Automated External Defibrillators (AEDs) are portable medical devices that deliver an electrical shock to the heart. They are used in emergency situations, particularly during sudden cardiac arrest, to help restore a normal heart rhythm. This intervention can be performed by trained bystanders.
Understanding Sudden Cardiac Arrest
Sudden Cardiac Arrest (SCA) occurs when the heart unexpectedly stops beating effectively, leading to an immediate loss of consciousness, breathing, and pulse. This condition results from an electrical malfunction within the heart, causing it to quiver instead of pumping blood. If not addressed within minutes, SCA can quickly lead to brain damage and death because blood circulation to the brain and other vital organs ceases.
SCA is distinct from a heart attack, which is a circulation problem where blood flow to the heart is blocked. While a heart attack involves a blockage, SCA is an electrical issue where the heart’s electrical activity becomes disorganized. A heart attack can sometimes increase the risk of SCA, but they are not the same event. Immediate action is important for SCA, as every minute without intervention significantly reduces the chance of survival.
How Automated External Defibrillators Work
An Automated External Defibrillator (AED) is a compact, electronic device specifically engineered for use by laypersons, even with minimal training. When applied, electrode pads are placed on the person’s bare chest, allowing the AED to analyze the heart’s electrical rhythm. The device’s internal computer determines if the rhythm can benefit from an electrical shock, such as ventricular fibrillation.
If a shockable rhythm is detected, the AED charges itself and, depending on the model, either automatically delivers the shock or prompts the user to press a button. This controlled electrical shock aims to depolarize the heart muscles, effectively resetting the heart’s electrical activity, allowing its natural pacemaker to re-establish a normal rhythm. AEDs are designed with voice prompts and visual cues to guide the rescuer step-by-step through the process, making them user-friendly.
The Impact of AEDs on Survival Rates
The use of an AED significantly increases the chance of survival from sudden cardiac arrest, especially when deployed rapidly. When an AED delivers a shock within the first few minutes of SCA, survival rates can dramatically improve. For instance, in cases where ventricular fibrillation is the cause, survival rates can be as high as 74% if the first shock is delivered within three minutes of collapse. This contrasts with survival rates of about 7% for cardiac arrest victims who receive no bystander CPR or defibrillation.
Time is a critical factor. The chance of survival from SCA decreases by approximately 7% to 10% for every minute that passes without defibrillation. This emphasizes why immediate access to an AED and prompt use are important. Public access defibrillation (PAD) programs, which place AEDs in community settings, have shown survival rates ranging from 50% to 70%.
Bystander cardiopulmonary resuscitation (CPR) also plays a role in improving survival when combined with AED use. While CPR manually circulates blood to the brain and organs, it does not restart the heart; only defibrillation can do that. Immediate CPR can significantly increase the chances of survival and positive neurological outcomes, even before an AED is available.
In observed out-of-hospital cardiac arrests, survival to hospital discharge was 38% when both bystander CPR and an AED shock were provided before emergency medical services arrived. This highlights the combined power of these interventions. Increased use of AEDs in public settings has been associated with a rise in neurologically favorable survival outcomes.
Maximizing Survival: The Chain of Survival
Automated External Defibrillators are powerful tools in combating sudden cardiac arrest, representing one crucial link within the Chain of Survival. This concept outlines a series of coordinated actions that maximize the chances of survival from SCA.
The chain begins with early recognition of cardiac arrest and immediate activation of the emergency response system, such as calling 911. The second link involves early cardiopulmonary resuscitation (CPR), focusing on chest compressions to maintain blood flow to the brain and other vital organs until defibrillation or advanced care can be provided.
The third link is rapid defibrillation, where the AED is indispensable. Delivering an electrical shock as soon as possible addresses the underlying electrical problem in many SCA cases. Following these bystander actions, the chain continues with early advanced life support provided by emergency medical services. The final links involve integrated post-cardiac arrest care in a hospital setting and a focus on recovery, including rehabilitation and psychological support for survivors.