Cardioversion for Atrial Fibrillation – Evidence‑Based Recommendations

1. Indications for Cardioversion

• Immediate electrical cardioversion is required for patients with hemodynamic instability (e.g., ongoing myocardial ischemia, symptomatic hypotension, angina, or acute heart failure) because delaying therapy increases mortality. – American College of Cardiology; Class I, strong evidence. 1
• Elective cardioversion (planned rhythm restoration) should be performed only after at least 3 weeks of therapeutic anticoagulation before the procedure and a minimum of 4 weeks after, irrespective of whether electrical or pharmacological methods are used. – American College of Cardiology; Class I. 2

2. Anticoagulation Strategy

2.1 AF Duration ≥ 48 h or Unknown

• Standard approach: prescribe therapeutic anticoagulation (INR 2.0–3.0 for warfarin or approved NOAC dosing) for ≥ 3 weeks before and ≥ 4 weeks after cardioversion, regardless of the cardioversion modality.* – European Society of Cardiology*; Class I. 3
• NOACs (apixaban, rivaroxaban, dabigatran) are preferred over warfarin for peri‑cardioversion anticoagulation because they provide faster onset and comparable safety. – European Society of Cardiology; Class I. 4

2.2 TEE‑Guided Strategy (when 3‑week anticoagulation not feasible)

• Perform trans‑esophageal echocardiography to exclude left‑atrial or LAA thrombus. If no thrombus is seen, start IV heparin or LMWH immediately, proceed with cardioversion, and continue oral anticoagulation for ≥ 4 weeks. – European Society of Cardiology; Class IIa. 1
• If thrombus is detected, anticoagulate for 3–4 weeks, repeat TEE, and only cardiovert after thrombus resolution. – European Society of Cardiology; Class IIa. 5

2.3 AF Duration < 48 h

• High stroke risk (CHADS₂‑VASc ≥ 2 in men, ≥ 3 in women): give anticoagulation (heparin, factor Xa inhibitor, or direct thrombin inhibitor) before cardioversion and continue long‑term based on risk. – American College of Cardiology; Class IIa. 6
• Low stroke risk (CHADS₂‑VASc = 0 in men, = 1 in women): anticoagulation is optional for the procedure itself, but clinicians should consider patient‑specific factors. – American College of Cardiology; Class IIb. 6

2.4 Immediate Cardioversion in Hemodynamic Instability

• Do not delay cardioversion for anticoagulation; proceed immediately while initiating IV heparin bolus followed by infusion (target aPTT 1.5–2× control) or LMWH unless contraindicated. – European Society of Cardiology; Class I. 3
• Continue oral anticoagulation (INR 2.0–3.0 or NOAC) for at least 4 weeks after the procedure. – American College of Cardiology; Class I. 1

2.5 Post‑Cardioversion Anticoagulation Duration

• Long‑term anticoagulation decisions should be based on the patient’s CHADS₂‑VASc score and bleeding risk, not on whether sinus rhythm is maintained. – American College of Cardiology; Class I. 2
• 98 % of thromboembolic events occur within the first 10 days after cardioversion, and atrial mechanical stunning can persist for several weeks, justifying the minimum 4‑week anticoagulation period. – European Society of Cardiology. 3

3. Electrical Cardioversion Technique

• Use R‑wave‑synchronized direct‑current shock; biphasic waveforms are more effective than monophasic. – American College of Cardiology; Class I. 1
• Initial energy setting: 200 J for monophasic devices; biphasic devices may start at lower energies (e.g., 100–150 J) and titrate upward. – American College of Cardiology; Class I. 2

Contraindications (Class III)

• Digitalis toxicity – American College of Cardiology. 1
• Significant hypokalemia – American College of Cardiology. 1

Enhancing Success (Class IIa)

• Pre‑treatment with antiarrhythmic drugs (amiodarone, flecainide, ibutilide, propafenone, or sotalol) improves conversion rates and reduces early recurrence. – American College of Cardiology. 7

4. Pharmacological Cardioversion

4.1 First‑Line Agents (Class I)

Evidence from ACC and ESC guidelines. – American College of Cardiology; Class I. 2

