ICDs (edit) Flashcards
Heart attack
Blockage of Coronary arteries
The heart muscle is robbed of its vital blood supply and, if left untreated, will begin to die because it is not getting enough oxygen.
Cardiac arrest
Sudden cardiac arrest is the abrupt loss of heart function, breathing and consciousness.
The condition usually results from a problem with your heart’s electrical system, which disrupts your heart’s pumping action and stops blood flow to your body.
Relationship between cardiac arrest and heart attack
cardiac arrests in adults happen because of a heart attack. This is because a person who is having a heart attack may develop a dangerous heart rhythm, which can cause a cardiac arrest (I.e. heart stops pumping and breathing stops)
Brugada syndrome
characterized by incomplete right bundle-branch block and ST-segment elevations in the anterior precordial leads
Effects of ajmaline on electrophysiology
Ajmaline (class 1A) - sodium channel blocker
Main effect = longer refractory period and slower repolarisation
- lengthens the refractory period of the heart by blocking sodium ion channels = slower depolarisation = prolonged QR and longer action potential
Minimally blocks potassium channels = slower repolarization because it is harder for potassium to get out due to less unblocked channels = RS interval longer
Explain how antiarrhytmic drugs work
They work by blocking certain channels in cardiac cells
the blockage of channels means less ions can influx or leave cells thus affect how they act on conduction or repolarisation in the heart
Why can ajmaline be used to test for Brugada?
They both affect sodium channels - ajmaline prolongs refractory and widens QRS revealing brugada pattern
- The abnormal ECG pattern associated with Brugada is only seen spontaneously due to unknown triggers or after challenged by particular drugs
Why choose SICD over ICD?
No pacing indication
No ATP required
Save/preserve venous vasculature
Can ICDs be programmed unipolar?
No - risk of oversensing mypotentials negates it ability to be programmed unipolar regardless of lead issues
*dual chamber ICDs (atrial lead) also cannot be programmed unipolar due to risk of more A than V during V event = no therapies
What is the LV lead used for in CRT-D devices?
LV lead is used for pacing
*not sensing - only RV lead is used for sensing
Parameters to consider reprogramming in the occurrence of T wave oversensing
Sensitivity
sense polarity
T wave oversensing discrimination
Non-physiologic cycle lengths are
100-200ms
VT common in teens, near conduction system and hemodynamically stable (sometimes)
Fascicular VT
What Medtronic algorithm is at work here?
NCAP
What Medtronic algorithm is at work here?
NCAP
NSVT means
Device detected but terminated before charge end
VT Mon means
Detected in VT mon zone but not sustains long enough to be detected in VF or faster zone (if rates reach that zone)
Why does HCM cause arrhythmias and symptoms?
The abnormal development of the muscle walls of the heart can cause electrical pathways to become disrupted, resulting in irregular heart beats and arrhythmias
VT shocks
Cardiovert
VF shocks
Defibrillate
Patient has appropriate therapy for ventricular tachycardia, however patient was no fully unconscious when shock occurred and was traumatised. What considerations should be made when reprogramming therapies for optimisation?
Suitable therapy to successfully terminate arrhythmia
- ATP (most likely will not work in some conditions but appropriate to allow pain free therapy
- sometimes allow ATP to accelerate arrhythmia then patient is unconscious and can be shocked
What are the 4 types of shocks possible for ICDs?
Appropriate
Inappropriate
Unnecessary
Unsuccessful
Unwanted
ICD
What is sensing?
Process by which the ICD determines the prescience of a cardiac signal
“I see something”
ICD
What is detection?
Process by which ICD counts, measured and sorts the signals that it senses in order to identify an arrhythmia and make a therapy decision
“Here’s what I think”
What does an ICD need to determine if a tachyarrhythmia is present?
Definition of VT/VF rate = therapy zone
Rate = detection window
Duration = duration
Other clues = detection enhancements
Check again = last interval in zone
ATP settings are from which trial?
PainFree RX trial
*number of bursts: 1
Pulses per burst: 8
Couple interval: 88%
Burst cycle length: 88%
Minimum interval: 220ms
What criteria can be used to selection detection algorithms? - tachy rates
- What are the slowest tachycardia rates observed on the concurrent pharmacological regimen?
- determines high rate detection cutoff
- value chosen should be slightly below each ranch rate (10-20bpm)m
*monomorphic VT:
e.g. Tachycardia rate 180bpm -> rate boundary: 170bpm
Polymorphic monomorphic VT:
e.g. tachycardia rate 180bpm -> rate boundary 160bpm
What criteria can be used to selection detection algorithms? - sinus rates
What is the fastest attainable Sinus rate
If this is close to or above the minimum observable tachy rate, sudden onset should be used
What criteria can be used to selection detection algorithms? - exercise
Does the patient have exercise induced tachycardia?
If yes, Sustained rate duration may be programmed
Value chosen should be longer than patients max exercise duration
Does the patient have AF with RVR in addition to VT??
If yes, rate stability should be used to discriminate between AF and VT
