---

Atrial Fibrillation (AF)

Definition & ECG Features

• Low-amplitude baseline oscillations (fibrillatory / f-waves) from chaotically firing atria at 300–600 beats/min, variable in amplitude, shape, and timing
• Irregularly irregular ventricular rhythm — the hallmark clinical sign
• Absent discrete P waves
• Ventricular rate during untreated AF is typically 100–160 beats/min

---

Classification

---

Epidemiology

• Affects ~12% of adults ≥75 years and 18% of those ≥85 years
• About one-third of all AF patients are ≥80 years (2019 AHA/ACC/HRS guideline estimate)
• Common comorbidities: hypertension, coronary heart disease, obesity, sleep apnea, hyperlipidemia, heart failure

---

Mechanisms

1. Trigger: Ectopic impulses, often from the pulmonary veins, initiate AF
2. Substrate: Atrial fibrosis, conduction abnormalities, and stretch provide a favorable re-entrant environment
3. Remodeling: AF itself causes electrical and structural remodeling ("AF begets AF") — progressive shortening of the atrial refractory period and loss of rate adaptation
4. Autonomic influences: Vagal or adrenergic tone can both precipitate and maintain AF depending on the subtype

---

Causes / Risk Factors

• Hypertension (most common)
• Ischemic / structural heart disease
• Valvular disease (especially mitral stenosis — MS + AF carries near-prosthetic-valve stroke risk; warfarin, not DOACs, required in rheumatic MS)
• Thyrotoxicosis
• Heart failure (both cause and consequence)
• Obesity, sleep apnea
• Alcohol ("holiday heart")
• Post-cardiac surgery
• Genetic factors (familial AF, mutations in ion channel and gap junction genes)

---

Clinical Features

• Palpitations, fatigue, reduced exercise tolerance
• Dyspnea, lightheadedness, chest discomfort
• Acute pulmonary edema (loss of atrial kick in a stiff LV)
• Syncope, fall, or stroke as initial presentation (especially in elderly)
• Frequently asymptomatic — subclinical AF detected on implanted devices in up to 50% of pacemaker/ICD patients

• Stroke / thromboembolism: Nonvalvular AF → 5-fold increase in stroke risk; strokes tend to be severe
• Heart failure (rate-related cardiomyopathy)
• Cognitive impairment, reduced physical performance, increased mortality

---

Diagnostic Evaluation

• ECG — gold standard; 12-lead or rhythm strip
• Holter / event monitor — for paroxysmal AF
• Implantable loop recorder — high yield for cryptogenic stroke workup
• Echocardiography — assess structural disease, LA size, LV function, thrombus (especially transesophageal echo before cardioversion)
• TFTs, CMP, CBC — exclude reversible causes
• CHA₂DS₂-VASc score — stroke risk stratification
• HAS-BLED score — bleeding risk assessment

---

Stroke Prevention (Anticoagulation)

CHA₂DS₂-VASc Score

• Men with CHA₂DS₂-VASc ≥ 2 → anticoagulate
• Women with CHA₂DS₂-VASc ≥ 3 → anticoagulate
• All patients ≥75 years (score ≥ 2 by definition) → anticoagulate regardless of AF type

• DOACs (dabigatran, rivaroxaban, apixaban, edoxaban) preferred over warfarin for nonvalvular AF — no dietary restrictions, no INR monitoring, similar or better efficacy with less bleeding in elderly
• Warfarin (target INR 2–3) remains first choice in rheumatic mitral stenosis and mechanical valves (DOACs are contraindicated in these)
• Aspirin is NOT effective for stroke prevention in AF; no longer recommended for this purpose
• In elderly, typical warfarin maintenance dose is 2–5 mg/day, often started without a loading dose

---

Acute Management

Hemodynamically Unstable AF

• Immediate direct-current cardioversion (DCCV) — biphasic shock, typically starting at 200 J

Hemodynamically Stable AF

• IV β-blocker (metoprolol, esmolol) or non-dihydropyridine CCB (diltiazem, verapamil)
• Digoxin — slower onset, useful in HF with reduced EF
• Amiodarone — when other agents fail or in hemodynamically compromised patients

• If AF onset ≤48 hours, cardioversion can proceed after anticoagulation with heparin
• If AF onset >48 hours or unknown duration: anticoagulate for ≥3 weeks before cardioversion OR perform transesophageal echo (TEE) to rule out LA thrombus, then cardiovert with adequate anticoagulation
• Anticoagulation must continue for ≥4 weeks after successful cardioversion regardless of CHA₂DS₂-VASc score (due to atrial stunning)

---

Long-Term Management: Rate vs. Rhythm Control

• Symptomatic patients despite rate control
• First-episode or young patients
• AF contributing to HF or tachycardia-induced cardiomyopathy

---

Antiarrhythmic Drug (AAD) Selection

---

Nonpharmacologic Management

Catheter Ablation (Pulmonary Vein Isolation, PVI)

• First-line rhythm control option in symptomatic paroxysmal AF refractory to or intolerant of AADs (Class I)
• Superior to AADs for maintaining sinus rhythm in paroxysmal AF
• Growing evidence supports early ablation, even as first-line, in selected patients
• In HF with reduced EF + AF, ablation significantly reduces mortality and hospitalization vs. rate control (CASTLE-AF trial)

Left Atrial Appendage (LAA) Occlusion

• Watchman device (percutaneous LAA closure) — for patients with nonvalvular AF who have contraindications to long-term anticoagulation
• Surgical LAA excision/ligation during concomitant cardiac surgery

Upstream Risk Factor Modification

• Weight loss, treatment of sleep apnea, blood pressure control, and exercise can reduce AF burden
• Addresses the AF substrate directly

---

Special Situations

---