June 15, 2025 • 23 mins
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This episode features a deep dive into Anaesthetic Management of Patients with Cardiac Devices based on several materials.
Listen for a clear, concise overview powered by Google's NotebookLM AI, perfect for exam prep or clinical refreshers.
Let’s dive deep.
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Episode Transcript
Available transcripts are automatically generated. Complete accuracy is not guaranteed.
(00:00):
OK, let's dive in. We are exploring a world of
truly life saving technology today.
Cardiac implantable electronic devices, you know, pacemakers,
defibrillators, these little machines are becoming incredibly
common. They really are, and they're
allowing people to live much fuller lives.
Exactly. But that also means we're seeing
(00:22):
more and more patients who rely on these devices needing other
kinds of surgery. Right.
And that has a whole new layer of complexity, doesn't it, For
managing their care during thoseprocedures?
Absolutely. So our deep dive today is all
about navigating that complexity, the really crucial
things to consider when managingpatients with these devices
during surgery. Yeah.
(00:42):
And we've got some great sourceshere, a really interesting large
scale study from Vienna, some practical guides to.
It's a good mix. It is and it helps us understand
the and you know how to handle the potential challenges.
It's pretty amazing how far thisfield has come.
I mean, our sources remind us this whole thing really kicked
off back in 1958. Wow. 50.
Yeah, the very first fully implantable pacemaker insertion
(01:05):
done under general anaesthesia, interestingly enough.
That's incredible. From just one patient then to
millions now. Quite a leap.
It really is. All right, so before we get into
the the operating room challenges, let's just make sure
everyone's on the same page. What exactly are these devices?
What are the main types we should know about?
Well, the sources mostly focus on two key types, pacemakers, or
(01:27):
PMS and implantable cardioverterdefibrillators, Icds.
Pacemakers fundamentally are there to help a heartbeat
speeding too slowly. They send out little electrical
impulses to keep the rhythm going at a safe rate.
Right, speeding things up if needed.
Exactly. Then you have IC D's.
Their main job is to detect and stop dangerously fast,
(01:49):
potentially lethal heart rhythmslike Vt or V fib.
How do they stop? Them usually by delivering an
electrical shock. But this is important.
ICD's can also pace the heart. They have pacemaker functions
built in for when the heart is too slow.
Ah OK, so PMS for slow rhythms, ICD's for fast rhythms.
But ICD's can also do the slow rhythm job.
(02:10):
Got it. And what are the actual physical
parts of one of these things? You can think of it as having
three main components. First, there's the pulse
generator. That's the device itself, the
brain if you like, containing the battery and all of the
complex circuitry. And these have shrunk
dramatically, right? Unbelievably, the sources note
they started around what, 120 grammes back in the early days?
(02:31):
Wow. And now they can be as small as
like 9 grammes. It's incredible miniaturisation.
Seriously. Like fitting a whole computer
system into something lighter than a than a standard battery?
Yeah, that's amazing engineering.
It really is then connected to the generator, you have the
leads. The wires.
Yep, insulated wires. They run from the generator,
which is usually implanted up inthe chest area, down into the
(02:53):
heart, typically threaded through a vein, and then right
at the tips of those leads are the electrodes.
These are the crucial contact points.
They deliver the electrical pulses to the heart muscle when
pacing is needed. And they listen to, right?
Exactly. They also sense or listen for
the heart's own intrinsic electrical activity.
That sensing part is key to how they operate.
(03:15):
OK, so they send signals and they listen for the heart's own
signals. Why does someone actually get
one implanted? What are the main reasons?
It usually boils down to problems with the heart's
electrical system. Oh, for pacemakers, it's often
things like symptomatic bradycardia, a heart rate so
slow it causes fainting or severe dizziness.
Right? Or certain types of heart block
where the signals just aren't getting through properly.
(03:37):
For Icds, it's typically for patients who are at high risk of
sudden cardiac death because of dangerous ventricular
arrhythmias. They've either survived 1
already or they have a heart condition that puts them at high
risk. And how does the device figure
out when to step in and pace, orwhen to just hang back and
listen? Is there like a setting?
