Non-Shockable Rhythm in Cardiac Arrest

Introduction

When a person suffers a cardiac arrest, their heart may demonstrate different types of electrical activity. Some of these rhythms can be treated with a defibrillator shock (shockable rhythms), while others cannot (non-shockable rhythms). Understanding non-shockable rhythms is crucial as they require a different approach to resuscitation.

Types of Non-Shockable Rhythms

There are two main types of non-shockable rhythms: 1. Asystole (Flatline) – This is a complete absence of electrical activity in the heart. It appears as a straight line on an ECG. 2. Pulseless Electrical Activity (PEA) – This occurs when there are electrical signals in the heart, but they are ineffective in generating a pulse and blood circulation.

Causes of Non-Shockable Rhythms

Non-shockable rhythms often result from underlying conditions that prevent the heart from functioning effectively. Common reversible causes are summarized by the mnemonic H’s and T’s:

H’s (Hypoxia, Hypovolemia, Hydrogen ions, Hypo-/Hyperkalemia, Hypothermia)

• Hypoxia – Lack of oxygen to the heart and brain
• Hypovolemia – Severe blood or fluid loss
• Hydrogen ion (Acidosis) – An imbalance in blood acidity
• Hypo-/Hyperkalemia – Imbalance in potassium levels affecting the heart
• Hypothermia – Low body temperature leading to cardiac dysfunction

T’s (Tension Pneumothorax, Tamponade, Toxins, Thrombosis - Pulmonary or Coronary)

• Tension Pneumothorax – Air trapped in the chest cavity compressing the heart
• Tamponade (Cardiac) – Fluid buildup around the heart restricting function
• Toxins (Drug Overdose, Poisoning) – Certain substances can suppress heart activity
• Thrombosis (Pulmonary or Coronary) – Blood clots in the lungs (pulmonary embolism) or heart arteries (heart attack)

Management of Non-Shockable Rhythms

Since defibrillation is ineffective, focus is placed on: 1. High-Quality CPR (Cardiopulmonary Resuscitation) – To maintain blood flow to the brain and heart 2. Oxygenation and Airway Management – Ensuring proper breathing support 3. Identifying and Treating the Underlying Cause (H’s and T’s) 4. Administration of Epinephrine – To improve circulation and support heart rhythm

Prognosis and Importance of Early Intervention

The chances of survival depend on the speed and effectiveness of resuscitation. Early CPR, rapid identification of the cause, and advanced medical intervention are critical for successful outcomes.

Source recommendations

1. American Heart Association Guidelines for Cardiopulmonary Resuscitation (CPR) and Emergency Cardiovascular Care (ECC)

1. https://cpr.heart.org/en/resuscitation-science/cpr-and-ecc-guidelines
2. https://professional.heart.org/en/science-news/2020-aha-guidelines-for-cpr-and-ecc
3. https://cpr.heart.org/en/resources/about-cpr-and-ecc
4. https://professional.heart.org/en/science-news/2015-aha-guidelines-update-for-cpr-and-ecc-science
5. https://cpr.heart.org/-/media/cpr-files/cpr-guidelines-files/highlights/hghlghts_2020_ecc_guidelines_english.pdf

2. European Resuscitation Council Guidelines for Resuscitation

1. https://cprguidelines.eu/guidelines-2021
2. https://www.erc.edu/
3. https://cprguidelines.eu/
4. https://www.sciencedirect.com/science/article/pii/S0300957221000551
5. https://pubmed.ncbi.nlm.nih.gov/33773825/