4.2 “Pill‑in‑the‑Pocket” (Class IIa)

• A single oral dose of flecainide or propafenone can terminate AF outside the hospital after prior in‑hospital safety testing, provided the patient has no sinus/AV node disease, bundle‑branch block, prolonged QT, Brugada syndrome, or structural heart disease. – American College of Cardiology. 8
• Beta‑blocker or non‑dihydropyridine calcium‑channel blocker pretreatment is mandatory to prevent rapid ventricular response if atrial flutter occurs. – American College of Cardiology. 1

4.3 Agents to Avoid (Class III)

• Digoxin and sotalol are not recommended for acute pharmacological cardioversion because they may be ineffective or pro‑arrhythmic. – American College of Cardiology. 1

4.4 Contraindications for Pharmacological Cardioversion (Class III)

• Sinus node dysfunction, AV‑conduction disturbances, or QTc > 500 ms preclude use of class IC or class III agents. – European Society of Cardiology. 4

5. Rate Control Prior to Cardioversion

• First‑line agents: beta‑blockers (e.g., metoprolol, esmolol), non‑dihydropyridine calcium‑channel blockers (diltiazem, verapamil), and digoxin (especially in heart‑failure patients). – American College of Cardiology. 2
• Target heart rate: strict control < 80 bpm is reasonable for symptomatic patients; lenient control < 110 bpm may be acceptable in asymptomatic patients with preserved LV function. – American College of Cardiology. 9

6. Post‑Cardioversion Management

• Maintain anticoagulation for a minimum of 4 weeks after any cardioversion, then base long‑term therapy on CHADS₂‑VASc score rather than rhythm status. – American College of Cardiology; Class I. 3
• Consider chronic antiarrhythmic therapy (e.g., amiodarone, sotalol) to sustain sinus rhythm when the risk of recurrence is high. – American College of Cardiology. 1

Anticoagulation and Timing Strategies for Cardioversion in Atrial Fibrillation

Anticoagulation Duration for AF ≥ 48 h or Unknown

• Therapeutic anticoagulation should be given for ≥ 3 weeks before and ≥ 4 weeks after cardioversion, regardless of whether an electrical or pharmacological method is used. (Canadian Cardiovascular Society) 10
• When warfarin is selected, the target INR = 2.0–3.0. (Canadian Cardiovascular Society) 10
• The requirement for ≥ 3 weeks of pre‑procedure anticoagulation applies to all patients irrespective of CHA₂DS₂‑VASc score. (Canadian Cardiovascular Society) 10

Immediate Cardioversion Without Prior Anticoagulation

• The Canadian Cardiovascular Society permits immediate cardioversion without preceding anticoagulation for patients with a clearly documented AF onset ≤ 12 h, provided there is no recent stroke/TIA (within 6 months), or for patients with a CHADS₂ < 2 who present after 12 h but within 48 h. (Class I recommendation) 10
• The European Society of Cardiology allows early cardioversion without transesophageal echocardiography in patients with a definite AF duration < 48 h; this carries a Class IIa recommendation (conflicting evidence but weighted toward recommendation). 10

Guideline Recommendations for Cardioversion of Atrial Fibrillation Within and Beyond 48 Hours

1. Immediate Cardioversion for AF < 48 Hours

• Patients presenting with atrial fibrillation of < 48 hours duration may undergo immediate electrical or pharmacological cardioversion without a mandatory 3‑week pre‑procedural anticoagulation period, provided that therapeutic anticoagulation is started at presentation and continued for at least 4 weeks after cardioversion. [11][12]13

• The 48‑hour cutoff is based on the premise that left‑atrial thrombus formation requires time; cardioversion performed within this window is associated with a lower thromboembolic risk. [12][14]

• Recent data indicate that the safety of this approach is not absolute: in patients with AF < 48 hours who did not receive anticoagulation, the 30‑day stroke rate was 0.88 % versus 0.22 % in those who received therapeutic anticoagulation (≈5‑fold higher risk). 12

• In the ANTI‑Kogulation Registry, the incidence of left‑atrial thrombus was 4 % among un‑anticoagulated patients with AF < 48 hours, compared with 0 % in anticoagulated patients. 12

