Chapter 10: Cardiac Pacing Flashcards

1
Q

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

A

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 req. pacing

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2
Q

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

A

Degenerative conducting fibrosis

Extensive anteroseptal MI - affect all fibres of bundle branches

Cardiomyopathies

Calcific valve disease

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3
Q

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

A

Activity from Purkinje fibres or myocardium (intrinsic rate of 30BPM)

Slow and unreliable

Wide QRS

Fail transiently to cause Syncope (stokes-adams attack) or ventricular standstill and cardiac arrest

Req. urgent pacing - esp. if long ventricular pauses (>3s)

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4
Q

What makes pacing more likely to be successful?

A

Presence of p waves - heart more likely to respond to pacing stimulus

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5
Q

What does capture mean in reference to pacing?

A

Immediate QRS following pacing stimulus

Check to see if there is a pulse

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6
Q

What are the types of pacing?

A

Non-invasive:

  • Percussion (mechanical - fist)
  • Transcutaneous (electrical)

Invasive:

  • Temporary transvenous pacing
  • Permanent pacing - implanted pacemaker
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7
Q

What are some indications for implanted pacemakers?

A

Treatment of bradycardia

Biventricular pacemakers for heart failure - cardiac resynchronisation therapy

Implanted cardioverter defibrillator which have pacing function

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8
Q

When is percussion pacing used in preference to CPR?

A

Bradycardia so profound it causes clinical cardiac arrest

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

Deliver firm thump to precordium (lateral to lower left sternal edge)

Monitor ECG and 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

Start CPR immediately regardless of whether QRS complexes are generated

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11
Q

When is transcutaneous pacing used?

A

Whilst waiting to establish transvenous pacing

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12
Q

What are the advantages to transcutaneous pacing?

A

Established quickly
Non invasive
Easy to perform and req. minimal training

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13
Q

What are the disadvantages to transcutaneous pacing?

A

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

Some defibrillators have ability

Stand-alone pacing devices may be available

Most systems capable of demand pacing - deliver impulse when req.

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15
Q

How do you perform transcutaneous pacing?

A

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, can be 30/40 if sudden ventricular standstill or extreme bradycardia

Set energy value at lowest value (50-100mA), gradually increase as observing pt and ECG - until pacing spike followed by QRS and subsequent t wave

Check for pulse

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16
Q

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

A

50-100mA

17
Q

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

A

Try different electrode positions

If continued - likely myocardium non-viable

Could be caused by other conditions such as severe hyperkalaemia

18
Q

Should you use transvenous pacing during a cardiac arrest?

A

No - attempt non-invasive before seeking expert help with transvenous pacing

Transvenous pacing - pacing wire is inserted into heart via vasculature.

19
Q

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

A

It may cause cardiac arrest, esp. in those who are pacing dependent. Fail in 3 ways:

1 High threshold
2 Connection Failure
3 Lead displacement

20
Q
A
21
Q

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

A

Increase output of cardiac pacemaker

May cause lead displacement so req. expert assistance

22
Q

How can you get connection failure in transvenous pacing?

A

Electrodes usually bipolar - 2 electrodes

Each electrode seperately connected by lead outside patient and inserted into socket and subsequent pacemaker

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

Check connections
Check pacemaker not turned off or batteries died

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

Apex of right ventricle

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

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

ECG show pacing spike

Likely intermittent or complete loss of capture

If displace but still in RV - can cause ventricular extrasystoles and VT/VF

27
Q

What can happen if transvenous pacing fails?

A

Ventricular standstill

May be short lived and cause syncope

May be prolonged and cause cardiac arrest in asystole - if so use non-invasive pacing until transvenous pacing reestablished

28
Q

Are issues with implanted permanent pacemakers common?

A

No as the connections are much more secure

29
Q

What issues may be seen with implanted permanent pacemakers?

A

Lead displacement - early, less likely over time and rare after 4-6 weeks

Fracture of permanent pacing lead - usually following trauma

30
Q

What are the types of implanted pacemaker?

A

Device under clavicle

Leadless - transvenous within RV

31
Q

What are the reasons for having an implanted pacemaker?

A

Treat bradycardia - AV or SA node malfunction

Heart failure - 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

Doesn’t lead to major change in HR or dangerous rhythm abnormality

Unlike if implanted pacemaker inserted for bradycardia

33
Q

What is an implanted cardioverter-defibrillator?

A

Device that primarily terminates life threatening tachyarrhythmia’s but also can deliver pacing stimuli

34
Q

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

A

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

Rare reports of shocks from ICD causing transient myalgia and paraesthesia

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

ICD implantation

36
Q

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

A

Arrange for deactivation

Must be done before removal from body or performance of autopsy

Must be removed before cremation

37
Q

What are the reasons for an ICD

A

Primary prevention for - sudden cardiac death
MI with HF

38
Q
A