
Overview
This module describes cardioversion, a lower energy shock which aims to cause a synchronised depolarisation throughout the heart tissue, enabling physiological conversion to sinus rhythm. It is delivered synchronous with the patient’s QRS complex to prevent R-on-T phenomenon, which could trigger ventricular fibrillation.
Indications
Contraindications
Patient information and consent
In emergency cardioversion, obtaining informed consent may not be possible. However, patients undergoing elective cardioversion need to give informed consent, and receive premedication for pain.
How do I explain this procedure?
“Your heart is beating too fast and it’s affecting your blood pressure and circulation, making you ill. I need to give you a shock called cardioversion that will reset your heart rate and get it back to its normal speed. We may have to give you medications afterwards to keep it steady. The amount of electricity we use is very low, and will not cause any damage to your body. Because this is not an emergency procedure, you have to sign consent for it.”
What can my patient expect?
“I’m going to give you an injection for pain and to make you drowsy, and then I’ll give you the mild shock. It might make your muscles jerk, but it will not be painful. We will be with you all the time and monitor you continuously.”
What is my patient’s role?
“Tell me if you are allergic to any medications. Stay as calm as possible and cooperate with me.”
Preparation
Follow the Tachycardia Management algorithm to this point. The patient should have:
Synchronised cardioversion may be an emergency procedure. Always:
Site & Positioning
To perform synchronised cardioversion, a patient should be lying flat or reclining on a firm surface with their chest exposed. All clothes, including undergarments, should be removed from the chest.
Procedure
Follow medical asepsis with non-sterile gloves.
Troubleshooting
The patient has a lot of breast tissue.
Always try to place paddles under or lateral to breasts. Large breasts can compromise the effectiveness of the shock delivered.
My patient is soaking wet.
Wipe the patient down quickly before applying paddles.
My patient is so hairy I can’t get contact with the skin.
Use a razor to shave the contact areas, or use any kind of adhesive dressing or pads to “wax” off the worst of the body hair.
My patient is wearing an underwire bra.
Cut it off. The current can run through the underwires, rendering it ineffective, and can cause burns.
My patient has a medication patch on their chest.
Remove it and wipe the area quickly.
My patient has an implanted pacemaker or defibrillator.
Don’t be deterred, but avoid placing your paddles on the device.
My patient is a small child.
Place one paddle on the right second intercostal space, and the other on the back, near the apex of the heart. Check the algorithm for paediatric joules and dosages.
The S or dot indicators are not appearing.
In most emergency settings, the monitor is programmed to default to defib mode. Check that you have activated SYNC mode.
The shock doesn’t deliver/the S or dot indicators are erratic.
The patient’s electrical activity may be too erratic due to ventricular extra-systoles or polymorphic ventricular tachycardia. Call a senior, or if the patient is very unstable with a barely palpable pulse, proceed with unsynchronised defibrillation.
The machine only has pads, not paddles.
Peel off the adhesive sections and stick them in place just like paddles. Keep them on throughout the cardioversion procedure.
Where do I place the three leads?
“Red on the right, green on the spleen, and what’s left on the left.” Place the red electrode on the right shoulder, yellow electrode on the left shoulder, and green electrode on the lower left torso.
I’ve charged, but I decided I don’t want to shock.
Ask an assistant to turn the defibrillator to Monitor instead of Defibrillation. This safely dumps the charge. Do not move charged paddles from the patient’s chest while this is being done.
How do I keep myself and my colleagues safe from electrical accidents?
- Always shout “Clear!” before shocking.
- Always keep oxygen sources at least an arm’s length away (oxygen + electricity can cause explosions).
- Paddles should always be firmly on the patient’s chest, or placed in their rests on the machine. Don’t put paddles down anywhere else.
- Never hold both paddles in one hand.