Cardiac pacing Flashcards
What is the intrinsic rate of the SA node?
60-70min-1
What is the intrinsic rate of the purkinje fibres?
0-30min-1
What is the intrinsic rate of the AV junctional region?
40-50min-1
What kind of CHB requires pacing?
broad-complex
the occurence of long pauses >3 s makes this need urgent
Why should transcutaenous pacing be used as briefly as possible?
It does not produce reliable ventricular stimulation
When should percussion pacing be performed?
When bradycardia is so profound it causes cardiac arrest
more likely to be successful when ventricular standstill is accompanied by continuing p wave activity
How is percussion pacing performed?
- With the sides of a closed fist deliver repeated thumps to the praecordium (lateral to the lower left sternal edge)
- raise the hand about 20cm in between thumps
- monitor the ECG and assess whether a QRS complex is generated (if possible this should be a second person)
- if initial thumps do not produce a QRS complex try using slightly harder thumps
- if this still fails to produce a QRS move the point of contact until a point is found that produces ventricular stimulation
What are the advantages of transcutaenous pacing as opposed to transvenous?
- It can be established very quickly
- it is widely available
- it is easy to perform and requires minimum tracing
- it can be initiated by healthcare providers whilst awaiting transvenous pacing
What is the major disadvantage of transcutaenous pacing?
In a conscious patient it is very uncomfortable
What should you bear in mind if your pacing device cannot defibrillate?
Position AP so that you can still defibrillate
If artefact is continuing to prevent your pacing device from working- what should you do?
Switch it to deliver fixed-rate pacing
What is usually an appropriate pacing range?
60-90
If the pacing device has an adjustable energy output what should you do?
Set it to its lowest value and turn on the pacemaker
Gradually increase the output whilst observing the patient and the ECG
Increase the current until each pacing spike is followed by a QRS
How do you know if your QRS complex is genuine and not artefact?
It is followed by a T wave and generates a pulse
If the highest current setting is reached and capture has not occured, what should you do?
change the electrode positions
continued failure to capture may indicate mypcardial inviability or hyperkalaemia
Should you perform CPR while pacing?
You can but there is no benefit, best to turn off the pacer
What should be done when an adequate cardiac output is generated via trans-cutaenous pacing
seek expert help to establish transvenous pacing
What are the three ways temporary transvenous pacing methods can fail?
- high threshold
- connection failure
- lead displacement
What is the aim for the threshold of transvenous pacing
<1.0 V
When is it normal to pace the heart at higher thresholds?
Over the first days and weeks after insertion
How often should the threshold on temporary pacing leads be checked?
Daily
If loss of capture occurs bevause of a high threshold what should you do?
- increase the output of the pacemaker to well about the threshold
- obtain a CXR and get expert help
What is connection failure seen as on ECG
Absence of pacing spike
What should you do if there is a absence of a pacing spike?
Check pacemaker is on
Check connectoins
Chack batteries aren’t deplete
Try another pacing box
Where is the tip of an endocardial transveour ventricular pacing lead normally placed?
Apex of the right ventricle
If a patient with a recently inserted pacemaker suffers a PEA cardiac arrest what should be considered?
Perforation of the myocardium and tamponade
What is likely to be seen on an ECG in lead displacement
A pacing spike with intermittent or complete loss of capture
What should be done if transvenous pacing has caused asystole
Use transcutaenous until pacing can be re-established
When is lead displacement less likely after permanent pacemaker insertion?
After 4-6 weeks
What can trigger a fracture of a permanent pacing lead?
foosh on the side of the pacemaker
What kind of pacemakers are undetactable on examination?
Leadless pacemakers
How far away should defibrillation pads be placed from an ICD?
> 8cm
When should you consider deactivating an ICD in CPR
If it delivers repeated inappropriate shocks that are impeding delivery of high quality CPR
