Cardioversion VS Defibrillation
Cardioversion refers to the use of synchronized electrical shocks to treat arrhythmias that still have a pulse. The timing of the shock must be precisely synchronized with the cardiac cycle.
Defibrillation, on the other hand, is applied during cardiac arrest when the patient presents with pulseless arrhythmias. It delivers asynchronous high-energy shocks to restore effective cardiac rhythm.
The essential difference lies in whether the electrical discharge is synchronized with the cardiac cycle:
· Ventricular fibrillation (VF) and pulseless ventricular tachycardia (VT) require immediate electrical defibrillation.
· Cardioversion is usually applied to rapid arrhythmias with preserved perfusion, including ventricular and supraventricular tachyarrhythmias.
What is a Defibrillator?
A defibrillator is a portable medical device capable of releasing therapeutic electrical current. Its core function is to terminate life-threatening arrhythmias by delivering shocks through electrode pads or paddles to the myocardium. The shock resets abnormal electrical activity, allowing the heart to re-establish an effective rhythm.
Why Are Defibrillators Important?
Ventricular fibrillation and pulseless ventricular tachycardia can instantly eliminate the pumping ability of the heart.
In such cases, electrical defibrillation is the only direct and effective intervention capable of re-establishing a perfusing rhythm.
Early defibrillation has a decisive impact on survival in cardiac arrest patients. For every one-minute delay, the chance of successful resuscitation decreases significantly.
When To Defibrillate?
Defibrillation must be performed immediately when non-traumatic cardiac arrest occurs with pulseless shockable rhythms. Diagnostic indicators include:
· No breathing: absence of chest or abdominal movement
· No pulse: carotid or femoral artery pulse not palpable
· No response: no reaction to verbal commands or painful stimuli
· Unconsciousness: complete loss of awareness, unarousable
What Are the Uses of a Defibrillator?
The primary purpose of a defibrillator is to restore cardiac pumping function lost due to arrhythmia. It specifically targets non-perfusing, lethal rhythms.
By delivering high-energy pulses, the device causes global myocardial depolarization. This interrupts chaotic electrical activity and allows normal pacemaking to resume.
Clinical applications focus on the two shockable rhythms:
- Termination of pulseless ventricular tachycardia
- Elimination of ventricular fibrillation
In professional emergency systems, defibrillators also provide cardiac monitoring and rhythm recognition, supporting advanced life support (ALS) decision-making.
The wide range of device types makes defibrillators suitable for hospitals, ambulance units, and public locations requiring rapid access to defibrillation.
Types of Defibrillators
1. Advanced Life Support Defibrillator (Defibrillator Monitor)
This type functions as a comprehensive emergency platform, combining electrical defibrillation with multi-system monitoring. It is typically used in intensive care units (ICU), emergency departments, and mobile emergency units.
Key monitoring parameters and their clinical relevance include:
· SpO₂ (oxygen saturation): continuous evaluation of tissue perfusion, early warning of hypoxia
· Capnography (end-tidal CO₂): monitoring airway status and CPR effectiveness
· Non-invasive and invasive blood pressure: guiding vasopressor use and monitoring dynamic circulation
· Temperature monitoring: preventing tissue thermal damage caused by repeated shocks
· 12-lead ECG: providing full electrical vector analysis to differentiate supraventricular from ventricular arrhythmias
· CPR feedback: real-time data on compression depth, frequency, and recoil
2. Manual Defibrillator
A manual defibrillator is operated by trained medical professionals. The energy level and discharge are manually adjusted and triggered based on the operator’s interpretation of cardiac rhythm.
Typical applications:
· Complex arrhythmias: torsades de pointes, polymorphic ventricular fibrillation
· Pediatric emergencies: precise energy adjustment according to weight (0.5–4 J/kg)
· In-hospital cardiac arrest: handled by trained physicians or nurses capable of rhythm recognition
· To maximize survival, manual defibrillation must be integrated into high-quality CPR, with interruptions in compressions limited to ≤5 seconds.
Advantages:
· Multifunctionality: integrated synchronized cardioversion, temporary pacing, and drug-enhancement modes
· Advanced performance: impedance compensation for optimal current penetration, biphasic waveform with adjustable pulse width for improved efficiency
· Continuous monitoring: high-resolution displays for ST-segment analysis and rhythm trend diagnosis
Disadvantages:
· Complex operation: requires deep knowledge of antiarrhythmic drugs and electrophysiology
· Limited application: restricted to tertiary hospitals and specialized ambulance teams
3. Automated External Defibrillator (AED)
The AED is a smart public-use device designed to lower the barrier to life-saving intervention. Using voice prompts and automated analysis, it guides untrained individuals to provide defibrillation safely.
Its mission is to shorten the time to first shock in out-of-hospital cardiac arrest, dramatically improving survival in ventricular fibrillation.
Placement of AEDs:
AEDs should be deployed in public areas where the average emergency response time exceeds five minutes. Ideal locations include:
- Stadiums and sports arenas
- Transportation hubs (airports, train stations, subway stations)
- Schools and universities
- Shopping centers and malls
- Religious sites
- Business campuses
- Elderly care and nursing institutions
Access should follow the “1-minute sprint principle”—reachable within one minute.
Advantages:
· User-friendly: voice prompts guide electrode placement, safety clearance, and shock delivery
· Automatic analysis: digital filtering removes movement artifacts, ensuring accurate rhythm detection
· Rapid response: time from power-on to first shock is typically less than 90 seconds
· Error prevention: safeguards against delivering shocks for non-shockable rhythms (asystole, PEA)
· Public availability: in developed countries, there are on average 312 AEDs per 100,000 people
Disadvantages:
· Ongoing costs: periodic replacement of electrode pads and lithium batteries
· Energy limitations: battery efficiency may drop by up to 40% in low-temperature environments
· Fixed mode limitations: cannot manage pacemaker interference or special pediatric rhythms
4. Implantable Cardioverter Defibrillator (ICD)
The ICD is a miniaturized therapeutic system implanted under the skin. It continuously monitors ventricular rhythm and delivers graded shocks automatically in response to ventricular fibrillation or tachycardia.
Provides long-term protection against sudden cardiac death.
Suitable for patients with a high risk of recurrent ventricular arrhythmias.
5. Wearable Cardioverter Defibrillator (WCD)
The WCD is an external device worn on the chest using belt-mounted electrodes. It continuously monitors cardiac rhythm and delivers shocks when life-threatening arrhythmias are detected.
Serves as a temporary protective measure for patients awaiting ICD implantation.
Also used for patients with transient risk of sudden death, such as during post-myocardial infarction recovery.
Conclusion
Electrical defibrillation plays a critical, irreplaceable role in the treatment of cardiac arrest. Its timeliness and precision are vital to maintaining the integrity of the survival chain.
Choosing the right type of defibrillator depends on the clinical or situational context:
· Advanced Life Support Defibrillators meet the needs of critical care monitoring in hospital settings.
· Manual Defibrillators serve specialized medical teams requiring individualized treatment strategies.
· AEDs support immediate community and public response for sudden cardiac arrest.
· ICDs and WCDs provide long-term or temporary individual protection against sudden arrhythmia death.
As a professional medical device supplier, CN MEDITECH focuses on three core defibrillation solutions. Through rigorous selection and continuous technical support, the company builds reliable life support systems for both healthcare institutions and public emergency networks.