There is, absolutely. It follows specific programmed
(04:00):
instructions, and these are often described using a special
code. It's called the NBG code.
NBG. Yeah, named after the groups
that standardised it. It's often presented as A5
letter code, but honestly in day-to-day practise you most
commonly see devices programmed using just the first 3 letters
and. What do those letters tell you?
Each letter signifies something specific.
(04:20):
The 1st letter tells you which heart chamber is paste.
The second tells you which chamber is sensed, and the third
tells you how the device responds when it senses the
hearts own beat. OK, so let's take an example.
What about VVII? Hear that one mentioned a lot.
VVI is super common, so the first V means it paces the
ventricle, the second V means itsenses the ventricle, and the
(04:42):
3rd letter I stands for inhibited.
That means its response when it senses a natural heartbeat in
the ventricle is to inhibit its own pacing pulse.
So it holds back if the heart isdoing its own thing.
Precisely. It listens, and if it doesn't
hear a natural beat within a certain time frame that it
paces, otherwise it stays quiet.That makes sense.
(05:02):
Blates its turn. And you mentioned VOO earlier as
maybe a default or temporary mode.
How's that different? Right VOO is quite different.
First V is paste in the ventricle, but the second letter
is O, meaning it senses in neither chamber or sensing is
off. No sensing none.
And the third O means its response to sensing is also O or
(05:24):
none. So basically it just paces the
ventricle at a set fixed rate. It completely ignores whatever
the hearts own electrical activity might be doing.
Less sophisticated. It is in a way.
It's called an asynchronous mode.
But that lack of sensing that just pacing regardless, can
actually be really important, even necessary in certain
(05:45):
situations like during surgery with potential interference.
OK. So that leads us right into the
operating room. You've got this patient, they
have the sophisticated little device, and you bring them into
an environment full of, you know, monitors, electrical
equipment and especially surgical tools that use
electricity. What's the number one headache
for these devices in the OR? The absolute biggest concern,
(06:06):
the one we really need to focus on, is electromagnetic
interference. EMI.
Yeah, basically external electrical or magnetic fields
that can seriously mess with howthe device is supposed to work.
And what's the most common source of EMI in the OR is it
the the electric cautery? Spot on Electrosurgery, what
most people call the Bovie and the sources are clear.
(06:27):
Monopolar electric cautery is much more likely to cause
problems than bipolar. Why is that?
It's all about the path the electrical current takes.
With bipolar, the current just flows between the two tips of
the instrument. It's very localised, very
contained. Right, like tiny tweezers.
Exactly. But with monopolar, the current
goes from the active tip throughthe patient's body all the way
(06:48):
to a grounding pad stuck somewhere else on their skin.
So a much bigger circuit throughthe patient.
A much bigger, less predictable circuit, and that creates a much
larger electromagnetic field that the pacemaker or ICD is
more likely to pick up his noise.
OK, so here's the really crucialpart.
What can actually happen if thatEMI does interfere with the
(07:09):
device? What are the dangers the sources
talk about? The effects can be pretty scary
honestly. One of the most critical is
inhibition of pacing. Inhibition, meaning it stops
pacing. Yes, the device senses the EMI
noise, mistakes it for a naturalheartbeat.
We call that over sensing and soit holds back its pacing pulse
just like it's programmed to do in VVI mode for example.
(07:31):
So if the patient needs that pacing.
Exactly. If the patient is pacing
dependent, meaning their own heart rhythm isn't adequate,
this in addition can cause theirheart rate to drop dangerously
low, severe bradycardia or even a systol.
No heartbeat at all. Wow, so the interference
literally trips the device into stopping, potentially stopping
the patient's heart. That's incredible.
(07:52):
Notably serious. What else?
Well, on the flip side, EMI can sometimes cause inappropriate
pacing or shocks. How so?
Some devices have these sensors,called rate responsive sensors,
that are meant to increase the pacing rate when the patient is
active, like sensing vibration or changes in breathing EMI can
sometimes falsely trigger these sensors, leading to leading to
the pacemaker suddenly pacing way too fast, causing
(08:15):
tachycardia when the patient doesn't need it.
