS2-VASc — Refining Clinical Risk Stratification for Stroke in AFib (Lip et al., Chest 2010)
• RE-LY / ARISTOTLE / ROCKET-AF — DOAC pivotal trials vs warfarin in AFib (Connolly NEJM 2009; Granger NEJM 2011; Patel NEJM 2011)