Cardioversion vs defibrillation both has the same endpoint, i.e., to deliver electrical energy towards the heart to shock it momentarily, allowing a normal sinus rhythm to kick in. This is made possible via the heart’s natural pacemaker, also known as the sinoatrial node.

Defibrillation Vs Cardioversion

Let’s have a look at defibrillation in detail first.

Defibrillation is the name given to the immediate treatment of lethal arrhythmias. In this condition, the pulse of the patient is lost, i.e., ventricular fibrillation (VF) or pulseless ventricular tachycardia (VT).

Defib is based on the charging of the capacitors and then sending a shock or sudden impulse via paddles in a few milliseconds.

In the era of the 80s, a biphasic waveform was found to give low level energy shocks. They were as effective as monophasic shocks.

Differences between Monophasic and Biphasic Systems

Monophasic systems have a current which travels in one direction only, that is, from one paddle to another.

As far as biphasic systems go, the current moves first towards the positive paddle and then back; this occurs multiple times.

These types of shocks send one cycle per 10 milliseconds. They end up with lesser burns and myocardial damage.

On the contrary, in monophasic shock, the success rate in cardiac arrests is 60% only, whereas in biphasic, it increases to 90%.

However, this efficacy rate of biphasic defibrillators over monophasic ones is non-consistent.

Cardioversion vs Defibrillation

Where is cardioversion used?

  • Decompensated rapid atrial fibrillation that has a fast ventricular response. For example, a hypotensive person does not show any change upon medical therapy.
  • Ventricular tachycardia with a pulse.
  • Supraventricular tachycardia with Atrial fibrillation but without decompensation

When doing cardioversion, the shock should be accurately timed. This is done so that it does not take place during the vulnerable period, which is during the T wave.

How to Cardiovert Successfully

  • For the cardioversion procedure, the person will undergo general anesthesia or sedation.
  • Specialists make sedation decisions.
  • This step is performed in theatres with the help of an anesthesiologist.
  • The majority of cardioversion procedures are elective, but a few are done with acute patients with tachycardia – e.g., chest pain or breathlessness.
  • Turn on the system (machinery) and fix adhesive electrodes.
  • Select an energy level.
  • Wait for a clearly visible trace on the monitor first- e.g., using lead II.
  • Now, click on the ‘sync’ button. At this point, a dot appears on the monitor, marking each QRS complex.
  • It is said that higher starting energy gives a better success rate and needs fewer shocks.
  • Charge according to the condition of the patient.
  • Ensure there is no hindrance around the bed.
  • For discharge or shock, there are chances of 1- to 2-second delay for synchronization.
  • Check after shock rhythm – if it is sinus rhythm, then halt; if not, then send in another shock of high energy levels.
  • Look for any sign of burns afterward and get a 12-lead ECG.
  • Synchronization may not be a success in the case of tachycardia, where the QRS complex has varying morphology.


Look out for any kind of complications related to cardioversion vs defibrillation. Contact experts from Epic Heart and Vascular Center in case you have more queries.