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🫀 Atrial Fibrillation — Exam-Oriented Notes
Sources: Braunwald's Heart Disease, Fuster & Hurst's The Heart, Tintinalli's Emergency Medicine
1. DEFINITION
AF is a supraventricular arrhythmia characterized by:
- Disorganized atrial electrical activity (300–600 impulses/min)
- Irregularly irregular ventricular rhythm
- Absence of distinct P waves → replaced by fibrillatory (f) waves
Most common arrhythmia causing hospitalization (~33% of arrhythmia-related admissions). Associated with 5× ↑ stroke risk, 2× ↑ mortality, and 2× ↑ cognitive dysfunction.
2. ECG FEATURES — "3 I's of AF"
| Feature | Detail |
|---|
| Irregularly Irregular RR intervals | No consistent pattern |
| Isoelectric line absent | f waves (300–600/min), variable amplitude/shape |
| Invisible P waves | Replaced by f waves; best seen in V1, II |
Ventricular rate: 100–160 bpm (untreated)
- WPW + AF → rate can exceed 250 bpm via accessory pathway ⚠️ (dangerous — avoid AV nodal blockers)
- Very rapid rate (>170 bpm) → may falsely appear regular
3. CLASSIFICATION — "PP LP"
| Type | Definition |
|---|
| Paroxysmal | Self-terminates within 7 days (usually <48h) |
| Persistent | Lasts >7 days; requires intervention to terminate |
| Long-standing Persistent | Continuous AF >1 year |
| Permanent | Decision made not to restore sinus rhythm |
🧠 Mnemonic: "Paroxysmal Patients Linger Permanently"
Classification does not change based on effects of cardioversion or AAD therapy.
Autonomic subtypes (paroxysmal AF):
- Vagotonic AF (~25%): occurs at rest/sleep, worsened by digoxin → use disopyramide
- Adrenergic AF (~10–15%): during exertion → use beta-blockers
- Mixed/random (~60%): most common
4. CAUSES — Mnemonic "PIRATES"
| Letter | Cause |
|---|
| P | Pulmonary embolism / Pulmonary hypertension |
| I | Ischemic heart disease (CAD) |
| R | Rheumatic valvular disease (especially mitral stenosis) |
| A | Alcohol ("Holiday Heart"), Autonomic |
| T | Thyrotoxicosis (hyperthyroidism) |
| E | Electrolyte disturbance / Embolism |
| S | Sleep apnea / Structural heart disease (HCM, DCM, HF) |
Additional important causes:
- Hypertension (most common overall)
- Post-cardiac surgery (Post-op AF)
- Obesity, epicardial fat infiltration
- Amyloidosis, constrictive pericarditis
5. PATHOPHYSIOLOGY
Two key requirements:
- Trigger — most commonly from pulmonary vein ectopic foci (especially superior PVs)
- Substrate — atrial fibrosis, inflammation, dilatation → re-entrant circuits
Mechanisms:
- Multiple wavelet re-entry
- Rotors (stable high-frequency rotational sources)
- Atrial remodeling → fibrosis → reduced conduction velocity → perpetuation
Consequences:
- Loss of atrial kick → ↓ CO by 10–20% (worse in stiff LV/HFpEF)
- Tachycardia-induced cardiomyopathy (persistent rapid rate)
- LA thrombus → Left Atrial Appendage (LAA) is the site in 90% of cases → embolic stroke
6. CLINICAL FEATURES — Mnemonic "PFLS + Polyuria"
| Symptom | Note |
|---|
| Palpitations | Most common; may be absent in elderly |
| Fatigue | Often misattributed to aging |
| Lightheadedness | From ↓ CO |
| Shortness of breath / dyspnea | Especially on exertion |
| Polyuria | From atrial natriuretic peptide (ANP) release |
- 25% are asymptomatic (often elderly, persistent AF)
- Syncope: long pause on termination (sick sinus syndrome), or neurocardiogenic
- Can first present as stroke or heart failure
Exam Tip: AF + rapid irregular pulse + absent P waves on ECG = classic exam picture.
7. STROKE RISK — CHA₂DS₂-VASc Score
🧠 Mnemonic: "CHADs VASCULAR (2-1-1-1-2-1-1-1)"
| Letter | Risk Factor | Points |
|---|
| C | Congestive Heart Failure | 1 |
| H | Hypertension | 1 |
| A₂ | Age ≥75 years | 2 |
| D | Diabetes mellitus | 1 |
| S₂ | Stroke / TIA / thromboembolism (prior) | 2 |
| V | Vascular disease (MI, PAD, aortic plaque) | 1 |
| A | Age 65–74 years | 1 |
| Sc | Sex category (Female) | 1 |
Anticoagulation thresholds:
- Score 0 (men) or 1 (women): No anticoagulation
- Score 1 (men): Consider anticoagulation
- Score ≥2: Anticoagulate (Class I)
All patients ≥75 years automatically score ≥2 → anticoagulate regardless of AF type.
8. BLEEDING RISK — HAS-BLED Score
🧠 Mnemonic: "Has BLeD"
| Letter | Factor | Points |
|---|
| H | Hypertension (uncontrolled, SBP >160) | 1 |
| A | Abnormal renal/liver function | 1 each |
| S | Stroke history | 1 |
| B | Bleeding history or predisposition | 1 |
| L | Labile INR | 1 |
| E | Elderly (>65 years) | 1 |
| D | Drugs (antiplatelets/NSAIDs) or alcohol | 1 each |
Score ≥3 = high bleeding risk → does not contraindicate anticoagulation, but prompts caution and follow-up.
