What are the steps for synchronized cardioversion according to Canadian guidelines?

Synchronized Cardioversion Procedure Steps

For synchronized cardioversion in Canadian practice, immediately assess hemodynamic stability, establish IV access, provide procedural sedation (unless critically unstable), activate the synchronization mode on the defibrillator, select appropriate energy levels based on the arrhythmia type, and deliver the shock during the QRS complex. 1, 2

Pre-Procedure Assessment and Preparation

Hemodynamic Stability Evaluation

• Identify signs of instability requiring immediate cardioversion: acute altered mental status, ischemic chest discomfort, acute heart failure, hypotension, or other signs of shock. 1
• 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. 1
• Do not delay cardioversion in extremely unstable patients to establish IV access or provide sedation—proceed immediately. 1

Anticoagulation Considerations (Canadian Context)

• For AF/atrial flutter <48 hours duration with CHADS₂ score 0-1: cardioversion may proceed without prior anticoagulation in the emergency department setting. 3
• For AF/atrial flutter >48 hours or uncertain duration: therapeutic anticoagulation for 3 weeks before and 4 weeks after cardioversion is required. 3
• Recent Canadian evidence challenges historical conventions about omitting anticoagulation in low-risk patients undergoing cardioversion. 4

Contraindications to Verify

• Absolute contraindications: digitalis toxicity and hypokalemia. 1
• Never use synchronized mode for: ventricular fibrillation (device may not sense QRS and fail to deliver shock), pulseless ventricular tachycardia (delays treatment), or polymorphic ventricular tachycardia (synchronization not possible). 5, 2

Procedural Steps

Step 1: Establish IV Access and Sedation

• Establish intravenous access before cardioversion if possible. 1
• Administer procedural sedation or anesthesia in conscious, hemodynamically stable patients. 1, 2
• In hemodynamically unstable patients, proceed without delay for sedation. 2

Step 2: Activate Synchronization Mode

• Turn on the synchronization function on the defibrillator to time shock delivery with the QRS complex. 1
• This avoids shock delivery during the relative refractory period of the cardiac cycle, which could produce ventricular fibrillation. 1
• Verify that the device is detecting QRS complexes appropriately before proceeding. 1

Step 3: Select Initial Energy Dose

For Atrial Fibrillation:

• Initial biphasic energy: 120-200 J (Class IIa recommendation). 1
• Initial monophasic energy: 200 J. 1

For Atrial Flutter and Other SVTs:

• Initial energy: 50-100 J (often sufficient for these rhythms). 1, 2

For Monomorphic Ventricular Tachycardia with Pulse:

• Initial energy: 100 J (biphasic or monophasic). 1, 5, 2

Step 4: Position Electrodes

• Standard anterolateral or anteroposterior pad placement. 6
• If initial attempts fail, consider alternative electrode positions as part of a stepwise protocol. 6

Step 5: Deliver Synchronized Shock

• Ensure all personnel are clear of the patient before delivering the shock. 1
• Press and hold the shock button—there may be a brief delay as the device waits to synchronize with the next QRS complex. 1
• Verify return to sinus rhythm immediately after shock delivery. 1

Step 6: Energy Escalation if Needed

• If initial shock fails, increase energy in a stepwise fashion for subsequent attempts. 1, 5
• For atrial fibrillation: escalate biphasic energy beyond 200 J as needed. 1
• For atrial flutter/SVT: escalate from initial 50-100 J dose. 1
• For monomorphic VT: escalate from initial 100 J dose. 1

Post-Cardioversion Management

Immediate Monitoring

• Be prepared for post-cardioversion arrhythmias: atrial or ventricular premature complexes commonly occur immediately after cardioversion and may trigger recurrent episodes. 2
• Have equipment immediately available, as patients may deteriorate to pulseless VT or ventricular fibrillation. 2

Preventing Recurrence

• Consider antiarrhythmic pretreatment (amiodarone, flecainide, ibutilide, propafenone, or sotalol) to enhance cardioversion success and prevent recurrent AF. 1
• For patients who relapse after successful cardioversion, repeat the procedure following prophylactic antiarrhythmic medication administration. 1

Discharge Planning (Canadian ED Context)

• Canadian evidence demonstrates that most patients with recent-onset AF/AFL can be safely managed and discharged from the emergency department without hospital admission. 3
• An electrical-first strategy results in significantly shorter ED length of stay (median 3.5 hours vs 5.1 hours for chemical-first) with similar safety profiles. 7
• Ensure adequate follow-up to identify structural heart disease and evaluate need for long-term antithrombotic or antiarrhythmic therapy. 3

Critical Pitfalls to Avoid

• Never use synchronized cardioversion for ventricular fibrillation—the device may fail to deliver any shock. 5, 2
• Never delay cardioversion in hemodynamically unstable patients to attempt pharmacological conversion first. 2
• Avoid calcium channel blockers in ventricular tachycardia—they can worsen hemodynamic status. 2
• Do not use frequent repetitive cardioversion in patients with short sinus rhythm periods between relapses despite antiarrhythmic therapy. 1