When is synchronized cardioversion (cardioversion using electrical shock synchronized with the patient's cardiac rhythm) recommended for patients with arrhythmias (irregular heart rhythms)?

From the Guidelines

Synchronized cardioversion is recommended for patients with hemodynamically unstable tachyarrhythmias, particularly atrial fibrillation, atrial flutter, and supraventricular tachycardia that have not responded to medication therapy, as well as for stable patients with these arrhythmias when medications have failed or are contraindicated. The procedure involves delivering an electrical shock timed with the R wave of the ECG to avoid the vulnerable period of the cardiac cycle, reducing the risk of inducing ventricular fibrillation.

Key Considerations

• For atrial fibrillation, initial energy levels typically start at 120-200 joules with biphasic defibrillators, while atrial flutter and SVT may respond to lower energies of 50-100 joules 1.
• Prior to elective cardioversion, patients should be anticoagulated for at least 3 weeks if the arrhythmia has persisted for more than 48 hours to prevent thromboembolism 1.
• The patient should fast for 6-8 hours before the procedure, and sedation with short-acting agents like midazolam (1-5 mg IV) or propofol (0.5-1 mg/kg IV) is administered.
• Synchronized cardioversion works by depolarizing all cardiac cells simultaneously, allowing the heart's natural pacemaker to regain control and restore normal rhythm, making it an effective treatment for tachyarrhythmias that compromise hemodynamic stability.

Specific Recommendations

• Synchronized cardioversion is highly effective in terminating AVRT, and when the patient is stable, this is performed after adequate sedation or anesthesia 1.
• Synchronized cardioversion should be performed for acute treatment in hemodynamically unstable patients with AVRT if vagal maneuvers or adenosine are ineffective or not feasible 1.
• Synchronized cardioversion is recommended for acute treatment in hemodynamically stable patients with AVRT when pharmacological therapy is ineffective or contraindicated 1.

From the Research

Synchronized Cardioversion Recommendations

Synchronized cardioversion is recommended for patients with arrhythmias in the following situations:

• Hemodynamically unstable patients with severely depressed cardiac output and recent-onset atrial fibrillation, where immediate electrical cardioversion is the treatment of choice 2
• Patients with supraventricular tachycardias, where synchronized cardioversion can be used to disrupt reentrant pathways 2
• Patients with atrial fibrillation or atrial flutter, where cardioversion is widely used to restore and maintain sinus rhythm 3, 4, 5

Patient Selection Criteria

The decision to perform synchronized cardioversion should be based on the following criteria:

• Patient's cardiac rhythm and hemodynamic stability 2
• Presence of atrial thrombi, which may require anticoagulation before cardioversion 2
• Patient's comorbidity profile and antiarrhythmic drug onset of action and side effect profile 4
• Need for a physician with experience in sedation or anaesthetics support for electrical cardioversion 4

Cardioversion Methods

The choice of cardioversion method depends on the patient's condition and the physician's preference:

• Electrical cardioversion, which is a widely used and effective method for termination of nonparoxysmal AF 5
• Pharmacological cardioversion, which is preferable in specific circumstances and can be used to restore and maintain sinus rhythm 4, 5
• Combination of electrical and pharmacological cardioversion, which may be used in some cases 4

Risks and Complications

Synchronized cardioversion is associated with risks and complications, including:

• Proarrhythmia, which can occur with both pharmacological and electrical cardioversion 5
• Stroke or systemic embolism, which can occur in patients with atrial fibrillation or atrial flutter 4, 6
• Mortality, which is extremely low but can occur in rare cases 4