Internal MedicineCardiologyAtrial Fibrillation

Atrial Fibrillation

Must-Not-Miss / Red Flags

  • Rapid ventricular response >150 bpm with hypotension: urgent cardioversion
  • AF with WPW: delta waves + irregular wide‑complex tachycardia – avoid AV nodal blockers (risk of ventricular fibrillation)
  • Thrombus on TEE: absolute contraindication to cardioversion without anticoagulation
Patient Explanation
“Your heart’s upper chambers are beating irregularly instead of pumping smoothly. We’ll slow your heart rate, prevent clots, and discuss ways to restore a normal rhythm.”
Board Fact
“AF increases the risk of stroke 5‑fold; anticoagulation reduces this risk by 64%.”
ICD-10
I48.91

Definition & Core Concept

Atrial fibrillation (AF) is a supraventricular tachyarrhythmia characterized by uncoordinated atrial activation and ineffective atrial contraction, diagnosed by an irregularly irregular rhythm and absence of P waves on ECG.

Epidemiology & Risk Factors

  • Most common sustained arrhythmia; lifetime risk 1 in 4 after age 40
  • Prevalence increases with age: <1% at 80 years
  • Risk factors: hypertension, heart failure, valvular disease, obesity, sleep apnea, alcohol

Pathophysiology (Rule of 3)

  1. Triggers (ectopic foci in pulmonary veins) → rapid atrial firing
  2. Atrial substrate (fibrosis, dilation) → multiple reentrant circuits
  3. Atrial remodeling (electrical, structural) → “AF begets AF”

Clinical Presentation

  • Palpitations, fatigue, dyspnea, chest discomfort
  • Asymptomatic in up to 30% (detected on routine exam)
  • Irregularly irregular pulse, variable intensity of S1

Diagnostic Workup

ECG: absent P waves, irregularly irregular R‑R intervals, narrow QRS (unless aberrant). Echocardiogram: evaluate for valvular disease, LA size, LV function. Thyroid function: TSH (hyperthyroidism can trigger AF). Holter monitor: if paroxysmal suspected.

Management Protocol

  1. Rate control: Beta‑blocker (Metoprolol 25‑100 mg BID) or CCB (Diltiazem 120‑360 mg daily) – target resting HR <110 bpm
  2. Rhythm control: Flecainide or Amiodarone; catheter ablation if drug‑refractory
  3. Stroke prevention: CHA₂DS₂‑VASc ≥2 → anticoagulation (DOAC preferred); if CHA₂DS₂‑VASc = 1 → consider anticoagulation; 0 → no anticoagulation
  4. Cardioversion: if unstable, or elective if AF <48 hours (or TEE to rule out thrombus)

Complications & Prognosis

  • Thromboembolic stroke (5% annual risk without anticoagulation)
  • Tachycardia‑induced cardiomyopathy
  • Heart failure exacerbation

ICU Criteria

ICU admission if: rapid AF causing cardiogenic shock or acute pulmonary edema requiring urgent cardioversion.

Clinical Vignette

A 70‑year‑old man with hypertension presents with palpitations and fatigue. ECG shows AF with ventricular rate 130 bpm. Echo reveals mild LA enlargement, normal LV function. TSH is normal. CHA₂DS₂‑VASc = 3 (age, HTN, vascular disease).

Pearls & Pitfalls

  • Rate control is non‑inferior to rhythm control for most patients; rhythm control is preferred in younger, symptomatic patients or those with AF‑related cardiomyopathy.
  • Anticoagulation should not be interrupted for cardioversion if AF duration >48 hours or unknown.

Discharge & Follow-Up

Monthly INR checks if on Warfarin (no monitoring with DOACs). Annual echocardiogram. Lifestyle modifications: weight loss, alcohol reduction, sleep apnea treatment.

Literature & Guidelines

ACC/AHA/ACCP/HRS 2024 Guideline for AF Management. PMID: 38538109.

Personal Clinical Notes