And for ICDS it's even worse. The device might misinterpret
the EMI noise as a life threatening arrhythmia like V
fib and then it delivers a powerful, completely unnecessary
and very painful shock to the patient.
Yikes, getting shocked inappropriately during surgery.
I can't even imagine. Definitely something we have to
(08:37):
prevent, and it's not just aboutconfusing the device's software.
Strong EMI can potentially causeactual physical.
Damage. Damage to the device itself.
Or the leads, or even the heart tissue.
The electrical energy can generate heat.
This could potentially burn the heart tissue right where the
electrode touches it, or damage the insulation on the leads, or
even harm the circuitry inside the generator itself.
(08:59):
It could lead to temporary or even permanent malfunction.
So it can stop pacing, pace too fast, shock when it shouldn't,
or just break. That's quite a list.
It is, and there's one more thing.
Mode resetting really strong EMIcan sometimes overwhelm the
device's logic and cause it to to revert to a sort of factory
default or backup mode. Like a safe mode?
(09:19):
Kind of. Often it resets to something
basic like VDI or VOO. Now these modes are usually safe
in the short term, but they might not be the best mode for
that particular patient. And if you weren't expecting it,
you might even think the batterydied or something.
OK, so mainly the boovie. Are there other things in the OR
or hospital environment mentioned in the sources that
can cause interference? Yeah, less commonly problematic
(09:40):
in routine surgery, but still worth knowing.
Things like the guide wires usedfor putting in central lines.
If they haven't to touch or get very close to the device leads
in the heart, that mechanical contact can sometimes be
misinterpreted as heart signals.Causing inhibition or shocks
again. Potentially, yeah, especially
inappropriate ICD shocks or pacing inhibition.
(10:02):
MRI is obviously a huge source of EMI, which is why we have MRI
conditional versus MRI unsafe devices, a whole separate topic
really, right? And even some RFID tags, the
radio frequency ID things used for tracking equipment or
supplies, could theoretically interfere if they're held right
up against the device. And didn't I see something about
muscles like muscle contractions?
(10:23):
That's a more subtle one, but yes, strong skeletal muscle
twitches are contractions. Sometimes you see this with
certain muscle relaxants like sexy little choline used in
anaesthesia can generate tiny electrical signals called
myopotentials. And the pacemaker might pick
those up. A very sensitive pacemaker might
mistake those muscle signals forheartbeats and briefly inhibit
(10:45):
pacing. It's usually just a fleeting
effect, but it's possible. OK, so it's clear that bringing
a patient with one of these devices into surgery isn't
straightforward. It needs a really careful
thought out plan. How do the teams actually manage
this safely it? Absolutely has to be a planned
team effort. A multidisciplinary approach is
(11:05):
key. You need the cardiologist or the
electrophysiologist who knows the device, the device
technician, the surgeon and the anaesthesia team all talking to
each other. Communication is.
Vital. Totally.
Everyone needs to be on the samepage.
All right, let's break down the process.
What happens before the procedure, the prep phase?
What information is critical to gather?
First, the absolute basics. Confirm the patient has a
(11:27):
device. Sounds obvious, but you need to
ask. Look for the scar, feel for the
generator under the skin. OK, then you need the details.
What kind of device is it? Pacemaker or ICD?
Who made it? Different manufacturers have
different features, different magnet responses.
And critically, why was it implanted?
What's the underlying heart condition?
(11:47):
I guess the most important question is are they dependent
on it? Exactly.
That's probably the single most crucial piece of information.
Is the patient pacing dependent?Do they rely on that device for
a safe heart rhythm, or do they have a decent underlying rhythm
of their own? How do you figure that out?
Several ways. You look at their history.
Did they get the pacemaker because they were fainting from
(12:08):
a slow heart rate? Did they have a procedure called
an AV node ablation which essentially makes them
dependent? Or ideally you look at the data
from their last device. Check.
The interrogation report, yes. That report can often tell you
if the device is pacing 100% of the time, suggesting dependence,
or if the patient has their own rhythm kicking in frequently.
And how do you get that report or other device info?