• Stroke after cardioversion has been reported even in patients with a CHADS₂ score of 0, demonstrating that “low‑risk” individuals are not exempt from thromboembolic complications. 12

2. Anticoagulation Strategy for All Patients (AF < 48 Hours)

• Initial therapy: At presentation, initiate therapeutic anticoagulation with unfractionated heparin, full‑dose low‑molecular‑weight heparin (VTE treatment dose), or a direct oral anticoagulant (NOAC) before proceeding to cardioversion. [13][15]

• Post‑cardioversion: Continue therapeutic oral anticoagulation for a minimum of 4 weeks after successful cardioversion, irrespective of baseline stroke risk or whether sinus rhythm is maintained. [13][15]

• Long‑term decision‑making: After the mandatory 4‑week period, determine the need for ongoing anticoagulation based on the patient’s CHA₂DS₂‑VASc score, not on the success or durability of rhythm restoration. [13][15]

3. Society‑Specific Risk‑Stratified Approaches (AF < 48 Hours)

3.1 Canadian Cardiovascular Society (more permissive)

• Immediate cardioversion without prior anticoagulation is allowed when the onset of AF is clearly documented ≤ 12 hours and there has been no stroke or transient ischemic attack within the preceding 6 months. 11

• For presentations between 12 and 48 hours, patients with a CHADS₂ score < 2 may be considered for immediate cardioversion without preceding anticoagulation. 11

3.2 European Society of Cardiology

• Early cardioversion without transesophageal echocardiography (TEE) is recommended for patients with a definite AF duration < 48 hours (Class IIa recommendation). [11][16]

3.3 American College of Chest Physicians (most conservative)

• Initiate anticoagulation at presentation with LMWH or UFH at full VTE treatment doses and proceed to cardioversion rather than delaying for a 3‑week therapeutic course. [13][15]

4. Management of AF ≥ 48 Hours or Unknown Duration

• Standard 3‑Week Pre‑Cardioversion Anticoagulation: Provide therapeutic anticoagulation (warfarin with INR 2.0‑3.0 or appropriate NOAC dosing) for ≥ 3 weeks before cardioversion and ≥ 4 weeks after, regardless of the method of cardioversion (electrical or pharmacological). [12][13][15][17]

• TEE‑Guided Alternative: Begin immediate therapeutic anticoagulation (IV heparin or full‑dose LMWH), perform TEE to exclude left‑atrial or left‑atrial‑appendage thrombus, and proceed with cardioversion only if no thrombus is visualized. [12][17]14

• Post‑procedure anticoagulation (both approaches): Continue oral anticoagulation for ≥ 4 weeks after cardioversion irrespective of the chosen strategy. [12][13]15

5. Emergency Cardioversion in Hemodynamically Unstable Patients

• When patients present with hemodynamic instability (e.g., ongoing myocardial ischemia, symptomatic hypotension, angina, or acute heart failure), cardioversion should be performed immediately without waiting for anticoagulation to achieve therapeutic levels. [18][19][15][17]

• Concurrent anticoagulation: Administer an IV heparin bolus followed by continuous infusion targeting an activated partial thromboplastin time of 1.5‑2 × control, or give full‑dose LMWH at presentation unless contraindicated; this should not delay the emergency procedure. [18][19][15][17]

• After successful emergency cardioversion, maintain therapeutic oral anticoagulation for at least 4 weeks. [13][15]

6. Post‑Cardioversion Thromboembolic Risk Considerations

• The traditional belief that AF < 48 hours carries negligible thromboembolic risk is challenged by contemporary data showing a 0.88 % 30‑day stroke rate in un‑anticoagulated patients—exceeding the accepted threshold for initiating anticoagulation (≥ 1.5 % per year or ≥ 0.12 % per 30 days). 12

• Atrial stunning: Mechanical function of the atria may remain impaired for several weeks after cardioversion (electrical, pharmacological, or spontaneous), creating a window for new thrombus formation despite restoration of sinus rhythm. [12][14]

• Timing of events: Approximately 98 % of thromboembolic events occur within the first 10 days after cardioversion, supporting the recommendation for a minimum 4‑week post‑procedure anticoagulation course. 19

