From the Guidelines
Cardioversion of polymorphic wide complex tachycardia should be performed immediately with an unsynchronized shock at 200 joules (biphasic) or 360 joules (monophasic). This approach is based on the most recent and highest quality evidence, which emphasizes the importance of rapid defibrillation in unstable patients with wide-complex tachycardia 1. The patient should be sedated if conscious and time permits, but treatment should not be delayed in unstable patients.
Key Considerations
- The patient's condition should be evaluated to determine if they are stable or unstable, and immediate cardioversion should be performed if they are unstable 1.
- Unsynchronized shocks are preferred for polymorphic tachycardias because the varying QRS morphology makes it difficult for the defibrillator to synchronize effectively, and attempting synchronization would dangerously delay the necessary shock delivery in this rapidly deteriorating condition.
- After successful cardioversion, immediate attention should be given to identifying and treating the underlying cause, which may include electrolyte abnormalities (particularly potassium, magnesium), ischemia, drug toxicity, or congenital conditions.
Treatment Options
- Amiodarone 150 mg IV over 10 minutes followed by an infusion may be considered to prevent recurrence 1.
- Magnesium sulfate 2g IV is often beneficial, especially if torsades de pointes is suspected.
- Procainamide or flecainide may be considered for patients with hemodynamically stable monomorphic VT who do not have severe congestive heart failure or acute myocardial infarction 1.
Clinical Decision-Making
- The choice of treatment depends on the stability of the patient and the rhythm, with electric cardioversion being the preferred option for hemodynamically unstable patients 1.
- Expert consultation should be considered when treating wide-complex tachycardias, especially if the patient's condition is unstable or the rhythm is irregular 1.
From the Research
Approach to Cardioversion of Polymorphic Wide Complex Tachycardia (Ventricular Tachycardia)
The approach to cardioversion of polymorphic wide complex tachycardia, also known as ventricular tachycardia (VT), depends on the patient's hemodynamic stability.
- For unstable patients, immediate cardioversion is required 2, 3, 4.
- For stable patients, the initial approach includes the use of lidocaine or procainamide 2, 5.
- Adenosine may be used as a diagnostic aid to identify the dysrhythmia, but its use as a treatment is generally reserved for wide QRS supraventricular tachycardia (SVT) 2, 6.
- Magnesium sulfate may be useful in refractory cases of VT and torsades de pointes 2.
Key Considerations
- The history, physical examination, and ECG provide essential information for diagnosing wide complex tachycardias 2, 6.
- ECG analysis is crucial in differentiating VT from SVT, with characteristics such as AV dissociation, QRS duration, and QRS axis being important indicators 2.
- A four-step approach to ECG analysis has been reported to accurately identify patients with VT, but prospective validation in an emergency department setting is lacking 2.
- Direct current cardioversion is the most efficacious treatment for stable monomorphic VT, with procainamide being the most effective medical management option 5.