How to perform an ECG

Major components of an ECG machine include ..

• Power button

• Display screen - to view the ECG trace

• Paper supply and speed - to print out the ECG (25mm/s is recommended for most patient but 50mm/s should be used for higher heart rates to spread out the complexes as this is faster

• Automatic/manual settings - to choose how to display the ECG (on screen or printed)

Patient Preparation - Calm and relaxed

Avoid false readings, increase in heartrate if they’re stressed

Patient Preparation - Quiet environment

• Allow them to be calm and relaxed as possible

• Avoid high traffic areas, e.g. prep room

Patient Preparation - Assess heart rate and rhythm prior to beginning the ECG

• Indication as to if you placed the ECG correctly

• To gain a baseline

• Heart rate and rhythm before placing the ECG

Patient Preparation - Positioned in right lateral recumbency

• Least amount of stress on the heart due to where it is positioned

• In some circumstances this is impossible - standing, left lateral

• If not in Right lateral let the vet know what position the patient was in - if any abnormalities are noticed, this could be why

Patient Preparation - Lay on an electrically insulated surface (rubber matting plus a thick bed)

• Patient grip

• So we’re only measuring the patients electrical activity

• Not picking up any other other, e.g. phone

Patient Preparation - Limbs perpendicular to the body and parallel, limbs not in contact

• Legs could get tangled in the leads

• Could get artifacts

Patient Preparation - Patient must remain as still as possible

• Prevent increase in heartrate

• Any artifact could occur

• Electrical interference

Patient Preparation - Alter positioning technique for dyspnoeic and uncooperative patients

Standing up or sitting down - dyspnoea patients

Patient Preparation - Consider the effect of anaesthetic and sedative drugs

Effect of opioids on heart rate and rhythm, avoid drugs if possible

Electrodes

• Required to connect the ECG leads to the patient

• Crocodile clips and self-adhesive electrodes most used

Electrodes - Record the electrical activity generated by the heart ..

Body fluids and tissues are good conductors of electricity, and this can be detected via electrodes

Crocodile clips - Advantages

• Good electrical connection

• Less risk of disconnection

• Moderna clips more conformable

• Reusable

Crocodile clips - Disadvantages

• Bite can be painful

• Uncomfortable

• May result in skin necrosis in cases of prolonged use

• Unadvised if left on for more than 5-10 minutes as it pinches the skin

Self-adhesive Electrodes - Advantages

• Relatively comfortable

• Non-invasive (placed in footpads)

• Can be used for longer-term monitoring

Self-adhesive Electrodes - Disadvantages

• Disposable = £££

• Some patients do not like to have their feet touched

To ensure good electrical conductance ..

70& isopropyl alcohol (surgical spirit), or conductive gel (ECG, KY jelly, ultrasound gel) should be applied to the electrodes

When using crocodile clips, position them over ..

Bony prominences - muscle contracts, bone doesn't - can get muscle artifacts

Spirit VS Conductive gel

• Spirit - Evaporates, flammable (but cheap!)

• Conductive gel - Less evaporation, may require hair clipping

Why might conductive gel be better for cats compared to surgical spirit?

They do not often tolerate the strong alcohol odour

Once the electrodes have been placed ..

They must not be touching any other part of the patient of the handler - do not position the leads over the patient