• High‑risk subgroups: Patients with mechanical heart valves, rheumatic heart disease, or a recent stroke/TIA (within 6 months) should have cardioversion delayed to allow a full 3‑week therapeutic anticoagulation period even when AF duration is < 48 hours. [18][19]

• Uncertain AF duration: When the exact duration of AF is unknown, it should be managed as if it were ≥ 48 hours, requiring either the standard 3‑week anticoagulation regimen or a TEE‑guided approach before cardioversion. [12][13][15][17]

7. Preferred Anticoagulants for the Peri‑Cardioversion Period

• Direct oral anticoagulants (apixaban, rivaroxaban, dabigatran, edoxaban) are preferred over warfarin for peri‑cardioversion anticoagulation because they provide a rapid onset of action, predictable anticoagulant effect, comparable safety, and do not require routine INR monitoring. [13][15]16

Anticoagulation Strategies for Cardioversion in Atrial Fibrillation

General Principles

• The Canadian Cardiovascular Society (CCS) states that patients with atrial fibrillation (AF) of < 48 hours may undergo cardioversion without a mandatory 3‑week pre‑procedural anticoagulation, provided therapeutic anticoagulation is started at presentation and continued for at least 4 weeks after cardioversion. 20, 21

• Contemporary CCS evidence demonstrates that thromboembolic risk is not negligible even within the first 48 hours of AF onset. 21, 22

Risks Within the 48‑Hour Window

• In patients with AF < 48 h who were not anticoagulated, the 30‑day stroke rate was 0.88 %, compared with 0.22 % in those who received anticoagulation—a roughly five‑fold increase. 21

• The ANTI‑Kogulation Registry reported that 4 % of un‑anticoagulated patients with AF < 48 h had left‑atrial thrombus, versus 0 % in anticoagulated patients. 21

• Strokes occurred even in patients with a CHADS₂ score of 0, indicating that “low‑risk” status does not eliminate thromboembolic risk. 21

Management Based on AF Duration

AF < 48 Hours

• All patients should receive therapeutic anticoagulation at presentation, irrespective of the 48‑hour window. 20, 21

High Stroke‑Risk (CHADS₂‑VASc ≥ 2 in men, ≥ 3 in women)

• Initiate IV heparin, a factor Xa inhibitor, or a direct thrombin inhibitor immediately before cardioversion (American College of Cardiology recommendation). 23
• Continue oral anticoagulation for a minimum of 4 weeks after cardioversion. 20, 21, 23
• Long‑term anticoagulation decisions should be based on CHADS₂‑VASc score, not on rhythm status. 20, 21, 23

Lower‑Risk Patients

• Patients presenting ≤ 12 h after a clearly documented AF onset and without recent stroke/TIA may undergo immediate cardioversion without prior anticoagulation; however, anticoagulation should still be started at presentation and continued for at least 4 weeks. 20, 21
• Patients with CHADS₂‑VASc 0‑1 presenting 12‑48 h after onset may also undergo cardioversion without prior anticoagulation, but anticoagulation must be initiated immediately (preferably before cardioversion) and maintained for ≥ 4 weeks. 20, 21

AF ≥ 48 Hours or Unknown Duration

• Standard (preferred) approach: therapeutic anticoagulation for ≥ 3 weeks before cardioversion, followed by ≥ 4 weeks after the procedure. Target INR 2.0‑3.0 for warfarin; direct oral anticoagulants (DOACs) are preferred. 20, 24, 21, 25
• TEE‑guided alternative: start immediate therapeutic anticoagulation (IV heparin or LMWH), perform trans‑esophageal echocardiography to exclude left‑atrial/appendage thrombus, and if negative, proceed with cardioversion; if thrombus is present, continue anticoagulation for 3‑4 weeks, repeat TEE, then cardiovert. Anticoagulation is continued for ≥ 4 weeks regardless of the pathway. 20, 21, 22

Emergency Cardioversion (Hemodynamically Unstable Patients)