(12:32):
The patient usually carries an ID card with basic info.
Getting the actual interrogationreport is best called the
cardiologist's office or the device clinic.
Sometimes the chest X-ray can help identify the device type.
ICD leads look thicker because they have Defibrillation coils
and check lead position. Is it standard practise to get
the device interrogated right before surgery?
(12:54):
It's highly recommended, especially if you anticipate
using monopolar cautery or if the surgery is near the device.
Getting it checked within say the last three, six months or
even the morning of surgery gives you vital up to date info
on battery life, lead function and the current settings.
And based on that check and the plan surgery, you might actually
change the settings temporarily.Yes, that's often necessary.
(13:17):
Temporary reprogramming is a keypart of the plan.
What kind of changes? OK, so if your patient is pacing
dependent and the surgeon is going to be using monopolar
cautery, especially anywhere above the belly button where the
current path is likely to cross near the device.
Right. Higher risk of interference?
Then you absolutely need to reprogram the pacemaker to an
asynchronous mode like VOO or Doo if it's a dual chamber
(13:41):
device. The mode that just paces
regardless of sensing. Exactly, that ensures the pacing
continues uninterrupted even if there's a tonne of EMI noise.
You're basically telling it ignore everything, just keep
pacing at this rate. Makes sense.
What else might you change? You generally want to turn off
any rate responsive features. Remember those sensors that
adjust pacing rate based on activity?
Yeah, well, things like surgicalretractors vibrating or even the
(14:05):
patient being mechanically ventilated can falsely trigger
those sensors and cause unwantedrapid pacing.
So turn that off. And crucially for ICDS, if
there's the significant risk of EMI, you must temporarily
suspend the anti tachyrhythmia functions.
Meaning turn off the shocking capability.
Yes, turn off the detection and treatment of tachycardia and
(14:26):
fibrillation. You absolutely do not want the
movie noise to trick the ICD into delivering an inappropriate
shock during surgery. That sounds critical, and you
have to do that in a safe place,right?
Absolutely. You only disable shocks in a
monitored setting where you haveexternal Defibrillation
immediately available, just in case the patient actually does
have a dangerous arrhythmia while the ICD function is off.
(14:47):
What about magnets? You hear about slapping a magnet
on the device? Is that a shortcut?
The magnet, Yeah, it's useful. Useful sometimes, but it's
definitely not a universal fix or a substitute for proper
reprogramming if EMI is expected.
How does it work? It depends on the device type
and manufacturer. For most pacemakers, applying
the correct magnet will switch it to an asynchronous pacing
(15:09):
mode like VOO or DO, but often at a specific magnet rate, which
might not be ideal. OK, so it's forces pacing for
PMS, what about ICDS? For most ICDS, putting a magnet
on suspends the shock therapy. It stops it from delivering
shocks. But does it change the pacing?
Generally no. This is the key point people
misunderstand. The magnet usually doesn't
change the pacing mode of an ICD.
(15:31):
So even with the magnet on, the ICD is pacing function can still
be inhibited by EMI if it's in amode like VVI.
So magnet on an ICD shocks off, but pacing might still stop due
to interference. Exactly.
So it's useful for quickly disabling shocks in an
emergency, maybe, but if you need reliable asynchronous
pacing during EMI, reprogrammingis the way to go.
(15:54):
Magnet response isn't totally standardised either.
Good to know. Not a magic wand.
OK, so planning done, reprogramming done.
Now we're during the procedure. Vigilance is key, you said.
What does that look like? Continuous monitoring is
baseline ECG constantly watched pulse oximetry, looking at the
waveform 2 For a peripheral perfusion blood pressure
(16:15):
monitoring, you need eyes on therhythm strip nonstop.
And backups ready. Absolutely.
External defibrillator pads should ideally be placed on the
patient prophylactically if you've turned off their ICD
function or if they're high risk.
At the very least, the machine and pads must be in the room,
plugged in, ready to go instantly.
Transcutaneous pacing capabilities should also be
immediately available. And what about the surgical
(16:36):
side? How can the team using the
cautery minimise the risk? There are definite techniques.
