Cardiac Pacing

Question 1

Recap the cardiac conducting system

Question 1

What is the purpose of non-invasive cardiac pacing ?

Answer 1

It can be used to maintain cardiac output temporarily while expert help to deliver longer-term treatment is obtained

Question 2

What are the different levels CHB can occur and how does this influence risk?

Answer 2

• CHB can occur at the level of the AV node, automaticity of pacemaker cells immediately below the AV node become the new pacemaker cells. They produce a relatively fast heart rate 40-50bpm. Resultant escape rhythm is relatively stable with narrow QRS complexes and unlikely to fail/cause asystole.
• CHB occuring lower than the bundle of His (bundle branches and purkinje fibres) produce escape rhythms which are slow and unreliable. Broad QRS complexes are seen. This is because the impulses produced by these pacemaker cells are slow. There is a risk of transient failing causing syncope (stokes adams attack) or complete failure, causing ventricular standstill and cardiac arrest.

Question 3

Does narrow QRS complex CHB require treatment ?

Answer 3

Not always, it depends if the bradycardia is causing any symptoms/instability.

Question 4

What should be done for all broad QRS complex CHB ?

Answer 4

Cardiac pacing

Question 5

What does the occurence of long ventricular pauses (>3s) in the content of CHB require?

Answer 5

Urgent cardiac pacing, high risk of asystole.

Question 6

What are the different modes of cardiac pacing ?

Answer 6

Non-invasive:
* Percussing pacing ‘fist pacing’
* Transcutaneous pacing

Invasive:
* Temporary transvenous pacing
* Permanent pacing - ICD, CRT, PPM

Question 7

If a pacing stimulus induces an immediate QRS complex what is this referred to as ?

Answer 7

Capture

Question 8

Why should transcutaneous pacing be used for as short a time as possible before getting more definite pacing?

Answer 8

Because it provides unreliable ventricular stimulation.

Question 9

When carrying out cardiac pacing what should you regularly remember to check for ?

Answer 9

A pulse!

Question 10

Describe how to perform percussion pacing

Answer 10

Question 11

What are the advantages of transcutaneous pacing?

Answer 11

• Can be established very quickly.
• Widely available
• Easy to perform and requires minimal training
• Can be initiated by healthcare professionals whilst awaiting expert help for transvenous pacing

Question 12

What is the main disadvantage of transcutaenous pacing ?

Answer 12

It causes painful muscle contraction of the chest wall muscles.

Question 13

Describe the steps on how to perform transcutaenous pacing

Answer 13

Question 14

Is it appropriate to attempt transvenous pacing during a cardiac arrest?

Answer 14

No - attempt to achieve cardiac output with transcutanous then seek expert help

Question 15

Temporary transvenous pacing systems can fail, what are the potential causes of this ?

Answer 15

1. High threshold - electrode may not be making adequate contact with the myocardium
2. Connection failure - of any of the leads/connections to the pacemaker.
3. Lead displacement - note lead can perforate the right ventricle too.

Question 16

What are the 2 main types of cardiovascular implanted electronic devices?

Answer 16

PPM
ICD

Question 17

What is important to establish about why a PPM was inserted?

Answer 17

Determine if inserted for bradyarrhytmia or heart failure.

Question 18

If a patient with a implanted cardiovascular electronic device suffers a cardiac arrest or needs cardioversion what should you do for defib pad placement ?

Answer 18

Place >8cm away from device.
If needed use A-P defib pad position.

Question 19

What is the purpose of a CRT pacemaker and will damaging it during a resus attempt likely cause harm ?

Answer 19

CRT pacemakers are used to improve cardiac efficiency by resynchronising the contracting ventricles. Failure of this pacemaker will not usually cause any major change in HR or result in dangerous arrythmias.

Question 20

What is the function of a ICD?

Answer 20

*** Deliver shocks to terminate a life-threatening tachycarrythmia. **
* Also function as demand pacemaker
* May also deliver biventricular pacing for heart failure.
* Additionally will deliver defibrillation if required.

Question 21

What are the indications for a ICD?

Answer 21

• Primary prevention of cardiac arrest - people at high risk of VF or VT
• Select patients post MI
• Certain inherited cardiac conditions

Question 22

If a patient has a cardiac arrest that is not terminated by the ICD what should you do ?

Answer 22

Deliver CPR and external defibrillation as usual

Question 23

During CPR if an ICD delivers repeated inappropriate shocks impeding delivery of high quality CPR what should be done ?

Answer 23

Deactivate it using a ring magnet - hold or tape the magnet on the skin overlying the device.

Question 24

What should any patient who has been resusitated from a shockable rhythm outside of the contect of STEMI?

Answer 24

Refer to cardio for consideration of ICD.