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advanced life support (als) > Chapter 10: Cardiac Pacing > Flashcards

Chapter 10: Cardiac Pacing Flashcards

1
Q

What happens when complete heart block occurs at the level of the AV node?

A
  1. HR around 50bpm
  2. Stable escape rhythm - unlikely to suddenly fail and cause asystole
  3. Narrow QRS due to intact bundle branches and bundle of His
  4. May be due to inferior MI
  5. May not need pacing
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2
Q

What can cause complete heart block lower than the AV node?

A
  1. Degenerative conducting fibrosis
  2. Extensive anteroseptal MI - affect all fibres of bundle branches
  3. Cardiomyopathies
  4. Calcific valve disease
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3
Q

What happens in a complete heart block lower than the AV node?

A
  1. Activity from Purkinje fibres or myocardium
  2. Slow and unreliable
  3. Wide QRS
  4. Rhythm can fail transiently causing Syncope (stokes-adams attack) or ventricular standstill and cardiac arrest
  5. Req. urgent pacing - esp. if long ventricular pauses (>3s)
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4
Q

What makes pacing more likely to be successful?

A
  1. Presence of p waves
  2. Heart more likely to respond to pacing stimulus
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5
Q

What does capture mean in reference to pacing?

A
  1. Immediate QRS following pacing stimulus
  2. Check to see if there is a pulse
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6
Q

What are the types of pacing?

A

Non-invasive:
1. Percussion (mechanical - fist)
2. Transcutaneous (electrical)

Invasive:
1. Temporary transvenous pacing
2. Permanent pacing - implanted pacemaker

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7
Q

What are some indications for implanted pacemakers?

A
  1. Treatment of bradycardia
  2. Biventricular pacemakers for HF - cardiac resynchronisation therapy
  3. ICD which have pacing function
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8
Q

When is percussion pacing used in preference to CPR?

A
  1. Bradycardia so profound it causes clinical cardiac arrest
  2. More likely to be successful when ventricular standstill accompanied by p waves
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9
Q

How do you perform percussion pacing?

A
  1. Deliver firm thump to precordium (lateral to lower left sternal edge)
  2. Monitor ECG
  3. 2nd person check for pulse
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10
Q

What should you do if percussion pacing does not promptly trigger return of a pulse?

A
  1. Start CPR immediately
  2. Regardless of whether QRS complexes are generated
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11
Q

When is transcutaneous pacing used?

A
  1. Whilst waiting to establish transvenous pacing
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12
Q

What are the advantages to transcutaneous pacing?

A
  1. Established quickly
  2. Non invasive
  3. Easy to perform
  4. Req. minimal training
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13
Q

What are the disadvantages to transcutaneous pacing?

A
  1. Discomfort in conscious patient - stimulate painful contractions of chest wall muscles
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14
Q

What can be used to deliver transcutaneous pacing?

A
  1. Some defibrillators have ability
  2. Stand-alone pacing devices may be available
  3. Most systems capable of demand pacing - deliver impulse when req.
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15
Q

How do you perform transcutaneous pacing?

A
  1. Ensure area for pads is dry and remove hair
  2. Position pads in same position as defibrillator pads
  3. Use machine as per instructions
  4. Avoid causing movement artefact - may prevent pacing stimulus
  5. Set pacing rate - 60-90bpm typical
  6. Set energy value at lowest value
  7. Gradually increase while observing pt and ECG - until pacing spike followed by QRS and subsequent t wave
  8. Check for pulse

Can be set to 30/40 bpm if sudden ventricular standstill or extreme bradycardia

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16
Q

What is a typical energy range for a transcutaneous pacing device?

A
  1. 50-100mA
17
Q

What should you do if the highest energy on transcutaneous pacing doesn’t achieve electrical capture?

A
  1. Try different electrode positions
  2. If continued - likely myocardium non-viable
  3. Could be caused by other conditions such as severe hyperkalaemia
18
Q

Should you use transvenous pacing during a cardiac arrest?