First, try to position the grounding pads so the current
path from the active movie tip to the pad doesn't run through
or near the pulse generator and leads.
Keep the current away from the device, right?
Also, avoid just waving the active electrode around near the
generator pocket, right? Use the lowest possible energy
(16:58):
setting on the cautery unit. That still does the job
effectively. And crucially, use it in short
intermittent bursts, not long continuous activations.
Like quick taps rather than leaning on the pedal.
Exactly. Give the device moments to
recover and function normally between bursts.
And of course, if bipolar cautery or an ultrasonic scalpel
can achieve the surgical goal, use those instead.
(17:21):
They generate much less EMI. Much safer alternatives if
practical. Definitely preferred when
possible. And what if, despite all the
best planning and precautions, you do see something weird
happening on the monitor? Like the heart rate suddenly
drops or the pacing spikes disappear.
If you suspect device interference or malfunction, the
rule is clear. Stop the source of interference
(17:42):
immediately. Usually that means stop the
electrocautery. Pause surgery.
Pause whatever's causing the suspected EMI.
Assess the patient, assess the rhythm, figure out what's going
on. You don't proceed until the
issue is understood and managed.Maybe you need to reposition the
grounding pad, switch to bipolar, or confirm device
settings. Haven't reset safety first.
(18:02):
Absolutely. OK, let's talk about outcomes.
That big Vienna study you mentioned looked specifically at
procedures where CIS were being implanted.
A bit different from managing them during other surgeries, but
it still gives us a window into the risks these patients carry,
right? It's as it looked at over 15,000
patients getting PMS or Icds. They track things like needing
(18:22):
CPR during the implant procedureitself and also mortality within
30 days and. What did they find?
Were complications common? The rates were relatively low.
Thankfully, meeting CPR during the actual implant happened in
only .39% of cases. Less than half a percent.
Right. And the 30 day mortality rate
was .8%. Now the authors made a point
about that .8%. They argued that while it might
(18:44):
sound a bit high for what's often an elective procedure,
their analysis suggested it wasn't really due to the implant
procedure itself, but more reflected the severe underlying
health problems of the patients getting the devices.
They compared it favourably to mortality rates seen after other
major surgeries in similarly frail populations.
OK. So the patients are often quite
(19:05):
sick to begin with. Did the study identify specific
things that put patients at higher risk for those bad
outcomes? Yes, a few key things stood out.
A major 1 was acute heart failure or AHF.
Having AHF at the time of the implant was a significant
independent predictor for both needing CPR during the procedure
and dying within 30 days. That really underscores the
(19:27):
fragility of those patients. It does.
Another interesting finding was about the anaesthetic technique
used for the implant. Oh, how did that matter?
Compared to just having local anaesthesia with standby
monitoring, using either sedation or full general
anaesthesia was linked to a significantly higher chance of
needing CPR during the implant. Wow, any idea why that they say?
The study showed the association, but didn't deeply
(19:50):
explore the why. It could be that patients
needing GA or deeper sedation were inherently sicker, or
perhaps respiratory effects of sedation played a role.
It's an interesting correlation from that specific implant
setting. What else?
Increased risk. For 30 day mortality, older age,
especially over 86, having a history of fainting before the
implant or having had CPR previously were all risk
(20:13):
factors. And unsurprisingly, other heart
problems like coronary artery disease or cardiomyopathy,
meeting blood pressure support with vasopressors or having low
oxygen levels also increase the risk of dying within 30 days.
Makes sense. Those are markers of sicker
patients. Was there any good news in the
data? Any trends?
Yes, actually a very positive finding was that the risk of
(20:35):
needing CPR during the implant procedure significantly
decreased over the long study period, which ran from 1997 to
2019. Well, that's.
Great. Yeah.
It suggests a real learning curve or improvements in the
technology, the techniques, maybe team experience.
Over those couple of decades, practise got safer.
That's very encouraging to hear.OK, So the procedures done, the
patient's heading to recovery, What's critical in the after the
(20:58):
procedure phase to make sure everything's OK and they go home
safely? OST U management is just as
vital. You can't relax yet.