• The Society of Thoracic Surgeons (STS) advises that cardioversion must be performed immediately in patients with hemodynamic instability (e.g., ongoing myocardial ischemia, symptomatic hypotension, acute heart failure) without delaying for anticoagulation. 26, 24, 25
• Concurrently or immediately after, administer an IV heparin bolus followed by continuous infusion (target aPTT 1.5‑2 × control) or LMWH when feasible. 26, 24, 25
• Continue therapeutic oral anticoagulation for at least 4 weeks post‑cardioversion. 26, 24, 25

Post‑Cardioversion Anticoagulation

• All patients, regardless of AF duration, cardioversion method, or maintenance of sinus rhythm, require a minimum of 4 weeks of therapeutic anticoagulation after cardioversion. 20, 24, 21, 25, 23

Preferred Anticoagulants

• DOACs (apixaban, rivaroxaban, dabigatran, edoxaban) are preferred over warfarin for peri‑cardioversion anticoagulation (CCS recommendation). 20, 21, 27
• DOACs are associated with a lower rate of stroke/systemic embolism compared with warfarin (0.2 % vs 0.6 %). 20
• Bleeding rates with DOACs are similar to those of warfarin. 20

Special Populations Requiring 3‑Week Pre‑Cardioversion Anticoagulation Even When AF < 48 Hours

• Patients with mechanical heart valves, rheumatic heart disease, recent stroke/TIA (≤ 6 months), or CHADS₂ ≥ 3 should receive ≥ 3 weeks of therapeutic anticoagulation before cardioversion, regardless of AF duration. 24, 25

Common Pitfalls (Guideline‑Based Corrections)

• Assuming safety without anticoagulation: Even within 48 hours, the stroke risk exceeds the threshold for anticoagulation initiation (≥ 1.5 % per year or ≥ 0.12 % per 30 days). 21
• Basing long‑term anticoagulation on rhythm: Ongoing anticoagulation decisions must be guided by CHADS₂‑VASc score, not by whether sinus rhythm is maintained. 20, 24, 21, 23
• Delaying emergency cardioversion for anticoagulation: In hemodynamically unstable patients, cardioversion should never be postponed; anticoagulation should be given concurrently or immediately after. 26, 24, 25
• Treating unknown AF duration as < 48 hours: When duration is uncertain, manage as ≥ 48 hours, requiring either 3‑week anticoagulation or a TEE‑guided strategy. 24, 25

Cardioversion for Atrial Fibrillation – Evidence‑Based Recommendations

1. Emergency (Immediate) Cardioversion

• Indications for immediate synchronized DC shock – Hemodynamic instability (ongoing myocardial ischemia, symptomatic hypotension, angina, or acute heart‑failure) warrants emergency cardioversion without awaiting anticoagulation. Class I recommendation【28】【29】【30】【31】
• WPW‑related rapid AF – Patients with pre‑excitation (Wolff‑Parkinson‑White) who develop very rapid ventricular response or hemodynamic compromise should be cardioverted immediately. Class I【28】【29】
• Anticoagulation during emergency cardioversion – Give an IV heparin bolus followed by continuous infusion (target aPTT 1.5–2 × control) or a full‑dose LMWH concurrently; do not delay the shock. Class I【28】【31】
• Post‑procedure anticoagulation – Continue therapeutic oral anticoagulation for ≥ 4 weeks after the emergency cardioversion, irrespective of rhythm outcome. Class I【28】【31】

2. Anticoagulation Strategy by AF Duration

2.1 AF < 48 h

• Thrombo‑embolic risk exists even within 48 h – 30‑day stroke rate is 0.88 % without anticoagulation vs 0.22 % with it (≈ 5‑fold increase); left‑atrial thrombus occurs in 4 % of untreated patients. Evidence Level B【32】
• Therapeutic anticoagulation at presentation – Initiate IV heparin, therapeutic‑dose LMWH, or a NOAC before cardioversion. Class I【32】
• Minimum 4‑week post‑cardioversion anticoagulation – Required regardless of rhythm maintenance. Class I【28】【31】
• High‑risk sub‑group – Patients with mechanical valves, rheumatic disease, recent stroke/TIA (<6 mo) or CHADS₂ ≥ 3 need ≥ 3 weeks of therapeutic anticoagulation before cardioversion, even if AF < 48 h. Class IIa【33】
• More permissive Canadian pathway – If AF onset ≤ 12 h and no recent stroke/TIA, immediate cardioversion is allowed without prior anticoagulation, but anticoagulation must start at presentation. Class IIa【32】
• CHADS₂ < 2 and onset 12–48 h – Immediate cardioversion without prior anticoagulation is acceptable. Class IIa【32】