A
  1. No
  2. Attempt non-invasive before seeking expert help with transvenous pacing
19
Q

What can cause transvenous pacing systems to fail and what is the issue?

A

Fail in 3 ways:

1 High threshold
2 Connection Failure
3 Lead displacement

It may cause cardiac arrest, esp. in those who are pacing dependent

20
Q

When using temporary transvenous pacing, what happens to the pacing threshold?

A
  1. Gradually reduce voltage to minimum to stimulate ventricle
  2. Aim for <1V
  3. Higher indicate insufficient myocardium contact
  4. Pace at 3-4V (higher than the minimum threshold).
  5. Over first days threshold transiently rise
  6. Must check to ensure output remains over the threshold value
21
Q

What should you do if you lose capture due to high threshold?

A
  1. Increase output of cardiac pacemaker
  2. May cause lead displacement so req. expert assistance
22
Q

How can you get connection failure in transvenous pacing?

A
  1. Electrodes usually bipolar - 2 electrodes
  2. Each electrode seperately connected by lead outside patient and inserted into socket and subsequent pacemaker
  3. Failure in any connections can prevent delivery of pacing stimulus
23
Q

When transvenous pacing failure is accompanied with loss of pacing spike, what should you do?

A
  1. Check connections
  2. Check pacemaker not turned off or batteries died
  3. If these not issue, likely fracture in connecting cable - change
24
Q

Where and how is the tip of an endocardial transvenous pacing lead placed?

A
  1. Apex of right ventricle
  2. Must be enough slack in right atrium for movement due to posture change/inspiration but not so much to encourage displacement
25
Q

What is a complication of transvenous pacing?

A
  1. Tip can perforate RV wall and enter pericardium - cardiac tamponade
26
Q

If transvenous pacing fails due to lead displacement or perforation, what is seen?

A
  1. ECG show pacing spike
  2. Likely intermittent or complete loss of capture
  3. If displace but still in RV - can cause ventricular extrasystoles and VT/VF
27
Q

What can happen if transvenous pacing fails?

A
  1. Ventricular standstill
  2. May be short lived and cause syncope
  3. May be prolonged and cause cardiac arrest in asystole

If arrest occurs - use non-invasive pacing until transvenous pacing reestablished

28
Q

Are issues with implanted permanent pacemakers common?

A
  1. No
  2. Connections are much more secure
29
Q

What issues may be seen with implanted permanent pacemakers?

A
  1. Lead displacement - early, less likely over time and rare after 4-6 weeks
  2. Lead fracture - usually following trauma
30
Q

What are the types of implanted pacemaker?

A
  1. Device under clavicle
  2. Leadless - transvenous within RV
31
Q

What are the reasons for having an implanted pacemaker?

A
  1. Treat bradycardia - AV or SA node malfunction
  2. HF - biventricular pacing - cardiac resynchronisation - improve co-ordination of ventricular contraction
32
Q

What can happen if you get a failure in a biventricular pacing system?

A
  1. No major change in HR or dangerous rhythm abnormality

Unlike if implanted pacemaker inserted for bradycardia

33
Q

What is an implanted cardioverter-defibrillator?

A
  1. Device that primarily terminates life threatening tachyarrhythmia’s
  2. Also can deliver pacing stimuli
34
Q

If a patient with an ICD has a cardiac arrest, what should you do?

A
  1. Deliver CPR as normal - no major risk even if ICD deliver shock

Rare reports of shocks from ICD causing transient myalgia and paraesthesiain CPR rescuer

35
Q

What should you consider in patients who have been resuscitated from cardiac arrest in shockable rhythm outside of context of acute MI?

A
  1. ICD implantation
36
Q

What should be done for patients with an ICD after death?

A
  1. Arrange for deactivation
  2. Must be done before removal from body or performance of autopsy
  3. Must be removed before cremation

advanced life support (als) (13 decks)

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