10. Pacing & CIEDs Flashcards
temporary cardiac pacing 4
transcutaneous
transesophageal
transvenous
epicardial
transcutaneous is preferred when?
an emergency
3 disadvantages to transcutaneous pacing
painful
least effective capture
ventricular only pacing
transcutaneous pacing CI
severe hypothermia
two placement options for transesophageal pacing
pill electrode swallowed
flexible catheter
flexible catheter can be inserted
what does transesophageal pacing pace? atria? ventricle?
atria
what current does transesophageal pacing require
high current
>20 mA
>20mA
advantage to transesophageal
no need for xray or cath lab
disadvantage to transesophageal
uncomfortable and requires sedation
when is transvenous pacing indicated?
stable or transcutaneous isnt working (inability to capture)
why does transvenous pacing take longer?
central line must be placed
pacing leads must be inserted through central line guided with balloon
how is transvenous pacing function controlled?
external pacemaker box
advantages to transvenous pacing 3
can place atrial and ventricular leads
more effective capture
doesnt require as much energy
what is the energy requirement for capture for transvenous pacing
1.5-3mA
disadvantages to transvenous pacing 2
more time consuming to establish (cant in emergency)
expert placement required
requires expert placement
epicardial pacing
common with cardiac surgery
leads are sewn into myocardium
controlled with external box
what do we pace at during cardiac surgery?
20mA
CIEDs
cardiovascular implantable electronic devices
what is a CIED
permanent pacemaker
placed into pocket by surgeon
what does a CIED consist of?
pulse generator (new SA node) pacing wires that have been inserted through subclavian vein into heart
what does the pulse generator act like
SA node
3 types of CIEDs
pacemaker
automated implantable cardioverter defibrillators (AICDs or ICDs)
chronic resynchronization therapy (CRT)
biventricular devices are typically
ICDs
two reasons for patients to receive a pacemaker
pace pts with slow heart rates
improve timing of atrial or ventricular beats in complete heart block
improve timing of atrial and ventricular beats for pts with complete heart block
single chamber
pacing lead in either RA or RV
single ventricle lead will pace
both ventricles
shocking coils allow
defibrillation
dual chamber
pacing lead in both RA and RV
what is an ICD?
CIED with specialized pacing lead placed in right ventricle that has a built in shocking coil
what can ICDs sense
arrythmias
heart contractions
intravascular ICD provide
pacing
synchronized cardioversion
antitachycardia pacing
defib
subcutaneous ICDs indication
only indicated for defib (cannot pace or sync cardioversion)
biventricular pacemakers or cardiac resynchronization therapy device
instead of the ventricles being paced by one lead they are paced by by two leads:
1 in RV
1 in coronary sinus to pace LV
what is the advantage of biventricular pacemakers?
2 ventricular leads improves ventricular synchrony in patients with a history of heart failure
5 intravascular CIED placement method
1- skin above subclavian is localized
2- a pouch under skin is created
3- pacing wires placed through subclav vein via fluoroscopy
4- pulse generator is programmed by pacemaker rep, then leads are attached
5- device is sewn underneath skin
what do you need to do if the device is an ICD
the shock function may need to be tested
when they test the ICD, give a small propofol bolus prior to shock
capture
cardiac cells responding to pacemaker stimulation
insert capture ecg
capture
pacing threshold
minimum current that capture is observed
transvenous/epicardial approach capture current
1.5-3mA
transcutaneous approach capture current
40-80mA
why do we want to avoid high voltages?
cause discomfort
incr risk of myocardial damage
myocardial damage
pacing threshold
the current that you found capture
maintenance threshold
10% higher than pacing threshold to decrease chance of losing capture
sensitivity threshold
how sensitive the pacemaker is to sensing electrical activity in heart
if the sensitivity is too high?
not pace as much as it should
if the sensitivity is too low?
it may pace when it is not supposed to
intrinsic heart rate
HR set by SA node
60-100bpm
paced HR
HR that comes from battery operated pacemaker
~60bpm
how can you tell on ecg if the beat is paced?
there is a pacer spike prior to a p wave or qrs complex
will pacemaker spikes automatically come up on the ecg?
no you must enable the pacemaker setting on the monitor
insert pacer spike ecg
pacer spike
two potential sources of heart beat in pt with pacemaker
SA node (intrinsic HR)
pacemaker (paced HR)
pacemaker
why is it dangerous to have two potential sources of heart beats?
if they both go off it can be mistimed and lead to r-on-t phenonmenon and lead to vfib/vtach
insert R on T phenomenon ecg
R on T phenomenon
Insert R on T Vfib
R on T leading to Vfib
what is demand mode
a pacing mode that makes it so that only one source (SA or pacemaker) is providing current to the heart
demand mode senses
the intrinsic heart rate
in demand mode, is the pacer always pacing
no
pacer only paces if needed
what prevents mistimed beats and arrhythmias?
