Pacemakers and LVAD's Flashcards
What is undersensing and what causes it?
When the PPM doesn’t sense underlying rhythms and attempts to pace over an intrinsic rhythm
Programming issues
Lead displacement
New bundle branch block
Stimulation threshold too high
What can be seen on ECG with undersensing?
Pacemaker spikes within native QRS complexes
R on T leading to Torsades
What is oversensing and what causes it?
When the PPM interprets inappropriate signals as QRS’s and doesnt pace
Very large P or T waves
Lead contact issues
Significant skeletal muscle activity
What is seen on an ECG with oversensing?
Technically nothing, although native rhythm will be evident due to no pacing
What is output failure and what causes it?
When a paced stimulus is not generated
Interference, lead displacement/fracture, oversensing
What is failure to capture and what causes it?
When a paced stimulus reaches the myocardium but does not cause depolarisation
Acidaemia, electrolyte abnormalities, ischaemia, lead displacement/fracture, exit block
What is pacemaker-mediated tachycardia and how is it treated?
When the pacemaker (antegrade) forms a re-entrant tachycardia with the AV node (retrograde), occurs when retrograde p waves are interpreted as native atrial activity
Treated with AV blockers (adenosine) or magnet attachment
What is sensor induced tachycardia and how is it treated?
PPM can increase the rate in response to physiological stimuli (exercise etc)
May oversense these stimuli and increase rate inappropriately
eg vibrations, electrocautery, limb movement, hyperventilation
Magnet will terminate, or remove stimulus
What is runaway pacemaker and how is it treated?
When an older PPM’s battery is failing it releases paroxysms of low amplitude stimuli at rates over 200
Can cause tachycardia, TdP, VF and paradoxically bradycardia if the stimulus is too low amplitude to produce capture
Magnet temporary fix, needs new battery
What are Lead displacement dysrhythmias and how are they treated?
If the lead is pulled back and floats freely in the RV it will intermittently pace, cause ectopics and possibly VT due to tickling of the myocardium
If the lead has eroded through the septum will get intermittent RBBB and LBBB patterns
Requires lead removal
What is Pacemaker syndrome and how is it treated?
AV dyssynchrony and loss of atrial kick due to improper timing of A leads and V leads
Often characterised by drop in BP and pre-syncope when pacing kicks in relative to native rhythm
Needs programming fixed
What is Twiddlers syndrome?
Patient manipulation (accidental or deliberate) of the generator, usually in a twisting motion on its long axis
Leads to dislodgement of pacing leads and thus lack of pacing as well as pacing of unintended structures such as the diaphragm or skeletal muscles
What is the pacing mode nomenclature and what does it mean?
1st letter = Chambers paced
2nd letter = Chambers sensed
3rd letter = Response to sensing
ie DOO (dual paced, nil sensing and no response to sensing)
VVI (ventricle paced, ventricle sensed, inhibit pacing if senses intrinsic activity)
Some newer PPMs have further nomenclature
4th letter = rate modulation (non O vs modulated R)
5th letter = Multisite pacing (O/A/V/D)
What does the placement of a magnet usually do to a PPM?
Varies with different set ups, but usually turns the PPM to asynchronous pacing (ie VOO, DOO)
Risk of TdP and pacemaker induced tachycardia
What does a magnet do to an ICD?
Varies but usually it deactivates the defibrillation function
What is the difference in appearance between atrial and ventricular pacing?
Atrial spikes occur before the p wave, p wave often appears normal, QRS usually narrow complex
Ventricular spikes occur before QRS and after native p waves
R sided leads cause LBBB pattern, L) sided leads cause RBBB pattern
What are the main causes of general pacemaker dysfunction?
Pacemaker/Wires
- Battery issues/low
- Electrode displacement
- Lead fracture/inadequate contact
Person
- Electrolytes (esp hyperK)
- Ischaemia/infarction
- Fibrosis
- Meds ie flecainide, amiodarone
- Hypoxia, acidosis
What is the ideal number of amps for depolarisation of cardiac tissue?
30-40 amps
- 200j biphasic DC tends to deliver about 30amps to the myocardium
How should blood pressure be measured in someone with an LVAD?
- Manual sphygmomanometer and use a doppler ultrasound over the artery (radial, brachial etc) ie inflate high then when the doppler is heard is the MAP
- Invasive BP with arterial line
Normal MAP is usually 60-90mmHg in LVAD patients
What are the causes of haemodynamic collapse related to the LVAD in LVAD patients?
Direct LVAD
- Malposition of the LVAD
- Dysfunction of the LVAD (Kinking/blockage, Battery drainage)
- Incorrect pump speed
- Suck down event (can present as a dysrhythmia due to ventricular irritation)
Indirect LVAD
- bleeding due to acquired Von-Willebrands disease
- Acute haemolysis
- GI bleeding (causes AVMs and angiodysplasia)
- Device infection
- Thrombembolism from device
How does the management of dysrhythmias change when an LVAD is in situ?
Consider the possibility of a suction event aka suck down event
- inflow cannula contacting the septum causes irritation
- Most often caused by hypovolaemia, LVAD’s preload dependent
Give IV fluids
Decrease the RPM speed to lowest safe value
What are the most common bugs infecting LVAD’s?
Staph aureus
Enterococcus
Pseudomonas
