Cardioversion as Emergency Therapy

Two rescuers treat an elderly man with MEDUCORE Standard²

With life-threatening arrhythmias such as ventricular fibrillation, resuscitation must be initiated immediately. Yet even arrhythmias with less serious consequences call for proper treatment – with the emergency medical services, the military medical corps, and in hospital. Cardioversion is used with various indications to bring the heart back to a sinus rhythm.

MEDUCORE Standard² from WEINMANN supports you with electric cardioversion in a reliable and user-friendly way.

What is a cardioversion?

Cardioversion is a medical procedure for restoring normal heart rhythm in the event of arrhythmias. With arrhythmias such as atrial fibrillation, stimulus propagation from the sinus node is uncontrolled, disrupting the heart’s sinus rhythm. A cardioversion then aims to normalize the activity of the sinus node so that heart again beats in a regular rhythm. 


A cardioversion is used with various indications. These typically include:

  • Ventricular tachycardia
  • AV nodal reentry tachycardia
  • Ventricular tachycardia
  • Symptomatic atrial fibrillation
  • Atrial flutter
  • WPW syndrome


A cardioversion must not be performed with:

  • Digitalis poisoning
  • Presence of blood clots
  • Overactive thyroid (hyperthyroidism)
  • Fitted pacemaker

Forms of cardioversion

A distinction is drawn between two main types of cardioversion:

  1. Pharmacological cardioversion
  2. Electrical cardioversion

Pharmacological cardioversion is achieved through medication, lasts longer, and is therefore not common in emergencies. Electrical cardioversion delivers an electrical shock and can be used in emergencies and electively. The success rate with electrical cardioversion is much higher than with pharmacological cardioversion1.

 1. Pharmacological cardioversion

The medication for pharmacological cardioversion – known as an antiarrhythmic drug – is mainly divided into in four classes, each of which differs by virtue of its mechanism of action:

Class I

Mechanism of action:
Sodium channel blocker

e.g., flecainide, propafenone, procainamide, lidocaine

Class II

Mechanism of action:

e.g., metoprolol

Class III

Mechanism of action:
Potassium channel blocker

e.g., amiodarone, ibutilide

Class IV

Mechanism of action:
Calcium channel blocker

e.g., verapamil

2. Electrical cardioversion

With electrical cardioversion the sinus rhythm is restored with a direct current pulse. There are two different versions:

a. External electrical cardioversion

External electrical cardioversion delivers electrical shocks using electrodes on the chest wall after previous analgosedation.


b. Internal electrical cardioversion

Internal electrical cardioversion is performed if external cardioversion does not have the desired effect. A catheter is inserted through the inguinal vein to the heart. This catheter is then used to deliver electric shocks.

As part of internal electrical cardioversion, implantable cardioverters/defibrillators (ICD) can also be used.

Why is cardioversion important?

Cardioversion is an important medical procedure for restoring the sinus rhythm in the case of serious arrhythmias which may be life-threatening or which, in the case of atrial fibrillation, increase the risk of blood clots and strokes if untreated.

Electrical cardioversion has a much higher success rate than treatment with antiarrhythmic drugs. According to the Deutsches Ärzteblatt journal, pharmacological cardioversion produces a sinus rhythm in around 70% of patients while the figure is more than 85%2 with electrical cardioversion.

Other studies come to similar conclusions and also demonstrate that the treatment duration in cases such as acute atrial fibrillation is much shorter with electrical cardioversion than with pharmacological cardioversion3

How do you perform a cardioversion?

If a cardioversion is performed electively, anticoagulant medication is administered beforehand both with pharmacological and electrical cardioversion. This is important as thrombi (blood clots) often form in the atria particularly with patients with atrial fibrillation. These thrombi can lead to an embolism through to a stroke.

A transesophageal echocardiogram (TEE) is also performed before a cardioversion to rule out intraatrial thrombi.

A pharmacological cardioversion is only used with hemodynamic stable patients and usually only electively. The antiarrhythmic drug is administered orally or intravenously. Depending on the drug’s mechanism of action, the active ingredient blocks certain receptors relevant for nerve conduction or blocks ion channels so that the heart activity is normalized and the sinus rhythm restored.

An electrical cardioversion is used on an outpatient basis as an elective procedure or as an emergency treatment with antiarrhythmic drug-resistant ventricular tachycardia. In both cases, the treatment is performed under short anesthesia using a defibrillator and is monitored via an ECG. The defibrillator delivers an electrical shock of 125 to 200 joules synchronously with an R wave – depending on the indication. If delivery of a single shock is not sufficient to restore the sinus rhythm, a second shock with higher energy is delivered.

The recommendation for patients at particular risk of stroke or recurrence is to keep taking anticoagulants for several weeks after the electrical cardioversion.


Cardioversion is a safe procedure with few side-effects. These include:

  • Arrhythmias (e.g., asystole or ventricular tachycardia)
  • Embolisms due to released blood clots through to a stroke


WEINMANN – Cardioversion devices

MEDUCORE Standard² in cardioversion

A life-threatening arrhythmia or cardiac arrest with ventricular fibrillation requires immediate and appropriate intervention.

MEDUCORE Standard² from WEINMANN assists you with all steps of an electrical cardioversion both with prehospital emergencies and with mobile care in hospital or with the medical services in military medical corps.

The Advanced life support from MEDUCORE Standard² supports 12-lead ECG and manual defibrillation and cardioversion. If manual mode is enabled, a cardioversion – either with synchronized shock delivery – can be performed with a set energy of 1 to 200 joules.

Light, space-saving and rugged: MEDUCORE Standard² combines high-end functionality with user-friendly operation. The compact monitor/defibrillator has all the necessary functions for prehospital and in-hospital patient monitoring and enhanced diagnostics.

WEINMANN has been developing reliable and user-friendly medical devices for emergency medicine for more than 45 years. The emergency medicine devices from WEINMANN are matched optimally in terms of their functionality and can be combined with virtually any of the respective portable units tailored to each application. They are also compact and rugged, and fast, easy, and intuitive to operate.

Contact person with headset

Interested in MEDUCORE Standard²?

If you would like individual advice on MEDUCORE Standard², do not hesitate to contact us directly.


1 Bellone A, Etteri M, Vettorello M, Bonetti C, Clerici D, Gini G, et al. Cardioversion of acute atrial fibrillation in the emergency department: A prospective randomised trial. Emergency Medicine Journal. 2012 Mar;29(3):188–91.

2 Klein HH, Trappe HJ: Cardioversion in non-valvular atrial fibrillation. Dtsch Arztebl Int 2015; 112: 856–62

3 A. Bellone et al.: Cardioversion of acute atrial fibrillation in the emergency department: a prospective randomised trial. Emerg Med J 2012 Mar; 29(3): 188–91