sensing by the pacemaker in demand mode
when the pacemaker can sense it is
in demand mode
in demand mode the pacemaker will
stop pacing when they can sense
start pacing when they cannot sense
if the intrinsic rate is faster than the paced rate, the pacemaker will?
be suppressed
if the paced rate is faster than the intrinsic rate then the intrinsic rate will
be suppressed
effect of cautery on pacemaker
pacemakers sense surgical cautery and interpret it as electrical activity of the heart
will pacemakers pace during cautery?
nope
pacemaker dependent
whenever a patient is reliant on their pacemaker to have a normal cardiac output
asynchronous mode
pacemaker cannot sense anything and they start pacing constantly
asynchronous pacers will pace
constantly regardless of intrinsic rate
advantage of asynchronous mode
pacemaker cannot sense cautery
pacemaker will not stop during cautery
problem with asynchronous mode
it is possible for the two sources to be simultaneously pacing
can lead to r-on-t phenomenon and vfib
when is asynchonous mode safe?
when the intrinsic rate is slower than the paced rate
pacemakers should only be placed in asynchonous mode if
pacing rate is high
the pt’s intrinsic HR is slow
patients intrinsic HR is slow
pacing rate in asynchronous mode
programmed for pace rate to increase to 80-100 bpm
before putting in asynchronous mode what should the anesthetist check?
confirm intrinsic rate is slower than asynchronous rate
consider beta blocker
when could asynchronous mode be necessary?
pacemaker dependent pt is experiencing profound cautery induced bradycardia
how to convert pacemaker to asynchronous mode
place magnet over it
or
pacemaker rep can reprogram prior to surgery
why is rate modulation programed into pacemaker?
the pacemaker can sense incr movement or minute ventilation and incr the rate to provide higher CO during exercise
antitachycardia pacing (ATP)
senses tachycardia and paces faster than intrinsic rate to suppress it
what rhythms can ATP be effective for
afib
aflutter
svt
monomorphic vtach
if several attempts at ATP prove ineffective what will the pacemaker do?
shock the heart
indications for pacemaker 5
sinus brady sick sinus syndrome (malfunctioning SA node) 3rd degree av block mobitz type II heart block afib with slow ventricular response
what pacemaker should be used for chronic sinus brady or SSS
atrial pacing
what type of pacemaker should be used for afib with slow ventricular response?
ventricular because atrial wouldnt work because it has constant electrical activity
pacing spike before QRS is what type of pacing
ventricular pacing
where is the ventricular lead placed
close to septum and causes left and right ventricles to contract
Leadless right ventricular pacemaker location
RV via femoral access
Leadless pacemaker advantages
decr risk of:
- lead infection
- vascular thrombosis
- lead dislodgement
- lead fracture
leadless pacemaker disadvantages
no defib
does not respond to magnets
what type of pacemaker should be used for 3rd degree av block?
dual chamber
atrial lead senses when there is activity and signals for ventricular pace
how does dual chamber pacemaker fix complete heart block 2
atrial lead senses when atria contract
ventricular leads programmed to pace
ventricular lead pace 120-200 msec after atria contracts
when dos the ventricular lead pace in dual chamber for heart block?
120-200 msec after every atrial contraction
newer pacemaker for complete heart block
single chamber pacemaker where it has sensing portion in RA and the pacing portion in the RV
insert DC pacemaker w/DC pacing
DC pacemaker w/DC pacing
DC pacemaker w/both atrial and ventricular pacing spikes
patient has both:
SA node dysfunction
slow AV conduction
DC pacemaker w/atrial pacing
DC pacemaker w/atrial pacing
DC pacemaker w/atrial pacing
SA node is slow
AV node is normal
DC pacemaker w/ventricular pacing
DC pacemaker w/ventricular pacing
DC pacemaker w/ventricular pacing
SA node is normal
AV conduction is slow
ventricular only pacing w/o P waves
underlying afib
ventricular only pacing w/p waves
underlying complete heart block
DC pacemaker w/normal ECG
SA node is normal
AV node conduction is normal
will you see a atrial pacing spike with the single chamber pacemaker for complete heart block?
no
biventricular pacemakers are AKA
cardiac resynchronization therapy (CRT)
what do biventricular pacemakers have in addition to a normal RV lead
LV lead inserted via coronary sinus
advantage of having a lead in both ventricles in biventricular pacemakers
improves timing of ventricular beats
incr SV/CO
decr myocardial O2 demand
what does an ICD have?
specialized ventricular pacing lead that has a built in shocking coil that senses and shocks tachyarrhythmias
who are ICDs usually placed in?
