Can A Defibrillator Kill You?

In this article, we will take a close look at the role of a defibrillator in treating life-threatening cardiac dysrhythmias. We will explore whether a defibrillator can cause death. We will describe the function, use, and energy of defibrillation. This comprehensive guide will provide insights into the medical and basic technical aspects of defibrillators.
Jakub Gwiazdecki

Jakub Gwiazdecki

Fifth year medical student at the Medical Faculty of Comenius University in Bratislava.

A blue image with text saying "Can A Defibrillator Kill You?"

Can A Defibrillator Kill You?

The short answer is no. A defibrillator cannot directly cause death. It's quite the opposite. Defibrillators are designed to prevent sudden cardiac death (SCD). Even in an older review by J Neuzner et al., it is pointed out that defibrillation has a positive impact on high-risk patients. The mortality due to SCD is lower than 2% thanks to the defibrillators [1, 2].

However, in some cases, defibrillators have been associated with an increased risk of death. Typically, it is linked to some underlying health conditions or complications. For example, there is a strong association between shocks from implantable cardioverter defibrillators (ICDs). In patients with this devise, an increased mortality was noticed. However, it is far from clear whether the shocks, the placement or the presence of the device are contributors to this association [3].

Even with some doubts the answer to the main question remains no, a defibrillator itself cannot kill you. It is a device designed to save lives not to take them.

What is a defibrillator?

A defibrillator is a medical device designed to restore a normal heart action. It is made of a central battery with a command computer and pads connected to the battery. Via those pads, the defibrillator delivers a shock of electricity to the tissues. This device is crucial in situations when the heart stops pumping blood and the cardiac muscle shivers. The electric current sent through the body is a form of reset for the lost heart. There are several types of defibrillators, including implantable cardioverter defibrillator (ICD), wearable cardioverter defibrillator (WCD), and automated external defibrillator (AED) [4]. All types differ in size and use. Some of them are used in patients with chronic heart problems, others are used as rescue in acute situations.

What is a defibrillator used for?

A defibrillator is often used to prevent or correct life-threatening arrhythmias. Those are conditions where the heart can beat too fast, too slowly, or at an irregular rhythm. In all those situations the blood flow is compromised. If not helped promptly those rhythms can end with death. Most of the people saw in films or perhaps in real life a defibrillator. In Europe, defibrillators are found on some streets of major cities. Those are the automated external defibrillators. They are used in acute situations and thanks to their proximity they can help very effectively in many situations. In the hospitals, patients with a high risk of sudden cardiac death are recommended for implantation of an automated defibrillator. This machine is a small device put in the chest. It has a huge advantage of monitoring the heart’s action. Owing to this monitoring it is very effective as it fires nearly the moment it reads a dangerous rhythm. The shock it produces is not a big full body shock. This is a small heart-focused shock[4].

When is a defibrillator used?

A defibrillator is used in cases of cardiac emergencies. It saves lives during sudden cardiac arrest, a condition that can lead to death within minutes if not treated quickly [5]. One of the most common causes of cardiac arrest is ventricular fibrillation. This is a pathological situation in the ventricles of the heart. From its onset the chamber loses its ability to contract, thus the blood is not being pumped out of the heart. Luckily it can be successfully treated by the electric countershock. In situations like this key is the quick reaction [6, 7]. A similar situation is with Ventricular Tachycardia. Here the heart beats extremely fast so that nearly no blood can fill and leave the ventricle. Also, this rhythm is treated with a shock. In other conditions, like systole (nor heart activity at all) or atrial fibrillations, the defibrillations are not effective. Thus in those situations other treatment has to be given often in the hospital.

How to know what rhythm a fainting individual on the street has? The modern automated external defibrillators (AEDs) are designed to diagnose the patient's cardiac rhythm. Even more, they are able to make a decision about defibrillation without our help [8]. All this is thanks to special algorithms that analyse the patient's electrocardiogram (ECG) after the electrode placement [9]. After the analysis is done, the device informs out load whether to shock or not.

How does a defibrillator work?

A defibrillator works by detecting the heart's rhythm. In an ICD, a generator containing a battery and circuitry is attached to wired sensors. These sensors rest on or inside your heart and help the ICD determine the intensity of the shock to deliver. A low-energy shock can speed up or slow down your heart rate. In some situations, a high-energy shock is needed, such as when the heart is beating very quickly or irregularly, or the ventricles begin to fibrillate (quiver). Defibrillators like ICDs and WCDs can also record your heart rhythms, which can help your doctor understand how well your defibrillator is working to help prevent potentially dangerous arrhythmias [4].

Rescue Algorithms

When talking about defibrillation it is important to point out that there are special guidelines/ rescue algorithms. In them is it described how and when to use the defibrillators to optimize the timing and maximize the shock success [10].

A key aspect of these algorithms is the detection of cardiac arrest. When a defibrillator is attached to the patient an algorithm based on the impedance cardiogram (ICG) recorded through the two defibrillation pads determines circulatory arrest [11]. However, the basic step can be performed manually by physical examination of an unresponsive individual.

In addition to rhythm analysis, the rescue algorithms also involve the delivery of defibrillation shocks. The American Heart Association recommends single defibrillation shocks with immediate provision of cardiopulmonary resuscitation and minimal interruptions in chest compressions [12].

The energy of the defibrillation

The energy of a defibrillator during a cardiac event can influence the success rate of the defibrillation. When the electric current is too low the heart may not react to the stimulus. The energy required for successful defibrillation varies and is influenced by several factors. Those factors include the specific condition of the patient's heart and the duration of the cardiac arrest.

In general, the energy level for biphasic defibrillation of ventricular fibrillation is 150 J. Form there the energy can be step-wise increased to 360 J [13]. In most cases, 200 J is sufficient to reset the heart [14]. This amount of energy is needed as the electric current has to go through the whole body. However, the energy requirement can be lower in some cases.

There are also patients who require higher energy levels. For example, a study by P Ouyang et al. found that out of 233 episodes, 222 (95%) were converted by 200 J shocks [15]. Another study by J P Morgan et al. recommended that 400 J of delivered energy be used initially for the first shocks administered [16].

The energy delivered by a defibrillator should be tailored to the individual patient's needs. Taking into account body mass, heart condition and the duration of the cardiac arrest. It's important to note that while higher energy levels may increase the success rate of defibrillation, they also result in greater energy consumption and potential loss in energy efficiency. On the other hand, in life-threatening situations the small adjusting of the energy may be a simple loss of time. The energy adjustment has to be quick but be performed with reason and expertise.

Jakub Gwiazdecki

Jakub Gwiazdecki

Jakub is in his fifth year as a medical student at Comenius University in Bratislava, Slovakia. He has special interested in cardiology and in patient-centered medicine. His love for heart health isn't just book-smarts; he wants to know how it works, what it means for our feelings, and how key it is for health and happiness. Jakub thinks real good health care comes from always putting the patient at the centre, treating each person as a whole.