9. MANAGEMENT
A. Acute Management
Step 1 — Hemodynamically UNSTABLE:
→ Immediate DC cardioversion (synchronized)
Step 2 — Hemodynamically STABLE:
🧠 Mnemonic for acute AF: "ABCD"
- Anticoagulate
- Beta-blocker (rate control)
- Cardiovert (if indicated)
- Digoxin (adjunct, especially in HF)
Rate control targets:
- Rest: 60–80 bpm
- Moderate exercise: 90–115 bpm
| Drug | Use case |
|---|
| IV diltiazem / esmolol | First-line acute rate control |
| Beta-blockers | Rate control, adrenergic AF |
| Non-DHP CCBs (diltiazem, verapamil) | Rate control if no HF |
| Digoxin | HF with reduced EF, sedentary patients; poor at exercise rate control |
Cardioversion rules:
- AF <48 hours: Can cardiovert without prior anticoagulation (TEE optional)
- AF >48 hours or unknown duration: Anticoagulate ≥3 weeks before cardioversion, OR perform TEE to rule out LAA thrombus → then cardiovert
- Anticoagulate for ≥4 weeks after cardioversion regardless
B. Long-Term Management: Rate vs Rhythm Control
🧠 "Rate = AF accepted; Rhythm = restore sinus"
| Strategy | When to Choose |
|---|
| Rate control | Elderly, asymptomatic, permanent AF, large LA, failed cardioversions |
| Rhythm control | Young, symptomatic, HFrEF, first episode, short duration, small LA |
AFFIRM trial: Rate control = rhythm control in mortality outcomes (long-term).
C. Antiarrhythmic Drugs (Rhythm Control)
🧠 Mnemonic by structural heart disease:
| Situation | Drug |
|---|
| No structural heart disease | Flecainide, Propafenone ("pill-in-pocket") |
| HF/LV dysfunction | Amiodarone (drug of choice), Dofetilide |
| CAD | Sotalol, Amiodarone, Dofetilide |
| Hypertension with LVH | Amiodarone |
⚠️ Flecainide/propafenone are contraindicated in structural heart disease (pro-arrhythmic risk).
D. Anticoagulation
| Agent | Notes |
|---|
| DOACs (dabigatran, rivaroxaban, apixaban, edoxaban) | Preferred over warfarin in non-valvular AF — no INR monitoring, fewer drug interactions |
| Warfarin | INR target 2.0–3.0 (2.0–2.5 in elderly); still used in valvular AF (mitral stenosis, prosthetic valves) |
| WATCHMAN device | Percutaneous LAA closure — alternative when anticoagulation contraindicated |
⚠️ Valvular AF (rheumatic MS, prosthetic valves) = warfarin only, DOACs not recommended.
E. Non-Pharmacologic / Interventional
| Procedure | Indication |
|---|
| Catheter ablation (PV isolation) | Symptomatic paroxysmal/persistent AF refractory to AAD |
| AV node ablation + pacemaker | Rate control when drugs fail ("ablate and pace") |
| Surgical MAZE procedure | At time of open heart surgery |
| WATCHMAN device | LAA occlusion when anticoagulation contraindicated |
10. SPECIAL CLINICAL SITUATIONS
| Scenario | Key Point |
|---|
| WPW + AF | ⚠️ DO NOT give AV nodal blockers (digoxin, verapamil, diltiazem, beta-blockers) → may accelerate conduction via accessory pathway → VF. Use procainamide or cardioversion |
| AF + Mitral Stenosis | Warfarin regardless of CHA₂DS₂-VASc score; DOACs not effective |
| Post-operative AF | Common after cardiac surgery (peak 2–3 days post-op); beta-blockers prophylactically |
| Pregnancy + AF | Heparin (LMWH) preferred; warfarin teratogenic in 1st trimester; DOACs contraindicated |
| Thyrotoxicosis AF | Treat underlying hyperthyroidism; rate control with beta-blockers |
| HFrEF + AF | Rhythm control with amiodarone; ablation improves outcomes |
11. QUICK RECALL MNEMONICS — SUMMARY TABLE
| Mnemonic | What it covers |
|---|
| "3 I's" | ECG: Irregularly irregular, Isoelectric absent, Invisible P waves |
| "PP LP" | Classification: Paroxysmal, Persistent, Long-standing, Permanent |
| "PIRATES" | Causes of AF |
| "PFLS + Polyuria" | Symptoms |
| "CHADs VASc" | Stroke risk score |
| "Has BLeD" | Bleeding risk score |
| "ABCD" | Acute management: Anticoagulate, Beta-block, Cardiovert, Digoxin |
| "No SHD → Flec/Prop; HF → Amio" | Antiarrhythmic drug choice |
12. HIGH-YIELD EXAM FACTS
- Most common sustained arrhythmia in clinical practice
- Most common site of thrombus in AF = Left Atrial Appendage (LAA)
- Stoke risk = 5× higher in non-valvular AF
- WPW + AF → never give verapamil/digoxin/diltiazem/beta-blockers
- Valvular AF → warfarin, not DOACs
- Cardioversion after >48h AF → anticoagulate 3 weeks prior OR TEE to exclude thrombus
- Rate control targets: 60–80 bpm rest; 90–115 bpm exercise
- Digoxin: effective at rest but NOT during exercise for rate control
- Lone AF: historically = AF in patient <60y without hypertension or structural heart disease (term now abandoned)
- Holiday heart: AF triggered by acute alcohol intake (binge drinking)
- Polyuria in AF = due to ANP (atrial natriuretic peptide) release
- AFFIRM trial: no mortality difference between rate vs rhythm control strategies
— Braunwald's Heart Disease (10e); Fuster & Hurst's The Heart (15e); Tintinalli's Emergency Medicine