Step by step guide for Synchronised DC Cardioversion

By: Martin GrantStudent no. 40077467

Cardioversion is defined as a “synchronised direct current (DC) discharge, and … does not apply to ventricular defibrillation or to the pharmacologic reversion of arrhythmias.”

It is synchronised to give electrical discharge at the point of the Q or R wave in the ECG cycle.

The reason to synchronise this is to prevent a shock occurring during repolarisation of ventricles in the T wave, which can lead to Ventricular Fibrillation.

What is Cardioversion?1

The ECG

Left shows the various waves throughout the ECG and explains what each deflection means from the isoelectric line.

Right shows another ECG but with colour demonstrates the duration of each different segment.

Fig 1

Fig 2

Based on advanced cardiac life support (ACLS) guidelines, any patient with narrow or wide QRS complex tachycardia (ventricular rate >150) who is unstable (for example, chest pain, pulmonary oedema, lightheaded, hypotension) should be immediately treated with synchronized electrical cardioversion.

Indications2

Supraventricular tachycardia due to re-entry Atrial fibrillation Atrial flutter Atrial tachycardia Monomorphic VT with pulses

Contraindications Digoxin toxicity–associated tachycardia Sinus tachycardia caused by various clinical

conditions Multifocal atrial tachycardia

Also recommended in the following:

Midaxillary line

Important body landmarks

• Right Sternal edge• Intercosta

l spaces

First of all, the appropriate equipment must be organised:◦ IV access◦ Airway management equipment◦ Sedative drugs (midazolam and fentanyl)◦ Cardioversion monitoring device

Procedure

Place patient onto bed Remove upper garments Apply heart tracing leads

Step 1

Conduction strips

Points of application

Leads: Red, Amber, Green (Traffic lights)

Turn the Cardioversion machine on

Step 2

Twist green nozzle clockwise to

activate

Off

Place on the pads

Step 3

Pads and connection for

machine

First pad: 2nd or 3rd intercostal space, Right Sternal edge

Second pad: 4th or 5th Intercostal space ,Midaxillary line

Anterolateral pad positioning

Check heart tracing is being picked up

Step 4

Press Sync to locate R waves

Step 5R waves indicated by arrows

Set the voltage as per guidelines on the condition presenting with the patient

Step 6

WARN EVERYBODY AROUND THE BED YOU ARE ABOUT TO PRESS CHARGE AND SHOCK

Everyone should step back from the patient and the bed

Step 7

Press Charge Then Shock

Step 8

Watch the monitor and see if the Rhythm has returned to normal

If not, this may need to be repeated

Below is a before and after ECG from a patient in AAH with Supraventricular tachycardia resolved using Synchronised DC Cardioversion

Step 9

Pre-Cardioversion ECG

Post-Cardioversion ECG

Synchronised cardioversion when practiced correctly can be a very effective way to correct tachycardia’s.

ACLS guidelines should be followed for when it should be used and at which voltage.

Always check for the contraindications prior to the procedure.

Follow the steps above for the correct way to perform the procedure safely and effectively.

Conclusion

1. Lown B. Defibrillation and cardioversion. Cardiovasc Res. Aug 1 2002;55(2):220-4.

2. [Guideline] Part 5: Electrical Therapies. Automated External Defibrillators, Defibrillation, Cardioversion, and Pacing. Circulation. 2005;112:IV-35-IV-46.

Figures3. http://hyperphysics.phy-astr.gsu.edu/hbase/

biology/imgbio/ecg.gif

References