Which heart rhythms can be treated with shock therapy, such as defibrillation or cardioversion?

From the Guidelines

Shock therapy, including defibrillation and cardioversion, is primarily used to treat tachyarrhythmias such as ventricular fibrillation, pulseless ventricular tachycardia, stable ventricular tachycardia, atrial fibrillation, atrial flutter, and supraventricular tachycardia that are unresponsive to medication. The following heart rhythms can be treated with shock therapy:

• Ventricular fibrillation
• Pulseless ventricular tachycardia
• Stable ventricular tachycardia
• Atrial fibrillation
• Atrial flutter
• Supraventricular tachycardia Defibrillation delivers a high-energy unsynchronized shock and is used in emergency situations for life-threatening arrhythmias like ventricular fibrillation and pulseless ventricular tachycardia 1. Cardioversion uses synchronized lower-energy shocks for stable arrhythmias like atrial fibrillation, atrial flutter, and stable ventricular tachycardia 1. Synchronization ensures the shock is delivered when the heart is not vulnerable to inducing ventricular fibrillation. Some key points to consider when using shock therapy include:
• The energy dose and timing of shocks for treatment of VT with pulses are determined by the patient’s condition and the morphological characteristics of the VT 1
• For cardioversion, patients typically need to be anticoagulated if the arrhythmia has been present for more than 48 hours, and they should fast for 6-8 hours before the procedure
• Shock therapy works by depolarizing all cardiac cells simultaneously, allowing the heart's natural pacemaker to regain control and restore normal rhythm It's also important to note that bradyarrhythmias and asystole (flatline) do not respond to shock therapy and require different interventions 1. The most recent and highest quality study on this topic is from 2015, which provides guidance on the use of anti-arrhythmic drugs in acute coronary syndromes and the prevention of sudden cardiac death 1.

From the FDA Drug Label

Amiodarone HCl injection is indicated for initiation of treatment and prophylaxis of frequently recurring ventricular fibrillation (VF) and hemodynamically unstable ventricular tachycardia (VT) in patients refractory to other therapy

The heart rhythms that can be treated with shock therapy, such as defibrillation or cardioversion, are:

• Ventricular Fibrillation (VF)
• Hemodynamically unstable Ventricular Tachycardia (VT) 2

From the Research

Heart Rhythms That Can Be Shocked

The following heart rhythms can be treated with shock therapy, such as defibrillation or cardioversion:

• Ventricular tachycardia (VT) 3, 4, 5, 6, 7
• Ventricular fibrillation (VF) 3, 4, 5, 6, 7
• Pulseless ventricular tachycardia (VT) 5, 6

Specific Types of Ventricular Tachycardia

Different types of VT can be shocked, including:

• Monomorphic VT (MVT) 4
• Polymorphic VT (PVT) 4
• Symptomatic VT with a palpable pulse 3
• Pulseless VT 5, 6

Energy and Current Requirements

The energy and current requirements for shocking different heart rhythms vary:

• MVT requires relatively low current or energy 4
• PVT requires higher electrical current or energy 4
• VF requires higher energy doses than VT 4, 5
• Pediatric VF and pulseless VT require initial biphasic direct current shock doses of 2-5 J/kg 5

Treatment Outcomes

The outcomes of shock therapy for different heart rhythms are:

• Defibrillation shocks delivered shortly after the peak of the QRS complex in rapid VT have a success rate of 93% 3
• Immediate defibrillation results in significantly higher levels of immediate return of spontaneous circulation (ROSC) than precordial thump 6
• Multiple shocks do not favor ROSC 5, 6