2.2 AF ≥ 48 h or Unknown Duration

• Standard pre‑cardioversion anticoagulation – Provide therapeutic anticoagulation for ≥ 3 weeks (warfarin INR 2.0–3.0 or appropriate NOAC dosing) before cardioversion. Class I【28】【29】【30】【31】
• Continue anticoagulation ≥ 4 weeks after cardioversion – Applies to both electrical and pharmacological strategies. Class I【28】【29】【30】【31】
• TEE‑guided alternative – Start immediate therapeutic anticoagulation, perform transesophageal echocardiography to rule out left‑atrial/appendage thrombus; if negative, proceed with cardioversion and maintain anticoagulation ≥ 4 weeks; if thrombus present, continue anticoagulation 3–4 weeks, repeat TEE, then cardiovert. Class IIa【33】

2.3 Preferred Anticoagulant

• NOACs over warfarin – NOACs are favored for peri‑cardioversion anticoagulation because of rapid onset, predictable effect, and comparable safety; they are associated with a lower stroke/systemic embolism rate (0.2 % vs 0.6 % with warfarin). Evidence Level B【33】

3. Electrical Cardioversion Technique

• R‑wave‑synchronized direct‑current shock is the recommended method. Class I【28】【29】【30】【31】
• Antiarrhythmic pretreatment – Administration of amiodarone, flecainide, ibutilide, propafenone, or sotalol before shock improves conversion success and reduces early recurrence. Class IIa【28】【29】【30】【31】
• Absolute contraindications – Digitalis toxicity and significant hypokalemia preclude cardioversion. Class III【28】【29】【30】【31】
• Avoid frequent repeat shocks in patients who regain sinus rhythm only briefly despite prophylactic antiarrhythmic therapy. Class IIb【28】【29】【30】【31】

4. Pharmacological Cardioversion

4.1 First‑Line Agents

4.2 “Pill‑in‑the‑Pocket”

• Single oral dose of flecainide or propafenone can be self‑administered after documented in‑hospital safety testing, provided the patient has no sinus/AV‑node disease, bundle‑branch block, QT prolongation, Brugada syndrome, or structural heart disease. Class IIa【29】【30】【31】
• Mandatory pretreatment with a β‑blocker or non‑dihydropyridine calcium‑channel blocker to prevent rapid ventricular response if atrial flutter occurs. Class IIa【29】【30】【31】

4.3 Agents to Avoid

• Digoxin and sotalol are harmful for pharmacological cardioversion. Class III【28】【29】【30】【31】
• Quinidine and procainamide have uncertain benefit (Class IIb). Class IIb【28】【29】【30】【31】

4.4 Special Considerations for Ibutilide

• Conversion rates: AFL 50‑75 %, AF 30‑50 % within 30‑60 min. Class IIa【34】
• Torsades de pointes risk ≈ 2‑3 %; avoid in prolonged QTc, HF, reduced EF, electrolyte disturbances. Class III【34】
• High‑dose IV magnesium (4 g) before ibutilide may improve conversion and lower TdP risk. Class IIa【34】
• Continuous ECG monitoring for at least 4 h after administration. Class I【34】

4.5 Vernakalant Details

• Overall conversion 59 % with median time 12 min. Class IIa【34】
• Contraindications: hypotension, severe HF (NYHA III/IV), recent ACS, severe aortic stenosis. Class III【34】
• Common adverse effects: dysgeusia, paresthesia, nausea. Class IIa【34】

5. Post‑Cardioversion Management

• Mandatory anticoagulation – All patients require ≥ 4 weeks of therapeutic anticoagulation after cardioversion, independent of AF duration, cardioversion method, or maintenance of sinus rhythm. Class I【28】【31】
• Long‑term anticoagulation – Continue indefinitely if AF recurs or persists; if sinus rhythm is maintained for ≥ 4 weeks, reassess anticoagulation need based on CHADS₂‑VASc score. Class IIa【33】
• Repeat cardioversion – In patients who relapse after successful conversion, a repeat procedure is permissible after instituting prophylactic antiarrhythmic therapy. Class IIa【28】【29】【30】【31】

