Pharmacological (intravenous) cardioversion of atrial fibrillation

Pharmacological (intravenous) cardioversion is used for acute cardioversion of atrial fibrillation (AF).

Indications for pharmacological (intravenous) cardioversion of AF:

Before pharmacological (intravenous) cardioversion, left atrial thrombus must be excluded:

If the patient has a first-ever AF episode lasting <24 hours, cardioversion may be considered without thrombus exclusion.

AF duration <24 hours based on symptoms cannot be confirmed with absolute certainty,
because the patient may have asymptomatic AF paroxysms.

Contraindications

Digoxin intoxication (arrhythmias due to increased automaticity may worsen after cardioversion)
Hypokalaemia (<3.2 mmol/l)
Atrial thrombus (most commonly in the left atrial appendage)
INR >4.5

Relative contraindications

Acute critical condition (sepsis, myocardial infarction, etc.) or risk state (alcohol, drugs, stress, etc.)

Antiarrhythmic drugs used for (intravenous) cardioversion of AF:

Antiarrhythmic drugs for cardioversion of atrial fibrillation (intravenous)
Antiarrhythmic drug	Class	Time to conversion	Success rate	Typical patient
Propafenone	IC	< 6 h	43–89 %	Patient without structural heart disease
Flecainide	IC	< 6 h	52–95 %	Patient without structural heart disease
Amiodarone	III	6–8 h	44–80 %	Patient with structural heart disease / HFrEF
Vernakalant	III	< 10 min	50–70 %	Recent-onset AF (< 7 days)
Ibutilide	III	30–90 min (AF) < 60 min (atrial flutter)	30–50 % (AF) 60–75 % (atrial flutter)	AF or atrial flutter, including pre-excited AF
Procainamide	IA	< 30 min	50–75 %	AF with pre-excitation

Class IC antiarrhythmic drugs and 1:1 conducted atrial flutter

Class IC antiarrhythmic drugs slow conduction in the atrial myocardium.
In AF, chaotic electrical activity may slow and organize into a regular re-entry circuit.
The result is atrial flutter (often with a lower atrial rate of ~200/min).

The AV node may conduct this “slower” flutter with 1:1 AV conduction.
This results in 1:1 conducted atrial flutter with a ventricular rate of ~200/min.

To prevent 1:1 conducted atrial flutter, Class IC antiarrhythmic drugs should be administered together with drugs that slow AV nodal conduction:

Prevention of 1:1 conducted atrial flutter before Class IC administration (propafenone, flecainide)
Drug	Route	Dose	Timing before Class IC
Metoprolol	oral	25 mg	30 min before Class IC administration
Metoprolol	intravenous	5 mg administered over 1–2 minutes	20 min before Class IC administration
Verapamil	oral	80 mg	30 min before Class IC administration
Verapamil	intravenous	5 mg administered over 1–2 minutes	5 min before Class IC administration
Diltiazem	oral	60 mg	30 min before Class IC administration
Diltiazem	intravenous	15 mg administered over 1–2 minutes	5 min before Class IC administration

In pre-excited AF, antiarrhythmic drugs that prolong the effective refractory period (ERP) of the accessory pathway are recommended:

Procainamide (Class IA)
Ibutilide (Class III)
Electrical cardioversion (in case of hemodynamic instability) – vital indication.

In pre-excited AF, antiarrhythmic drugs that slow AV nodal conduction are contraindicated.

If AV nodal conduction is slowed, AF impulses may preferentially conduct to the ventricles via the accessory pathway,
with a risk of ventricular fibrillation and sudden cardiac death.

Contraindicated antiarrhythmic drugs – pre-excited atrial fibrillation
Drug	Class	Reason contraindicated
Verapamil, diltiazem	IV (Ca²⁺ channel blockers)	Slow only the AV node → increase conduction via the accessory pathway
Beta-blockers	II	Slow the AV node → risk of rapid 1:1 conduction over the accessory pathway
Digoxin	Inotropic agent, AV nodal blocker	Increases parasympathetic tone → AV nodal slowing, preferential accessory pathway conduction
Adenosine	AV nodal blocker	Blocks the AV node → allows rapid impulse conduction via the accessory pathway
Amiodarone (intravenous)	III	Unpredictable effect on the accessory pathway, risk of accelerated conduction

Maintenance of sinus rhythm (SR) after cardioversion, despite antiarrhythmic therapy, is individual.

SR persists in 50–90% of patients (first 3 months).
Elimination of AF risk factors and triggers is essential (sometimes difficult: stress, sleep deprivation).

Atropine dosing for bradycardia after AF cardioversion:

Pharmacological (intravenous) cardioversion of atrial fibrillation	Class
Left atrial thrombus is considered excluded if all of the following criteria are met: Non-valvular newly diagnosed AF lasting < 24 hours (based on symptoms) CHA₂DS₂-VA score 0–1 No history of TIA or stroke EF > 50 %	I
Flecainide or propafenone (intravenous) are recommended for pharmacological cardioversion of atrial fibrillation in patients without structural heart disease.	I
Before administration of Class IC antiarrhythmic drugs (flecainide, propafenone), AV nodal–blocking agents (beta-blocker, verapamil, diltiazem) should be administered to prevent 1:1 conducted atrial flutter.	IIa
Vernakalant (intravenous) is recommended for pharmacological cardioversion of atrial fibrillation in patients with EF >40%, without myocardial infarction within the last 30 days and without severe aortic stenosis.	I
Amiodarone (intravenous) is recommended for pharmacological cardioversion of atrial fibrillation in patients with structural heart disease.	I
Pharmacological cardioversion is not recommended in patients (without a pacemaker) who have: sick sinus syndrome, second- or third-degree AV block, QTc interval > 500 ms.	III
In pre-excited AF, the following are contraindicated: Adenosine Verapamil Diltiazem Beta-blockers Digoxin Amiodarone	III