What is the procedure for performing synchronized cardioversion on a patient with rheumatic heart disease and atrial fibrillation with rapid ventricular response and tachycardia?

How to Perform Synchronized Cardioversion

Synchronized cardioversion is performed by delivering an R-wave synchronized electrical shock to restore normal rhythm, with immediate cardioversion required for hemodynamically unstable patients and elective cardioversion appropriate for stable patients when pharmacological therapy fails or is contraindicated. 1

Indications for Synchronized Cardioversion

Immediate (Emergent) Indications

• Hemodynamic instability with any of the following signs: 1, 2
  • Symptomatic hypotension
  • Ongoing myocardial ischemia or angina
  • Acute heart failure symptoms
  • Altered mental status or signs of shock
• Pre-excited atrial fibrillation (Wolff-Parkinson-White) with rapid ventricular response, regardless of stability 1

Elective Indications

• Hemodynamically stable patients with atrial fibrillation when symptoms are unacceptable despite rate control 1
• Stable supraventricular tachycardia when pharmacological therapy (vagal maneuvers, adenosine, AV nodal blockers) is ineffective or contraindicated 1
• As part of long-term rhythm control strategy for recurrent symptomatic atrial fibrillation 1

Pre-Procedure Preparation

Patient Assessment

• Verify hemodynamic status by checking blood pressure, mental status, presence of chest pain, and signs of heart failure 3, 2
• Obtain 12-lead ECG to confirm rhythm and assess for pre-excitation patterns 4
• Ensure resuscitation equipment is immediately available, including defibrillator capability for unsynchronized shocks if ventricular fibrillation occurs 1

Sedation Protocol

• Provide adequate sedation or anesthesia for all conscious patients, even those who are hypotensive 1, 4
• For hemodynamically unstable patients, use rapid-acting sedation immediately before shock delivery 4

Contraindications to Check

• Digitalis toxicity - absolute contraindication 1, 3
• Hypokalemia - absolute contraindication; correct before proceeding 1, 3

Technical Procedure

Equipment Setup

• Use biphasic waveform defibrillators when available, as they are more effective than monophasic 5
• Select paddle/pad size of 8-12 cm diameter for optimal current delivery 1
• Apply electrolyte-impregnated pads to minimize skin resistance 1

Electrode Placement

• Position electrodes in anterolateral or anteroposterior configuration 1
• Consider adjusting electrode position if initial attempts fail 3
• Apply firm pressure over electrodes to reduce thoracic impedance 3

Synchronization and Energy Selection

• Activate R-wave synchronization mode to ensure shock delivery occurs outside the vulnerable period of the cardiac cycle 1
• Deliver shock during expiration or with chest compression to maximize energy delivery to the heart 1
• For atrial fibrillation, start with appropriate energy levels based on device capabilities 1

Post-Cardioversion Management

Immediate Monitoring

• Monitor continuously for recurrence, as atrial or ventricular premature complexes immediately after cardioversion may reinitiate tachycardia 1
• Maintain ECG monitoring for at least 3 days after successful cardioversion 4

Antiarrhythmic Support

• Administer antiarrhythmic medication if early relapse occurs or to prevent acute reinitiation 1, 3
• For atrial fibrillation: Consider amiodarone 150 mg IV over 10 minutes before repeated cardioversion attempts 3, 4
• For ventricular tachycardia: Amiodarone or procainamide may improve success rates 3, 4

If Initial Cardioversion Fails

• Adjust electrode position or apply more pressure over electrodes 3
• Administer antiarrhythmic medication before subsequent attempts 3
• Consider double-dose cardioversion using two defibrillators simultaneously in refractory cases (up to 720J total) 6

Special Considerations for Rheumatic Heart Disease with Atrial Fibrillation

• Electrical cardioversion is appropriate as part of a stepwise rhythm control strategy 7
• Patients with shorter duration of atrial fibrillation (<3 years) have better success rates for maintaining sinus rhythm 7
• Anticoagulation management follows standard atrial fibrillation guidelines regardless of rheumatic etiology 1

Critical Pitfalls to Avoid

• Never delay cardioversion in hemodynamically unstable patients while attempting pharmacological conversion 3, 4
• Do not use unsynchronized mode for organized rhythms (this is defibrillation, not cardioversion) - risk of inducing ventricular fibrillation 1
• Avoid cardioversion in patients with digitalis toxicity or uncorrected hypokalemia due to high risk of fatal arrhythmias 1, 3
• Do not perform frequent repeated cardioversions in patients who have only brief periods of sinus rhythm between relapses despite antiarrhythmic therapy 1