Arrhythmias and Cardiac Arrest Overview

Arrhythmias and Cardiac Arrest

Arrhythmias are abnormal rhythms of the heart and are a common cause of sudden cardiac arrest. Cardiac arrest occurs when the heart stops beating due to an irregular heart rhythm, leading to the sudden loss of blood flow and oxygen to the body. Arrhythmias can be broadly categorized into two types: tachyarrhythmias and bradyarrhythmias. Tachyarrhythmias include ventricular fibrillation (VF) and pulseless ventricular tachycardia (VT), while bradyarrhythmias include pulseless electrical activity (PEA) and asystole.

Tachyarrhythmias

Ventricular Fibrillation (VF)

VF is an irregular and rapid heart rhythm that involves the lower chambers of the heart (ventricles). It is characterized by rapid, disorganized electrical activity that prevents the heart from pumping blood effectively. VF is a life-threatening condition that requires immediate medical attention.

Pulseless Ventricular Tachycardia (VT)

VT is a rapid heart rhythm that originates from the ventricles and can result in a loss of consciousness and cardiac arrest. Unlike VF, which is characterized by an irregular and chaotic electrical pattern, VT is more predictable and can sometimes be treated with defibrillation.

Bradyarrhythmias

Pulseless Electrical Activity (PEA)

PEA is a condition where the heart produces electrical activity but is unable to pump blood effectively. It is often caused by conditions such as severe hypovolemia, tension pneumothorax, pulmonary embolism, or cardiac tamponade. PEA is a non-shockable rhythm, meaning that it does not respond to defibrillation.

Asystole

Asystole is the absence of any electrical activity in the heart. It is a life-threatening condition that requires immediate medical attention, as it indicates that the heart has stopped functioning.

Arrhythmias During Cardiac Arrest

During cardiac arrest, the heart may exhibit arrhythmias that can affect the patient's chances of survival. The initial rhythm recorded on an ECG is an indicator of the underlying etiology, duration of cardiac arrest, quality of CPR, and a prognostic indicator for survival. For example, victims of out-of-hospital cardiac arrest (OHCA) have a 35% chance of survival if they have a shockable rhythm (VF or pulseless VT), while victims with asystole have a 1.6% chance of survival.

ECG and PoCUS During Cardiopulmonary Resuscitation

ECG rhythms are used during advanced cardiac life support (ACLS) to guide resuscitation management. While ECG rhythms can provide valuable information, there is some evidence to suggest that they may not accurately predict ongoing mechanical cardiac activity, particularly in non-shockable cases. Point-of-care ultrasound (PoCUS) has emerged as a valuable tool in identifying patients with ongoing mechanical cardiac activity during cardiac arrest. By combining ECG and PoCUS, medical professionals can make more informed decisions about the appropriate resuscitative pathway for each patient.