Continuous cardiac monitoring watching their heart rate and
rhythm needs to continue in the recovery area or ICU.
And Kee the Backus nearby. Absolutely.
That external pacing and Defibrillation equipment should
remain immediately available until you're sure the patient is
(21:20):
stable and, crucially, until thedevice has been checked in any
temporary settings have been putback to normal.
So checking the device again afterwards is important.
Post operative device interrogation is key.
The source is strongly recommended, especially in
certain situations. Like when?
Definitely if any settings were changed before or during the
surgery. If it was an emergency operation
(21:42):
where you didn't get a full pre op assessment.
If there's any suspicion that the device might have been
affected, like if there was a lot of EMI used nearby, or if
the patient had large fluid shifts, or if the ICD shocks
were turned off. What does that post op check
tell you? It confirms the device is still
working properly, cheques the battery status again, make sure
the leads are sensing and pacingcorrectly, and it's your chance
(22:03):
to restore the patient's optimalpermanent settings.
And when should those permanent settings be put back?
Can they go home with the temporary?
Ones no. The standard permanent settings
should ideally be restored before the patient leaves a
monitored setting like pay CU orthe hospital ward.
If for some reason an interrogation can't happen right
away, postdoc. The recommendation is to get it
(22:23):
done within 30 days. Got it.
This has been a really comprehensive look.
It's definitely clear that managing these patients requires
a lot more than just, you know, standard surgical care.
It really highlights how sophisticated medical technology
requires equally sophisticated planning, teamwork and vigilance
from the human side. So if you had to boil it down,
(22:44):
what's the absolute key takeawayfor our listeners about managing
patients with CI ES around the time of surgery?
I think it comes down to a few core principles.
First, understand the specific device your patient has and and
why they have it. Second, anticipate the potential
interactions, especially EMI from electric artery.
Third, meticulous planning and risk assessment beforehand. 4th,
(23:08):
seamless communication among everyone involved.
Anaesthesia, surgery, cardiology, device techs, and
finally continuous careful monitoring throughout the entire
perioperative journey. And being ready to act if
something goes wrong. Exactly.
The technology is amazing, but safe care still relies on those
fundamental clinical skills, assessment, preparation and
(23:29):
readiness to intervene. It's been fascinating, so here's
a final thought for you, the listener to Mull over as this
CIE technology keeps getting smarter and smaller.
We're talking wireless monitoring, maybe even sensors
built into the leads that track hemodynamics in real time.
How might that change the game? Will the need for direct human
cheques and interventions like reprogramming or post op cheques
lessen? Or will it just shift how
(23:50):
healthcare teams need to coordinate and use that data in
the future? Something to really think about.
OK, let's dive in. We are exploring a world of
truly life saving technology today.
Cardiac implantable electronic devices, you know, pacemakers,
defibrillators, these little machines are becoming incredibly
common. They really are, and they're
allowing people to live much fuller lives.
Exactly. But that also means we're seeing
(00:22):
more and more patients who rely on these devices needing other
kinds of surgery. Right.
And that has a whole new layer of complexity, doesn't it, For
managing their care during thoseprocedures?
Absolutely. So our deep dive today is all
about navigating that complexity, the really crucial
things to consider when managingpatients with these devices
during surgery. Yeah.
(00:42):
And we've got some great sourceshere, a really interesting large
scale study from Vienna, some practical guides to.
It's a good mix. It is and it helps us understand
the and you know how to handle the potential challenges.
It's pretty amazing how far thisfield has come.
I mean, our sources remind us this whole thing really kicked
off back in 1958. Wow. 50.
Yeah, the very first fully implantable pacemaker insertion
(01:05):
done under general anaesthesia, interestingly enough.
That's incredible. From just one patient then to
millions now. Quite a leap.
It really is. All right, so before we get into
the the operating room challenges, let's just make sure
everyone's on the same page. What exactly are these devices?
What are the main types we should know about?
Well, the sources mostly focus on two key types, pacemakers, or
(01:27):
PMS and implantable cardioverterdefibrillators, Icds.
