Cardiovascular · Topic 15 of 48
Atrial Fibrillation
Cardiovascular · arrhythmia
Atrial Fibrillation
An irregularly irregular rhythm: shock it if unstable, otherwise control the rate, and anticoagulate by stroke risk — not by the rhythm you restore.
Key numbers
Rate control: beta-blocker or diltiazemrest HR < 100–110
Anticoagulate at CHA₂DS₂-VASc ≥2 men, ≥3 womenscore ≥ 2 men, ≥ 3 women
AF ≥48 h: 3 weeks anticoagulation or TEE≥ 48 h: 3 wk before
01 · GiveRate control: beta-blocker or diltiazem
For stable rapid AF give a beta-blocker (metoprolol, esmolol) or diltiazem/verapamil (only if LVEF > 40%); aim for a resting rate under 100–110 bpm, guided by symptoms.
02 · The ruleAnticoagulate at CHA₂DS₂-VASc ≥2 men, ≥3 women
Anticoagulate when annual stroke risk is ≥ 2% (CHA₂DS₂-VASc ≥ 2 in men, ≥ 3 in women); it is reasonable at 1 (men) or 2 (women). Aspirin, alone or with clopidogrel, is not a substitute.
03 · DoUnstable AF: immediate synchronized cardioversion
If AF causes hemodynamic instability (hypotension, shock, ischemia, acute heart failure), perform immediate synchronized electrical cardioversion; the 2025 AHA initial energy is at least 200 J biphasic, escalating if it fails.
01
Diagnosis & monitoring
Work-upIrregularly irregular, no P waves must knowAF on ECG: no P waves, irregular fibrillatory baseline waves (atrial rate over 300/min, best seen in V1) and irregularly irregular R-R intervals, usually with a narrow QRS.
CHA₂DS₂-VASc: 2 points for age ≥ 75, strokeCHA₂DS₂-VASc: CHF 1, hypertension 1, age ≥ 75 = 2, diabetes 1, prior stroke/TIA/thromboembolism 2, vascular disease 1, age 65–74 = 1, female sex 1.
Ibutilide: monitor ECG 4 hours for torsadesIbutilide converts AF quickly but prolongs QT and can cause torsades de pointes; monitor the ECG continuously during and for 4 hours after the infusion, and avoid it with low LVEF or a long QT.
02
Do right now
In this orderFirst moves
1
→Unstable AF: immediate synchronized cardioversion
2
→Wide irregular AF with WPW: no AV-nodal blockers
3
→Rate control: beta-blocker or diltiazemrest HR < 100–110
4
Anticoagulate at CHA₂DS₂-VASc ≥2 men, ≥3 womenscore ≥ 2 men, ≥ 3 women
Why each step
Unstable AF: immediate synchronized cardioversionIf AF causes hemodynamic instability (hypotension, shock, ischemia, acute heart failure), perform immediate synchronized electrical cardioversion; the 2025 AHA initial energy is at least 200 J biphasic, escalating if it fails.
Wide irregular AF with WPW: no AV-nodal blockersPreexcited AF (WPW: fast, irregular, wide and varying QRS) must not get AV-nodal blockers (adenosine, beta-blockers, diltiazem, verapamil, digoxin, amiodarone) — they can precipitate VF. Cardiovert if unstable; give IV procainamide or ibutilide if stable.
Rate control: beta-blocker or diltiazemFor stable rapid AF give a beta-blocker (metoprolol, esmolol) or diltiazem/verapamil (only if LVEF > 40%); aim for a resting rate under 100–110 bpm, guided by symptoms.
Anticoagulate at CHA₂DS₂-VASc ≥2 men, ≥3 womenAnticoagulate when annual stroke risk is ≥ 2% (CHA₂DS₂-VASc ≥ 2 in men, ≥ 3 in women); it is reasonable at 1 (men) or 2 (women). Aspirin, alone or with clopidogrel, is not a substitute.
03
Management
OrdersDOAC first; warfarin for mechanical valve, rheumatic MSPrefer a DOAC (apixaban, rivaroxaban, edoxaban, dabigatran) over warfarin; use warfarin (INR 2.0–3.0) for AF with a mechanical heart valve or moderate-to-severe rheumatic mitral stenosis.