CHF pts bc they are more prone to tachyarrhythmias
what are ICDs capable of?
pacing and defibrillating
traditional ICD
RV lead capable of pacing and shocking
S-ICD
CANNOT pace
only indicated for defib
only defibtrillate
advantage to S-ICD
no need to replace fibrosed leads
just as effective as transvenous
disadvantages to S-ICD
not indicated in pts who require antibrady pacing, CRT, or antitachycardia pacing
higher energy requirements
not for ventricular arrhythmias at rates lower than 170bpm
why are ICDs dangerous
can be inappropriately triggererd to shock whenever cautery is used
an ICD thinks cautery is
vfib
it will defibrillate
what are ICDs programmed energy to shock
15-35 J
two ways to prevent accidental shock from an ICD during surgery
1 disable the shock function of the ICD (programmer or magnet over the ICD)
2 keep electrical current away from the ICD
how many cm should the grounding pad be placed away from ICD
15cm
what are alternatives to unipolar cautery
bipolar or harmonic scalpel
harmonic scalpel
cuts via vibration and seals tissue with protein denaturation
advantages to harmonic scalpel
cuts thicker tissue than bovie
less smoke
less thermal damage
disadvantages to harmonic scalpel
takes longer to cut and coagulate tissue
can only coagulate as it cuts
can only coagulate as it cuts
magnet on ICD does what
diable the shock function only
does the magnet on ICD convert the pacing to asynchronous mode?
no
can cautery induced bradycardia occur with magnet on ICD?
yes
how to prevent cautery induced bradycardia during surgery for pacemaker dependent pts with ICD?
ask pacemaker rep to reprogram ICD before surgery to allow it to become asynchronous with magnet placement
when should the shock function of an ICD be disabled?
if surgeon plans on using cautyer
if surgical site is above the umbilicus
pacemaker dependent patient has a magnet placed over their ICD what will happen during cautery
no shock, possible brady or asystole
pacemaker interrogation
15min procedure that checks the function and battery life of pacemaker
waves wand and connects to computer
pacemaker checks are
scheduled at regular intervals over the pts life
recommended by doctor prior to elective procedure
how often should pacemaker be checked
every year
how often should ICDs be checked?
every 6mo
preop management of CIED
obtain/document results of last pacemaker interrogation and intraoperative recommendations by calling number on card in wallet or bracelet
9 things for anesthesia to know in preop CIED pts
1 type of device (pacemaker vs ICD) 2 programmability of device 3 underlying rhythm 4 pacemaker dependent? 5 does it have rate modulation 6 pacemaker capture effectively 7 what is magnet response? 8 adequate battery life 9 manufacturers perioperative recommendations?
normal battery life
7-10 years
adequate battery life for surgery
> 3-6mo
intraoperative management supplies and drugs CEID
external pacemaker
magnet
atropine
epi
postop management CEID
all devices should be interrogated or reprogrammed to original function after surgery
not discharged until interrogated
study;s have shown that magnet application over ICD have not always:
suspended antitachyarrythmic function
produce asynch pacing for demand pacemaker
produce safe asynch pacing
a male pt has a regular demand pacemaker w/the following ECG
is he pacemaker dependent?
No
a male pt has a regular demand pacemaker w/the following ECG
what is the effect of cautery on HR?
no change
a male pt has a regular demand pacemaker w/the following ECG
what will magnet placement do?
change to asynchronous mode
incr pacing to 80-100 bpm
a male pt has a regular demand pacemaker w/the following ECG
should we place a magnet?
no
this pt has an intravascular ICD with the following ECG. Cautery is planned.
What is magnet placement most likely to do?
disable shock
this pt has an intravascular ICD with the following ECG. Cautery is planned.
should a magnet be placed on this patient?
yes
a male pt has a regular demand pacemaker and he goes asystolic when cautery is used. How should he be managed during surgery?
place a magnet
a female pt w/intravascular ICD is pacemaker depended. Shock function was disabled by pacer rep prior to surgery. During surgery she becomes asystolic when cautery is used. How should she be managed?
switch to bipolar cautyer
or
reprogram ICD
a male pt has a regular demand pacemaker and his ECG is showing all P waves are preceded by pacing spikes. If cautery is not being used, how do you explain the ECG?
perhaps the rate modulation was not disabled?
we expect constant HR
first letter chamber classification
what chambers have pacing leads
second letter chamber classification
what chambers can sense electrical activity
third letter chamber classification
how pacemaker responds after it senses electrical activity
fourth letter chamber classification
programmability
fifth letter chamber classification
antitachyarrhythmia function
options for first letter
a= atria v= ventricle d= dual
options for second letter
a= atria v= ventricle d= dual o= none
what does it mean when the second pacemaker letter is O?