Pacemakers fundamentally are there to help a heartbeat
speeding too slowly. They send out little electrical
impulses to keep the rhythm going at a safe rate.
Right, speeding things up if needed.
Exactly. Then you have IC D's.
Their main job is to detect and stop dangerously fast,
(01:49):
potentially lethal heart rhythmslike Vt or V fib.
How do they stop? Them usually by delivering an
electrical shock. But this is important.
ICD's can also pace the heart. They have pacemaker functions
built in for when the heart is too slow.
Ah OK, so PMS for slow rhythms, ICD's for fast rhythms.
But ICD's can also do the slow rhythm job.
(02:10):
Got it. And what are the actual physical
parts of one of these things? You can think of it as having
three main components. First, there's the pulse
generator. That's the device itself, the
brain if you like, containing the battery and all of the
complex circuitry. And these have shrunk
dramatically, right? Unbelievably, the sources note
they started around what, 120 grammes back in the early days?
(02:31):
Wow. And now they can be as small as
like 9 grammes. It's incredible miniaturisation.
Seriously. Like fitting a whole computer
system into something lighter than a than a standard battery?
Yeah, that's amazing engineering.
It really is then connected to the generator, you have the
leads. The wires.
Yep, insulated wires. They run from the generator,
which is usually implanted up inthe chest area, down into the
(02:53):
heart, typically threaded through a vein, and then right
at the tips of those leads are the electrodes.
These are the crucial contact points.
They deliver the electrical pulses to the heart muscle when
pacing is needed. And they listen to, right?
Exactly. They also sense or listen for
the heart's own intrinsic electrical activity.
That sensing part is key to how they operate.
(03:15):
OK, so they send signals and they listen for the heart's own
signals. Why does someone actually get
one implanted? What are the main reasons?
It usually boils down to problems with the heart's
electrical system. Oh, for pacemakers, it's often
things like symptomatic bradycardia, a heart rate so
slow it causes fainting or severe dizziness.
Right? Or certain types of heart block
where the signals just aren't getting through properly.
(03:37):
For Icds, it's typically for patients who are at high risk of
sudden cardiac death because of dangerous ventricular
arrhythmias. They've either survived 1
already or they have a heart condition that puts them at high
risk. And how does the device figure
out when to step in and pace, orwhen to just hang back and
listen? Is there like a setting?
There is, absolutely. It follows specific programmed
(04:00):
instructions, and these are often described using a special
code. It's called the NBG code.
NBG. Yeah, named after the groups
that standardised it. It's often presented as A5
letter code, but honestly in day-to-day practise you most
commonly see devices programmed using just the first 3 letters
and. What do those letters tell you?
Each letter signifies something specific.
(04:20):
The 1st letter tells you which heart chamber is paste.
The second tells you which chamber is sensed, and the third
tells you how the device responds when it senses the
hearts own beat. OK, so let's take an example.
What about VVII? Hear that one mentioned a lot.
VVI is super common, so the first V means it paces the
ventricle, the second V means itsenses the ventricle, and the
(04:42):
3rd letter I stands for inhibited.
That means its response when it senses a natural heartbeat in
the ventricle is to inhibit its own pacing pulse.
So it holds back if the heart isdoing its own thing.
Precisely. It listens, and if it doesn't
hear a natural beat within a certain time frame that it
paces, otherwise it stays quiet.That makes sense.
(05:02):
Blates its turn. And you mentioned VOO earlier as
maybe a default or temporary mode.
How's that different? Right VOO is quite different.
First V is paste in the ventricle, but the second letter
is O, meaning it senses in neither chamber or sensing is
off. No sensing none.
And the third O means its response to sensing is also O or
(05:24):
none. So basically it just paces the
ventricle at a set fixed rate. It completely ignores whatever
the hearts own electrical activity might be doing.
Less sophisticated. It is in a way.
It's called an asynchronous mode.
But that lack of sensing that just pacing regardless, can
actually be really important, even necessary in certain
(05:45):
situations like during surgery with potential interference.
