Shockable Heart Rhythms
A common question we get asked is “What heart rhythms does an AED shock?”. When a heart stops beating effectively during cardiac arrest, the type of rhythm it’s experiencing can influence the emergency response. There is a need to distinguish between non-shockable and shockable heart rhythms–especially in the context of using an AED.
Understanding Heart Rhythms
Heart rhythms refer to our heartbeat patterns. They can vary from healthy and regular to erratic and life-threatening. These patterns are governed by the heart’s electrical system, a sophisticated network that coordinates the heartbeat through electrical signals. When these signals operate correctly, they ensure the heart beats in a rhythm that pumps blood efficiently throughout the body.
When these electrical impulses are disrupted, the heart’s rhythm can change dramatically and lead to conditions that require immediate attention. This disruption can result in either non-shockable or shockable heart rhythms.
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Shockable Heart Rhythm
Shockable heart rhythms occur when the heart’s electrical activity becomes chaotic and prevents the heart from pumping blood effectively. They are deemed “shockable heart rhythms” because they can potentially be corrected through an electrical shock from an AED. These shockable heart rhythms primarily include ventricular fibrillation (VF) and ventricular tachycardia (VT) without a pulse.
Ventricular Fibrillation (VF)
Ventricular fibrillation is characterized by a rapid, erratic heartbeat that prevents the heart from pumping blood, which leads to immediate collapse and death if not treated quickly. VF is the most common arrhythmia in cases of sudden cardiac arrest and is directly treatable with an AED.
Pulseless Ventricular Tachycardia (VT)
Ventricular tachycardia (when pulseless) is a condition where the heart beats faster than normal, but in a regular pattern. Like VF, VT without a pulse is a critical condition that requires immediate intervention with an AED.
Here’s a shocking stat–in more than 80% of deaths caused by sudden cardiac arrest, the patient’s heart rhythm was shockable. In other words, the patient could have survived if an AED had been used.
Non-Shockable Heart Rhythm
Non-shockable rhythms mean the heart’s electrical system is either too weak to initiate a beat or is failing to produce a heartbeat despite electrical activity. While shockable heart rhythms like VF and pulseless VT can be effectively treated with an AED, not all cardiac emergencies involve rhythms that respond to defibrillation. Non-shockable heart rhythms present unique challenges in emergency cardiac care and require a different approach to treatment.
Asystole
Commonly known as “flatline”, asystole is a condition where the heart ceases to produce any electrical activity. It means there is an absence of both heart rhythm and pulse. Unlike VF or VT, asystole cannot be treated with a shock.
The primary approach to managing asystole involves high-quality CPR and medications. Though the outcome of asystole depends on many factors, the prognosis is poor–data suggests that less than 2% of patients with asystole survive.
Pulseless Electrical Activity
Pulseless electrical activity (PEA) is a condition where electrical activity is observed on the heart monitor, but there is no effective heartbeat or pulse detectable. Because the heart’s electrical activity does not translate into the mechanical action of pumping blood, defibrillation is rendered ineffective.
Similar to asystole, treatment for PEA focuses on performing continuous, high-quality CPR and administering appropriate medications.
How AEDs Analyze & Shock
AEDs are specifically designed to diagnose shockable heart rhythms through their built-in analysis software. Upon attaching the AED pads to a person’s chest, the device immediately begins to measure the heart’s electrical activity to determine whether a shock is appropriate. If the device detects a shockable rhythm, it will let the rescuer know that it’s charging. During this time, the machine is building up an electromagnetic charge that the rescuer will then administer as a shock.
Once charged, the AED uses audio cues to instruct the rescuer to stay clear of the patient and administer the shock. The shock then travels from the device and through the pads into the patient. The electric current of an AED shock is precisely measured at typically:
- 150 joules for an adult
- 50 joules for a child
AEDs are designed with safety in mind and will only advise administering a shock if it detects a rhythm that can be treated by defibrillation. If a non-shockable rhythm is detected, or if no rhythm is detected at all, the AED will not permit a shock to be delivered. Instead, it will instruct the rescuer to continue CPR until professional medical help arrives.
The simplicity and intelligence of AEDs make them invaluable tools in public spaces, workplaces, and homes. Their ability to guide even untrained rescuers through the process of assessing and responding to sudden cardiac arrest situations significantly increases the chances of survival for victims of shockable heart rhythms.
Here are 10 reasons why we need more AEDs in public spaces.
As you can see, not all cardiac emergencies are the same. There are vital differences between non-shockable and shockable heart rhythms and the response must be tailored to the emergency.
As we come to a close on understanding heart rhythms and the role of AEDs, we encourage you to equip yourself with the knowledge required to take swift action in a sudden cardiac emergency.
Together, we can make a difference in the crucial moments that matter most.
Making a real difference starts with getting an AED and becoming first aid certified. Order an Onsite AED and register for a CPR/AED first aid course today.
