What are shockable rhythms, specifically ventricular fibrillation (VF) and pulseless ventricular tachycardia (VT)?

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From the Guidelines

Shockable rhythms are ventricular fibrillation (VF) and pulseless ventricular tachycardia (pVT), which can be treated with electrical defibrillation during cardiac arrest. The primary treatment for these rhythms is immediate defibrillation, with the goal of restoring a perfusing cardiac rhythm. According to the most recent guidelines 1, for adult patients, defibrillation should be performed using 120-200 joules with a biphasic defibrillator or 360 joules with a monophasic defibrillator.

Some key points to consider when treating shockable rhythms include:

  • The use of biphasic defibrillators, which have a high first-shock efficacy, averaging more than 90% 1
  • The importance of immediate CPR after defibrillation, with a focus on effective chest compressions 1
  • The recommendation to resume CPR immediately after attempted defibrillation, without interrupting chest compressions to check circulation 1
  • The use of medications like epinephrine and amiodarone or lidocaine during resuscitation, although the specific dosing and administration may vary depending on the patient's condition and the treating physician's discretion

It's also important to note that the energy levels for defibrillation may vary depending on the specific device being used, and healthcare providers should be aware of the range of energy levels for the device they are operating 1. Additionally, the use of automated external defibrillators (AEDs) can help simplify the defibrillation process and improve outcomes, but it's essential to follow the manufacturer's guidelines and recommendations for use 1.

In terms of the specific energy levels for defibrillation, the guidelines recommend using 150 J to 200 J for the initial shock with a biphasic truncated exponential waveform or 120 J with a rectilinear biphasic waveform 1. For children, the recommended initial dose is 2 J/kg (monophasic or biphasic), with subsequent biphasic shocks using the same or higher energy (2 to 4 J/kg) 1.

Overall, the key to successful treatment of shockable rhythms is early recognition and prompt defibrillation, followed by immediate CPR and ongoing resuscitation efforts as needed.

From the FDA Drug Label

Amiodarone hydrochloride injection is an antiarrhythmic agent 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 shockable rhythms are:

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

From the Research

Definition of Shockable Rhythms

  • Shockable rhythms refer to abnormal heart rhythms that can be treated with defibrillation, a medical intervention that uses electrical shocks to restore a normal heartbeat.
  • These rhythms include ventricular fibrillation (VF) and pulseless ventricular tachycardia (VT) 3.

Characteristics of Shockable Rhythms

  • Shockable rhythms are typically associated with cardiac arrest and require immediate medical attention.
  • They are often caused by underlying heart conditions, such as ischemic heart disease, and can be treated with medications like epinephrine and antiarrhythmics 4, 5.
  • The incidence of shockable rhythms, particularly VF, has been declining in recent years due to improved medical and surgical therapies, as well as the use of implantable cardiac defibrillators (ICDs) 3.

Treatment of Shockable Rhythms

  • Defibrillation is the primary treatment for shockable rhythms, and is often performed in conjunction with cardiopulmonary resuscitation (CPR) 4, 5.
  • Medications like epinephrine and antiarrhythmics may also be used to treat shockable rhythms, particularly if initial defibrillation attempts are unsuccessful 4, 5.
  • The use of antiarrhythmic drugs, such as amiodarone and lidocaine, has been shown to be effective in treating refractory VF/VT, but the optimal treatment strategy is still uncertain 5.

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

Cardiac arrest: the changing incidence of ventricular fibrillation.

Current treatment options in cardiovascular medicine, 2015

Research

Emergency medicine updates: Cardiac arrest medications.

The American journal of emergency medicine, 2025

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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