6. Practical Pitfalls

• Do not postpone emergency cardioversion for anticoagulation; give anticoagulation concurrently. Class I【28】【31】
• Avoid digoxin or sotalol for acute cardioversion—they are ineffective or potentially harmful. Class III【28】【29】【30】【31】
• Digitalis toxicity or significant hypokalemia are absolute contraindications to cardioversion. Class III【28】【29】【30】【31】

Initiation and Management of Anticoagulation in New‑Onset Atrial Fibrillation

Risk Stratification and Immediate Therapy

• Initiate oral anticoagulation at the time of diagnosis in all patients with new‑onset atrial fibrillation who have a CHA₂DS₂‑VASc score ≥ 2 (men) or ≥ 3 (women), provided there is no active bleeding or absolute contraindication. 35, 36
• For patients meeting the high‑risk thresholds (CHA₂DS₂‑VASc ≥ 2 men, ≥ 3 women), start anticoagulation without delay, using a direct oral anticoagulant (DOAC) as first‑line therapy rather than warfarin. 35, 36
• DOACs (apixaban, rivaroxaban, dabigatran, edoxaban) achieve therapeutic effect within hours and do not require the 3‑week lead‑in period necessary for warfarin. 35
• Anticoagulation should not be postponed for cardioversion planning, rhythm‑control attempts, or outpatient follow‑up. 36
• In patients with lower stroke risk (CHA₂DS₂‑VASc 0‑1 men, 1‑2 women), anticoagulation decisions must balance individual bleeding risk and patient preferences, but the threshold for initiating therapy remains low. 36

Timing of Anticoagulation Around Cardioversion

AF Duration < 48 Hours

• Begin therapeutic anticoagulation immediately (intravenous heparin, therapeutic‑dose LMWH, or a DOAC) before performing cardioversion, even when the arrhythmia has been present for less than 48 hours. 36
• Continue anticoagulation for at least 4 weeks after cardioversion regardless of whether sinus rhythm is maintained. 36

AF Duration ≥ 48 Hours or Unknown Onset

• Standard pathway: Provide therapeutic anticoagulation for ≥ 3 weeks before cardioversion, then maintain anticoagulation for ≥ 4 weeks after the procedure (warfarin target INR 2.0‑3.0 or appropriate DOAC dosing). 36
• TEE‑guided pathway: Start immediate therapeutic anticoagulation, perform transesophageal echocardiography to exclude left‑atrial/appendage thrombus; if negative, proceed with cardioversion and continue anticoagulation for ≥ 4 weeks thereafter. 36

Hemodynamically Unstable Patients

• Perform immediate cardioversion without waiting for anticoagulation in patients with ongoing myocardial ischemia, symptomatic hypotension, angina, or acute heart failure; give concurrent anticoagulation. 35, 36
• Administer an intravenous heparin bolus followed by continuous infusion (target aPTT 1.5‑2 × control) or therapeutic‑dose LMWH concurrently with or immediately after the procedure. 36
• Maintain therapeutic oral anticoagulation for at least 4 weeks after the emergency cardioversion. 36

Long‑Term Anticoagulation Strategy

• Ongoing anticoagulation decisions should be based on the CHA₂DS₂‑VASc score alone, not on rhythm status (e.g., sinus rhythm after cardioversion or ablation). 35, 36
• The perceived success of cardioversion or catheter ablation must never dictate discontinuation of anticoagulation. 35, 36
• After the mandatory 4‑week post‑cardioversion period, continue anticoagulation indefinitely if the patient’s stroke‑risk score warrants it. 36

Preferred Anticoagulant Choice

• DOACs are recommended over warfarin for stroke prevention in eligible patients with atrial fibrillation. 35, 36
• In patients who also require antiplatelet therapy (e.g., for acute coronary syndrome), a DOAC is preferred to warfarin to reduce bleeding risk. 35