it is in asynchronous mode
options for third letter
I= inhibits T= triggered D= Dual (t+i) O= none
third letter I
inhibit itseld from pacing
(demand mode)
third letter T
triggered to pace
third letter D
dual = pacemaker is triggered and inhibited
when can the pacemaker be triggered and inhibited
complete heart block
- atrial lead inhibits iself from pacing
- atrial lead triggers ventricular to pace
third letter O
if the 2nd letter is O the 3rd letter will also be O
indicates asynchronous mode
pacemaker code for pt with sinus brady
AAI
pacemaker code for pt with slow afib/aflutter
VVI
pacemaker code for pt with complete heart block
DDD
right ventricular pacemaker code for pt with complete heart block
VDD
pacemaker code for pt with sinus brady and magnet on pacemaker
AOO
AAI
single lead in RA for pts
demand pacing
AAI indications
sinus brady
SSS
AOO
asynchronous pacing from RA activated by magnet
VVI
single lead in RV
demand pacing
VVI indication
a fib
VOO
asynchronous pacing with the lead in the RV activated by magnet
DDD
leads in RA and RV for pts with complete heart block
DOO
asynchonous pacing with leads in RA and RV activated by magnet
DOO RV is programmed to pace when
120-200 msec after each atrial beat
VDD
specialized lead in RV that has a sensing portion in the RA
VDD indication
complete heart block with normal functioning SA node
can pt with pacemaker have MRI
NO
CT scan and pacemaker
some ICDs receive interference
are ICDs or pacemakers more sensitive to radiation therapy?
ICDs
what to do if pt with ICD and radiation therapy
shielded as much as possible and moved if it lies directly in radiation field
radiofrequency ablation
waves to ablate areas of the heart/terminate arrhythmias
acceptable with certain precautions
emergency defibrillation for pt with pacemaker
place the defib pads away from pacemaker
TENS
transcutaneous electrical nerve stimulation
used to relieve acute or chronic pain
TENS and CIEDs
reported to interfere with ICDs to cause inappropriate shock
cautioned about use
ECT
electroconculsive therapy
transcutaneous electrodes placed on head to induce a tonic clonic seizure
treat depressio
how often is ECT performed
twice weekly for usually 3-4 weeks
what is too short or too long of seizure?
too short: < 10s
too long: > 120s
>120 sec
which is more important the length or seizure or current delivered?
current delivered
cardiovascular effects of ECT
initial parasympathetic discharge (brady and hypotension) then sympathetic response
how long does initial parasympathetic discharge last in ECT?
10-15 s
when does secondary sympathetic response peak in ECT?
3-5 mins
cerebral effects of ECT
incr cerebral oxygen consumption
incr blood flow
incr ICP
what are the more popular induction agents for ECT
brevital or etomidate
methohexital
pro convulsant
does not change duration
blunt sympathetic response
etomidate
longest seizure duration
does not blunt the sympathetic response
propofol
decreases seizure duration
does blunt the sympathetic response
ketamine
longer seizure duration
incr ICP
ICP elevates
airway management for ECT
usually not ETT unless indicated
mask ventilation
hyperventilate to lower the threshold for seizure and prolong the duration
neuromuscular blocking agents and ECT
reduce muscular convulsions and decrease risk of serious injury (sux most common)
CIED implications for ECT 4
1 skeletal muscle potentials during seizure may trigger pacemaker
2 regular demand should be asynchronous
3 shock function of ICD deactivated
4 risks are low bc small amounts of electricity reach device
ESWL
extracorporeal wave lithotripsy
transcutaneous ultrasonic shock waves breaks up kidney or ureteric stones
synchronized litho shocks
triggered by the R wave
delivered in refractory period
advantage to synchronized shock
carries lower risk of PVCs and arrhythmias
disadvantage to synchronized shock
procedure is slower
non synchronized litho shocks
shocks delivered at specific rate
advantage of non synchronized litho shock
procedure is faster
disadvantage to non synchronized litho shock
more likely to cause PVCs or arrhythmias
ESWL and CIEDs
may interpret shocks same as cautery
magnets should be placed on ICD pt or pacemaker dependent pt
what can happen in atrially paced pts with ESWL?
the synchronized shock can read the atrial pace as the R wave and deliver a shock prior to the R wave causing arrhythmia
atrially paced CIEDs during ESWL
avoid synchronized shocks
regular demand pacemakers during ESWL
place in asynchronous mode if pt is pacemaker dependent
ICD during ESWL
disable shock function