Synchronized Cardioversion for Arrhythmias

Immediate Indications

The American Heart Association recommends synchronized cardioversion for hemodynamically unstable patients with supraventricular or ventricular tachycardia, and for stable patients when pharmacological therapy fails or is contraindicated 1, 2
Synchronized cardioversion should be performed immediately for patients exhibiting signs of hemodynamic instability, including hypotension, altered mental status, shock, chest pain, or acute heart failure symptoms, as recommended by the American College of Cardiology 3, 4

The American Heart Association suggests using synchronized cardioversion for AVRT if vagal maneuvers or adenosine are ineffective or not feasible in unstable patients 1, 2
The American College of Cardiology recommends immediate synchronized cardioversion for pre-excited atrial fibrillation in unstable patients, as rapid pre-excited AV conduction can lead to ventricular fibrillation 1, 2
The American Heart Association recommends starting with 100J (biphasic or monophasic) for unstable patients with monomorphic ventricular tachycardia with pulse 5, 3
Immediate synchronized cardioversion is indicated for wide complex tachycardia when hemodynamic instability is present, according to the American College of Cardiology 4
The American College of Cardiology recommends synchronous cardioversion at relatively low energies (50-100J biphasic) for supraventricular tachycardia in acute heart failure 6

The American Heart Association recommends using synchronized cardioversion when pharmacological therapy is ineffective or contraindicated in stable patients with adequate sedation or anesthesia 1, 2
The American College of Cardiology suggests that most stable patients with AVRT or AVNRT respond to pharmacological therapy, but synchronized cardioversion is highly effective when drugs fail 1, 2

The American Heart Association advises against using synchronized cardioversion for ventricular fibrillation, as the device may not sense a QRS wave, potentially resulting in no shock delivery 5
The American College of Cardiology recommends treating pulseless ventricular tachycardia exactly like VF with unsynchronized high-energy shocks to avoid delays in cardiac arrest treatment 5
The American Heart Association suggests avoiding synchronized cardioversion for polymorphic ventricular tachycardia, even with a pulse, as synchronization is usually not possible 5
The American College of Cardiology recommends against electrical cardioversion in patients with digitalis toxicity or hypokalemia 3

The American Heart Association recommends an initial energy level of 100J (biphasic or monophasic) for monomorphic ventricular tachycardia with pulse 5
The American College of Cardiology suggests an initial energy level of 50-100J (biphasic) for supraventricular tachycardia or atrial flutter 6
The American Heart Association recommends standard cardioversion energies with stepwise escalation if the initial attempt fails for AVRT or AVNRT 1, 2

The American College of Cardiology advises against delaying cardioversion in hemodynamically unstable patients to attempt pharmacological conversion, as this prioritizes morbidity and mortality outcomes 4
The American Heart Association recommends avoiding calcium channel blockers in patients with ventricular tachycardia, as they can worsen hemodynamic status 4
The American College of Cardiology suggests having equipment immediately available when treating unstable ventricular tachycardia, as patients may deteriorate to pulseless VT or VF at any moment 5
The American Heart Association recommends being prepared for post-cardioversion arrhythmias, as patients often have atrial or ventricular premature complexes immediately after cardioversion that may induce further episodes 1, 2

The American College of Cardiology recommends considering antiarrhythmic medication, such as amiodarone, to prevent recurrent arrhythmias 3
The American Heart Association suggests that beta-blockers may be beneficial for recurrent and refractory ventricular arrhythmias 3

The American Heart Association recommends identifying signs of instability requiring immediate cardioversion, such as acute altered mental status, ischemic chest discomfort, acute heart failure, hypotension, or other signs of shock, in patients undergoing synchronized cardioversion 7, 8
For patients with ventricular rates <150 beats per minute without ventricular dysfunction, the tachycardia is more likely secondary to an underlying condition rather than the cause of instability, according to the American College of Cardiology 7
The American Heart Association advises not to delay cardioversion in extremely unstable patients to establish IV access or provide sedation—proceed immediately 7

The American Heart Association recommends establishing intravenous access before cardioversion if possible, and administering procedural sedation or anesthesia in conscious, hemodynamically stable patients 7, 8
The American College of Cardiology suggests turning on the synchronization function on the defibrillator to time shock delivery with the QRS complex, and verifying that the device is detecting QRS complexes appropriately before proceeding 7
For atrial fibrillation, the American College of Cardiology recommends an initial biphasic energy of 120-200 J (Class IIa recommendation) 9
For monomorphic ventricular tachycardia with pulse, the American Heart Association recommends an initial energy of 100 J (biphasic or monophasic) 7

The American College of Cardiology advises that if initial shock fails, increase energy in a stepwise fashion for subsequent attempts, and escalate biphasic energy beyond 200 J as needed for atrial fibrillation 9, 7
The American College of Cardiology recommends considering antiarrhythmic pretreatment (amiodarone, flecainide, ibutilide, propafenone, or sotalol) to enhance cardioversion success and prevent recurrent AF 9
The American College of Cardiology suggests not using frequent repetitive cardioversion in patients with short sinus rhythm periods between relapses despite antiarrhythmic therapy 9