How do you administer direct current cardioversion to a patient with intraoperative atrial fibrillation and left ventricular dysfunction?

Direct Current Cardioversion Administration for Intraoperative Atrial Fibrillation with Left Ventricular Dysfunction

For a patient with intraoperative atrial fibrillation and left ventricular dysfunction, immediate R-wave synchronized direct current cardioversion is the definitive treatment, as hemodynamic instability in this setting mandates electrical rather than pharmacological conversion. 1

Immediate Indications in the Intraoperative Setting

Proceed directly to electrical cardioversion without delay when:

• Symptomatic hypotension develops 1, 2
• Ongoing myocardial ischemia is present 1, 2
• Heart failure symptoms emerge or worsen 1
• The rapid ventricular response fails to respond promptly to pharmacological rate control 1

The intraoperative setting with left ventricular dysfunction creates inherent hemodynamic vulnerability, making immediate cardioversion a Class I recommendation with Level of Evidence C. 1

Critical Pre-Cardioversion Contraindication Check

Verify absence of the following absolute contraindications before proceeding:

• Digitalis toxicity (contraindicated) 1, 2
• Hypokalemia (contraindicated) 1

These conditions can precipitate ventricular arrhythmias during cardioversion and must be corrected first if present. 1

Technical Procedure for Cardioversion

Equipment Setup and Energy Selection

Use biphasic waveform defibrillators with initial energy of 200 J:

• Biphasic waveforms are superior to monophasic and require less total energy 1, 3
• For monophasic defibrillators, start with 300-360 J 3
• Initial energy of 100 J is inadequate and should be avoided 1

Electrode placement:

• Anteroposterior position is more effective than anterolateral placement 1
• Use electrode paddles 8-12 cm in diameter to optimize current density 1, 2
• Position at least 8 cm from any implanted pacemaker or defibrillator 1

Synchronization and Shock Delivery

Ensure proper R-wave synchronization:

• The shock must be synchronized with the QRS complex to avoid delivering energy during the vulnerable period of the cardiac cycle 1, 4, 2
• Select an ECG lead that clearly displays both the R wave and atrial activity 1
• Failure to synchronize can induce ventricular fibrillation 4

Deliver shock during expiration or with chest compression:

• This technique provides greater energy delivery to the heart 4

Escalation Protocol if Initial Shock Fails

Follow this two-shock protocol:

• If 200 J biphasic shock fails, immediately deliver 360 J 5, 3
• This approach reduces total energy delivered and procedure time compared to multiple incremental shocks 5
• Avoid frequent repetitive shocks beyond this protocol 1, 2

Sedation Requirements

Administer adequate procedural sedation:

• Use intravenous midazolam and/or propofol for conscious sedation 2
• In the intraoperative setting, coordinate with anesthesia for appropriate sedation depth
• General anesthesia or heavy sedation is required for patient comfort 3

Anticoagulation Considerations in Emergency Cardioversion

Do not delay cardioversion for anticoagulation in hemodynamically unstable patients:

• Immediate cardioversion takes precedence over anticoagulation timing 6
• Administer heparin concurrently with initial IV bolus followed by continuous infusion (aPTT 1.5-2 times control) unless contraindicated 6
• The standard 3-week pre-cardioversion anticoagulation requirement does not apply to emergency situations 1, 2

Post-Cardioversion Management

Immediate post-shock monitoring:

• Assess for return to sinus rhythm immediately 1
• Monitor for prolonged sinus arrest, particularly in elderly patients with structural heart disease 1
• Watch for post-cardioversion arrhythmias including ventricular tachycardia 1

Anticoagulation continuation:

• Initiate or continue therapeutic anticoagulation for at least 4 weeks post-cardioversion (INR 2.0-3.0) 1, 6
• This applies regardless of whether cardioversion was successful 1

Antiarrhythmic prophylaxis for left ventricular dysfunction:

• Amiodarone is the preferred antiarrhythmic agent for patients with left ventricular dysfunction 1, 2
• Pretreatment with amiodarone enhances cardioversion success and prevents immediate recurrence (Class IIa, Level B) 1
• Avoid flecainide and propafenone in patients with structural heart disease or heart failure 1

Common Pitfalls to Avoid

Do not use pharmacological cardioversion as first-line in hemodynamically unstable patients:

• Digoxin and sotalol are harmful for acute cardioversion and should never be used 1
• Pharmacological agents cause delays that are unacceptable in unstable patients 1

Avoid starting with inadequate energy:

• Initial shocks of 100 J have only 14% success rates and require more total energy delivery 1
• Starting with 200 J (biphasic) achieves 54% immediate success 5

Do not perform cardioversion in the presence of device-related thrombus:

• If transesophageal echocardiography shows thrombus, treat with anticoagulation for 6-8 weeks before cardioversion 7

Special Considerations for Implanted Devices

For patients with pacemakers or defibrillators:

• Position paddles at least 8 cm from the device generator 1
• Use anteroposterior positioning 1
• Interrogate and reprogram the device before and after cardioversion 1
• Anticipate potential increase in pacing threshold requiring careful monitoring 1