An Automated External Defibrillator (AED) is a portable medical device designed to assist individuals experiencing sudden cardiac arrest. It analyzes heart rhythms and, when necessary, delivers an electrical shock. This shock addresses disruptions in the heart’s electrical activity, aiming to restore a normal rhythm and potentially save a life.
When the Heart’s Rhythm Goes Wrong
The heart functions through a precise electrical system that coordinates its chambers to pump blood efficiently throughout the body. Electrical impulses originate in the heart’s natural pacemaker and spread, causing the heart muscle to contract in an organized manner.
During sudden cardiac arrest, this organized electrical activity abruptly becomes chaotic and disorganized. Two common life-threatening rhythms are ventricular fibrillation (VF) and pulseless ventricular tachycardia (VT). In ventricular fibrillation, the heart’s lower chambers, the ventricles, quiver uselessly instead of pumping blood effectively. Pulseless ventricular tachycardia involves the ventricles beating extremely fast, but too inefficiently to produce a detectable pulse or circulate blood. In these situations, the heart is not truly “stopped” but is rather ineffectively quivering, unable to supply vital organs with blood.
How the Shock Resets the Heart
The purpose of an AED’s electrical shock is not to “jumpstart” a heart that has ceased all electrical activity, but to interrupt chaotic electrical signals. This “resets” the heart’s electrical system, similar to restarting a computer. The shock delivers a controlled electrical current that momentarily stuns all heart muscle cells simultaneously. This brief period of electrical silence allows the heart’s natural pacemaker to regain control and re-establish a normal, organized rhythm, enabling effective blood pumping.
How an AED Knows When to Deliver a Shock
Automated External Defibrillators are equipped with advanced analytical capabilities. Once electrode pads are placed on the patient’s chest, the AED analyzes the heart’s electrical rhythm. The device determines if a shockable rhythm, such as ventricular fibrillation or pulseless ventricular tachycardia, is present.
An AED will only advise and deliver a shock if it detects one of these specific life-threatening rhythms. This built-in safety mechanism prevents accidental shocks to individuals who do not require defibrillation. The device provides clear voice and visual prompts, ensuring a shock is administered only when medically appropriate.
The Goal of the Shock
The primary goal of the electrical shock delivered by an AED is to allow the heart’s inherent electrical system to resume a normal, effective pumping rhythm. This return to an organized rhythm enables the heart to circulate oxygenated blood throughout the body. Defibrillation is a time-sensitive intervention, as the chances of survival decrease significantly with each passing minute without treatment.
While the shock is a direct treatment for the electrical chaos, it is part of a broader resuscitation effort. High-quality cardiopulmonary resuscitation (CPR) is important before and after a shock. CPR helps maintain blood flow to the brain and other vital organs until a normal heart rhythm is restored or advanced medical help arrives.