From the Guidelines
Cardioversion is most suitable for treating atrial fibrillation, atrial flutter, paroxysmal supraventricular tachycardia (PSVT), and ventricular tachycardia with a pulse, as these arrhythmias can be effectively converted to a normal sinus rhythm with minimal risk of complications 1. The procedure involves delivering a synchronized electrical shock to the heart, usually starting at 120-200 joules for biphasic defibrillators for atrial fibrillation, 50-100 joules for atrial flutter, and 100 joules for PSVT. For ventricular tachycardia, higher energies of 200 joules or more may be needed. Sedation with short-acting agents like midazolam (1-2mg IV) and fentanyl (50-100mcg IV) is typically administered before the procedure. It's essential to note that cardioversion is contraindicated in cases of digitalis toxicity, as resulting ventricular tachyarrhythmia may be difficult to terminate 1. Additionally, serum potassium levels should be in the normal range for safe, effective cardioversion, and magnesium supplementation does not enhance cardioversion 1. The risks of direct-current cardioversion are mainly related to thromboembolism and arrhythmias, and prophylactic antithrombotic therapy is discussed in the guidelines 1, 2. Some key points to consider when evaluating a patient for cardioversion include:
- The presence of underlying sinus node dysfunction, which may be unmasked after cardioversion
- The need for anticoagulation therapy before cardioversion to prevent thromboembolism
- The importance of excluding clinical and ECG signs of digitalis excess before proceeding with cardioversion
- The potential for benign arrhythmias, such as ventricular and supraventricular premature beats, to arise after cardioversion and commonly subside spontaneously. Overall, cardioversion can be an effective treatment option for certain arrhythmias, but it's crucial to carefully evaluate each patient and follow established guidelines to minimize risks and ensure the best possible outcome 1.
From the FDA Drug Label
Ibutilide fumarate injection is indicated for the rapid conversion of atrial fibrillation or atrial flutter of recent onset to sinus rhythm. Patients with atrial arrhythmias of longer duration are less likely to respond to ibutilide fumarate injection. The effectiveness of ibutilide has not been determined in patients with arrhythmias of more than 90 days in duration. Among patients with atrial flutter, 53% receiving 1 mg ibutilide fumarate and 70% receiving 2 mg ibutilide fumarate converted, compared to 18% of those receiving sotalol In patients with atrial fibrillation, 22% receiving 1 mg ibutilide fumarate and 43% receiving 2 mg ibutilide fumarate converted compared to 10% of patients receiving sotalol.
The arrhythmias suitable for cardioversion are:
- Atrial fibrillation of recent onset
- Atrial flutter of recent onset These arrhythmias are likely to respond to cardioversion if they are of recent onset, typically less than 90 days in duration 3, 4.
From the Research
Suitable Arrhythmias for Cardioversion
The following arrhythmias are suitable for cardioversion:
- Atrial fibrillation (AF) 5, 6, 7, 8, 9
- Atrial flutter 7, 8
- AV-nodal reentry tachycardia with rapid ventricular response 7
- Atrial ectopic tachycardia 7
- Preexcitation syndromes combined with atrial fibrillation or ventricular tachyarrhythmias 7
- Ventricular tachyarrhythmias 7
Considerations for Cardioversion
When considering cardioversion, the following factors should be taken into account:
- Duration of the arrhythmia: cardioversion is more effective for recent-onset arrhythmias 6, 8, 9
- Hemodynamic stability: electrical cardioversion is usually reserved for hemodynamically unstable patients, while pharmacological cardioversion is preferred for hemodynamically stable patients 9
- Anticoagulation: cardioversion should be carried out under effective therapeutic anticoagulation to reduce the risk of thromboembolic complications 6
- Risk of stroke: the decision to continue anticoagulation after cardioversion should be based on the risk of stroke, as assessed with the CHA2DS2-VASc score 6