Digoxin is second-line, mainly in heart failureDigoxin is the least effective rate-control drug (it fails during exertion) but is useful as an add-on or in heart failure; when levels are measured, target a serum digoxin level below 1.2 ng/mL.
Order echocardiogram and thyroid testsEvaluate new AF with an ECG, transthoracic echo and thyroid function tests, and look for triggers: hypertension, CAD, valve disease, hyperthyroidism, binge alcohol, pulmonary embolism, sleep apnea, pericarditis.
Early rhythm control; ablation first-line in selected patientsCurrent guidance favors early rhythm control to reduce AF burden: catheter ablation (pulmonary vein isolation) is class 1 after antiarrhythmic failure, in HFrEF, and first-line in selected patients.
04
Red flags & don'ts
Avoid harmNo diltiazem or verapamil if LVEF < 40% avoidDo not give nondihydropyridine CCBs to patients with AF and LVEF < 40% or decompensated heart failure — they worsen HF. Use a beta-blocker cautiously, digoxin, or IV amiodarone in the critically ill.
No class IC drugs after MI or HFrEF avoidClass IC agents (flecainide, propafenone) raise mortality after MI and in significant structural heart disease or HFrEF; amiodarone is the most effective antiarrhythmic and is used when structural disease is present.
05
The rules
Know theseAF ≥48 h: 3 weeks anticoagulation or TEE must knowBefore elective cardioversion of AF lasting ≥ 48 hours, give 3 weeks of uninterrupted therapeutic anticoagulation or exclude left atrial thrombus by TEE; continue anticoagulation at least 4 weeks afterwards.
Restoring sinus rhythm does not stop anticoagulationLong-term anticoagulation follows stroke risk, not rhythm: continue it after cardioversion or a seemingly successful ablation in any patient who meets the CHA₂DS₂-VASc threshold.
HAS-BLED flags fixable bleeding risks, not refusalBleeding scores (HAS-BLED) should not be used alone to withhold anticoagulation; use them to correct modifiable risks such as uncontrolled hypertension, NSAID or antiplatelet use, alcohol and labile INR.
06
More detail
ReferenceShow 7 reference facts
Paroxysmal AF ends within 7 days; persistent AF lasts more than 7 days; long-standing persistent more than 12 months; permanent AF is when no further attempt at rhythm control is planned.
Adding IV magnesium to standard rate-control drugs is reasonable for rapid AF; IV amiodarone is reserved for critically ill or decompensated patients, remembering it may chemically cardiovert an unanticoagulated patient.
Left atrial appendage occlusion is reasonable for patients with CHA₂DS₂-VASc ≥ 2 who have a contraindication to long-term anticoagulation; about 90% of nonvalvular AF thrombi form in the appendage.
AF causes about 20–25% of all strokes; untreated, the overall annual risk of embolic stroke is about 3–5%.
Pill-in-the-pocket flecainide (300 mg if ≥ 70 kg) or propafenone (600 mg if ≥ 70 kg) suits recurrent paroxysmal AF without structural heart disease, given with an AV-nodal blocker to prevent 1:1 flutter.
Dronedarone should not be used for rate control in permanent AF with cardiovascular risk factors (increased events).
Ashman phenomenon: a short R-R interval after a long one produces an aberrantly conducted (usually RBBB-pattern) beat that mimics a PVC or VT.
Sinus rhythm does not cancel the stroke risk: the CHA₂DS₂-VASc score, not the rhythm strip, decides anticoagulation.
Sources · Merck Manual Professional — Atrial Fibrillation · Joglar JA et al. 2023 ACC/AHA/ACCP/HRS Guideline for the Diagnosis and Management of Atrial Fibrillation. Circulation 2024;149:e1–e156 · 2025 AHA Guidelines for CPR and ECC — Part 9: Adult Advanced Life Support (Circulation 2025; doi 10.1161/CIR.0000000000001376), cpr.heart.org text · Starter sheet built from the verified AGACNP fact map (facts reviewed 2026-10-15).