Chapter 10: Cardiac Pacing Flashcards
What happens when complete heart block occurs at the level of the AV node?
- HR around 50bpm
- Stable escape rhythm - unlikely to suddenly fail and cause asystole
- Narrow QRS due to intact bundle branches and bundle of His
- May be due to inferior MI
- May not need pacing
What can cause complete heart block lower than the AV node?
- Degenerative conducting fibrosis
- Extensive anteroseptal MI - affect all fibres of bundle branches
- Cardiomyopathies
- Calcific valve disease
What happens in a complete heart block lower than the AV node?
- Activity from Purkinje fibres or myocardium
- Slow and unreliable
- Wide QRS
- Rhythm can fail transiently causing Syncope (stokes-adams attack) or ventricular standstill and cardiac arrest
- Req. urgent pacing - esp. if long ventricular pauses (>3s)
What makes pacing more likely to be successful?
- Presence of p waves
- Heart more likely to respond to pacing stimulus
What does capture mean in reference to pacing?
- Immediate QRS following pacing stimulus
- Check to see if there is a pulse
What are the types of pacing?
Non-invasive:
1. Percussion (mechanical - fist)
2. Transcutaneous (electrical)
Invasive:
1. Temporary transvenous pacing
2. Permanent pacing - implanted pacemaker
What are some indications for implanted pacemakers?
- Treatment of bradycardia
- Biventricular pacemakers for HF - cardiac resynchronisation therapy
- ICD which have pacing function
When is percussion pacing used in preference to CPR?
- Bradycardia so profound it causes clinical cardiac arrest
- More likely to be successful when ventricular standstill accompanied by p waves
How do you perform percussion pacing?
- Deliver firm thump to precordium (lateral to lower left sternal edge)
- Monitor ECG
- 2nd person check for pulse
What should you do if percussion pacing does not promptly trigger return of a pulse?
- Start CPR immediately
- Regardless of whether QRS complexes are generated
When is transcutaneous pacing used?
- Whilst waiting to establish transvenous pacing
What are the advantages to transcutaneous pacing?
- Established quickly
- Non invasive
- Easy to perform
- Req. minimal training
What are the disadvantages to transcutaneous pacing?
- Discomfort in conscious patient - stimulate painful contractions of chest wall muscles
What can be used to deliver transcutaneous pacing?
- Some defibrillators have ability
- Stand-alone pacing devices may be available
- Most systems capable of demand pacing - deliver impulse when req.
How do you perform transcutaneous pacing?
- Ensure area for pads is dry and remove hair
- Position pads in same position as defibrillator pads
- Use machine as per instructions
- Avoid causing movement artefact - may prevent pacing stimulus
- Set pacing rate - 60-90bpm typical
- Set energy value at lowest value
- Gradually increase while observing pt and ECG - until pacing spike followed by QRS and subsequent t wave
- Check for pulse
Can be set to 30/40 bpm if sudden ventricular standstill or extreme bradycardia