Chapter 10 Flashcards
(13 cards)
What is a Stokes-Adams attack?
Syncope often secondary to complete heart block with broad QRS complexes
When is cardiac pacing indicated?
Broad complex complete heart block, especially with long ventricular pauses (>3 seconds) as this implies risk of asystole
Peri-arrest with bradycardia where not responding to bradyarrhythmia algorithm
Cardiac arrest where P waves are present
Capture definition
When pacing stimulus induces an immediate QRS complex
List methods of cardiac pacing
Non-invasive
* Percussion pacing (‘fist pacing’)
* Transcutaneous pacing
Invasive
* Temporary transvenous pacing (internal temporay transvenous/externalised permanent trans-venous, endocardial systems or surgical epicardial systems)
* Permanent pacing (using an implanted pacemaker)
When is percussion pacing recommended? How is it performed?
Cardiac arrest due to bradycardia. More likely to be successful when ventricular standstill is accompanied by continuing P waves.
Deliver firm repeated thumps to the precordium with the side of a closed fist, just lateral to the lower left sternal edge
Raise hand 20cm above chest before each thump
Monitor ECG to see if QRS complex is generated by each thump - if not try harder, then move point of contact until ventricular stimulation produced on ECG
Feel for pulse.
If not producing regular pulse start CPR immediately.
Advantages of non-invasive pacing vs transvenous pacing
Can be established quickly
Widely available
Easy to perform and requires minimal training - can be initiated by many healthcare providers
Is transcutaneous pacing pleasant for the patient?
No it’s uncomfortable - chest wall muscle contraction, direct discomfort
How is transcutaneous pacing performed?
Warn patients they are likely to experience discomfort, give IV analgesia/sedation if required
Remove chest hair and ensure dry skin in area where electrode will be applied
May need to have additional ECG monitoring electrodes
Attach pads in conventional position - right pectoral and apical position. If using a pacing device not capable of defibrillation use A-P position to allow defib pads to remain in place
Avoid movement artefact - can be detected by device as QRS complex
Select appropriate pacing rate - usually 60-90 per minute (may be less during complete ventricular standstill or extreme bradycardia)
Set energy output at lowest value, gradually increase the output while monitoring the patient and ECG, increase until each spike is followed by QRS (typically with current of 50-100mA)
Check that QRS complex is followed by T wave
If highest current setting is reached and no electrical capture try changing electrode position - may not work if non-viable myocardium or severe hyperkalaemia
If achieving electrical capture check that the QRS complex is followed by a pulse - if no pulse this is PEA
If necessary can give chest compressions - no hazard from contact with the patient. No benefit in trying to give transcutaneous pacing during chest compressions, should turn of pacemaker while CPR in progress
When adequate cardiac output seek help to arrange emergency transvenous pacing
Should transvenous pacing be initiated during a cardiac arrest?
Usually not appropriate - should use non-invasive pacing to achieve cardiac output then use transvenous pacing
How do temporary transvenous pacing systems fail?
High threshold - usually aim for threshold of <1V, if higher suggests electrode is not making good contact with the myocardium so may need to reposition the lead.
Connection failure - will show absence of pacing spike
Lead displacement - lead can perforate the wall of the right ventricle and enter the pericardium. Can cause tamponade.
How does tranvenous pacing lead displacement present?
Recently implanted pacing lead, cardiac arrest with PEA
ST elevation on ECG
Pacing spike on ECG but intermittent or complete loss of capture
Can cause ventricular extrasystoles or VT/VF
Risk of ventricular standtill causing syncope or cardiac arrest and asystole
How should ICDs be managed during a cardiac arrest?
If ICD fails to terminate cardiac arrest deliver CPR as usual.
Rare reports of shocks from ICD causing myalgia/paraesthesia in CPR deliverer
Deliver shock if shockable - position defib pads away from device
If ICD is delivering repeated ineffective shocks which are impeding delivery of CPR can use ring magnet to deactivate - do not delay or interrupt CPR to do this
Management of ICDs after death
Need to be deactivated by cardiac physiologist
