What is a defibrillator?
A defibrillator is a device that delivers an electrical shock to the heart to restore a normal rhythm. It is primarily used to treat life-threatening arrhythmias, such as ventricular fibrillation (VF) and ventricular tachycardia (VT), which cause ineffective heart contractions. Defibrillators use electrocardiogram (ECG) leads and adhesive electrode pads (or paddles) to assess and correct abnormal heart rhythms.
The history of defibrillation
- 1899: Jean-Louis Prévost and Frédéric Batelli (University of Geneva) discovered that small electric shocks could induce ventricular fibrillation in animals and that larger shocks could reverse it.
- 1933: Dr. Albert Hyman developed an early prototype of a defibrillator to restore heart function, though its effectiveness was limited.
- 1947: Dr. Claude Beck performed the first successful human defibrillation during open-heart surgery using internal paddles.
- 1956: Paul Zoll developed an external defibrillator, paving the way for closed-chest defibrillation.
- 1959: Dr. V. Eskin and A. K. Klimov invented the first portable closed-chest defibrillator, requiring higher voltage.
- 1960s: Bernard Lown introduced the direct current (DC) defibrillator, replacing alternating current (AC) models.
- 1965: Professor Frank Pantridge developed the first portable defibrillator, enabling out-of-hospital resuscitation.
- 1980: Dr. Michel Mirowski and Dr. Levi Watkins performed the first successful implantation of an implantable cardioverter-defibrillator (ICD) at Johns Hopkins Hospital.
- 1990s: The biphasic truncated exponential (BTE) waveform replaced earlier defibrillation waveforms, improving success rates and reducing required energy levels.
Types of defibrillators
- Manual External Defibrillator (MED) – Used by trained professionals, requiring ECG interpretation and manual shock adjustment. Found in hospitals and advanced life support ambulances. (Neumar et al., 2015)
- Manual Internal Defibrillator (MID) – Uses internal paddles to directly apply shocks to the heart, primarily during open-heart surgery. (Zoll, 1956)
- Automated External Defibrillator (AED) – A portable, easy-to-use device with voice and visual instructions for bystanders. Found in public spaces (airports, schools, offices). (Link et al., 2015)
- Implantable Cardioverter-Defibrillator (ICD) – Continuously monitors heart rhythms and delivers shocks when needed. Used for patients at high risk of sudden cardiac arrest. (Mirowski et al., 1980)
- Wearable Cardiac Defibrillator (WCD) – A temporary, external device for patients at transient risk of cardiac arrest. Provides 24/7 monitoring but must be worn consistently. (Epstein et al., 2013)
When to use a defibrillator
Defibrillation is required in cases of ventricular fibrillation (VF) and pulseless ventricular tachycardia (pVT), which are both shockable rhythms.
VF occurs when the heart’s electrical activity becomes chaotic, preventing effective blood circulation.
Pulseless VT is a rapid, ineffective heart rhythm that can quickly deteriorate into VF.
In these situations, immediate defibrillation, combined with high-quality cardiopulmonary resuscitation (CPR), significantly improves survival rates. Defibrillation should be performed as soon as possible when these arrhythmias are detected, following Advanced Cardiac Life Support (ACLS) guidelines.
When not to use a defibrillator
Defibrillation is not appropriate in the following cases:
- Asystole (Flatline): No electrical activity; requires CPR and epinephrine instead. (Neumar et al., 2015)
- Pulseless Electrical Activity (PEA): Electrical activity present but no pulse; treated with CPR and medications. (Link et al., 2015)
- Conscious or Pulsed Patients: Unnecessary shocks may cause dangerous arrhythmias.
Conclusion
Defibrillators have transformed cardiac emergency care, significantly improving survival rates. With automated external defibrillators (AEDs) becoming widespread, even non-medical personnel can intervene in life-threatening situations. Continued advancements in ICDs and wearable technology further enhance cardiac care, making timely intervention more accessible than ever.
Resources
- Furman S. (2002). Early history of cardiac pacing and defibrillation. Indian pacing and electrophysiology journal, 2(1), 2–3.https://pmc.ncbi.nlm.nih.gov/articles/PMC1569902/
- U.S. Department of Health and Human Services. (n.d.). What are defibrillators?. National Heart Lung and Blood Institute. https://www.nhlbi.nih.gov/health/defibrillators
- Center for Devices and Radiological Health. (n.d.). Automated External Defibrillators (aeds). U.S. Food and Drug Administration. https://www.fda.gov/medical-devices/cardiovascular-devices/automated-external-defibrillators-aeds
- Mayo Foundation for Medical Education and Research. (2023, August 15). Implantable cardioverter-defibrillators (ICDS). Mayo Clinic. https://www.mayoclinic.org/tests-procedures/implantable-cardioverter-defibrillators/about/pac-20384692