OK. So that leads us right into the
operating room. You've got this patient, they
have the sophisticated little device, and you bring them into
an environment full of, you know, monitors, electrical
equipment and especially surgical tools that use
electricity. What's the number one headache
for these devices in the OR? The absolute biggest concern,
(06:06):
the one we really need to focus on, is electromagnetic
interference. EMI.
Yeah, basically external electrical or magnetic fields
that can seriously mess with howthe device is supposed to work.
And what's the most common source of EMI in the OR is it
the the electric cautery? Spot on Electrosurgery, what
most people call the Bovie and the sources are clear.
(06:27):
Monopolar electric cautery is much more likely to cause
problems than bipolar. Why is that?
It's all about the path the electrical current takes.
With bipolar, the current just flows between the two tips of
the instrument. It's very localised, very
contained. Right, like tiny tweezers.
Exactly. But with monopolar, the current
goes from the active tip throughthe patient's body all the way
(06:48):
to a grounding pad stuck somewhere else on their skin.
So a much bigger circuit throughthe patient.
A much bigger, less predictable circuit, and that creates a much
larger electromagnetic field that the pacemaker or ICD is
more likely to pick up his noise.
OK, so here's the really crucialpart.
What can actually happen if thatEMI does interfere with the
(07:09):
device? What are the dangers the sources
talk about? The effects can be pretty scary
honestly. One of the most critical is
inhibition of pacing. Inhibition, meaning it stops
pacing. Yes, the device senses the EMI
noise, mistakes it for a naturalheartbeat.
We call that over sensing and soit holds back its pacing pulse
just like it's programmed to do in VVI mode for example.
(07:31):
So if the patient needs that pacing.
Exactly. If the patient is pacing
dependent, meaning their own heart rhythm isn't adequate,
this in addition can cause theirheart rate to drop dangerously
low, severe bradycardia or even a systol.
No heartbeat at all. Wow, so the interference
literally trips the device into stopping, potentially stopping
the patient's heart. That's incredible.
(07:52):
Notably serious. What else?
Well, on the flip side, EMI can sometimes cause inappropriate
pacing or shocks. How so?
Some devices have these sensors,called rate responsive sensors,
that are meant to increase the pacing rate when the patient is
active, like sensing vibration or changes in breathing EMI can
sometimes falsely trigger these sensors, leading to leading to
the pacemaker suddenly pacing way too fast, causing
(08:15):
tachycardia when the patient doesn't need it.
And for ICDS it's even worse. The device might misinterpret
the EMI noise as a life threatening arrhythmia like V
fib and then it delivers a powerful, completely unnecessary
and very painful shock to the patient.
Yikes, getting shocked inappropriately during surgery.
I can't even imagine. Definitely something we have to
(08:37):
prevent, and it's not just aboutconfusing the device's software.
Strong EMI can potentially causeactual physical.
Damage. Damage to the device itself.
Or the leads, or even the heart tissue.
The electrical energy can generate heat.
This could potentially burn the heart tissue right where the
electrode touches it, or damage the insulation on the leads, or
even harm the circuitry inside the generator itself.
(08:59):
It could lead to temporary or even permanent malfunction.
So it can stop pacing, pace too fast, shock when it shouldn't,
or just break. That's quite a list.
It is, and there's one more thing.
Mode resetting really strong EMIcan sometimes overwhelm the
device's logic and cause it to to revert to a sort of factory
default or backup mode. Like a safe mode?
(09:19):
Kind of. Often it resets to something
basic like VDI or VOO. Now these modes are usually safe
in the short term, but they might not be the best mode for
that particular patient. And if you weren't expecting it,
you might even think the batterydied or something.
OK, so mainly the boovie. Are there other things in the OR
or hospital environment mentioned in the sources that
can cause interference? Yeah, less commonly problematic
(09:40):
in routine surgery, but still worth knowing.
Things like the guide wires usedfor putting in central lines.
If they haven't to touch or get very close to the device leads
in the heart, that mechanical contact can sometimes be
misinterpreted as heart signals.Causing inhibition or shocks
again. Potentially, yeah, especially
inappropriate ICD shocks or pacing inhibition.
(10:02):
MRI is obviously a huge source of EMI, which is why we have MRI
conditional versus MRI unsafe devices, a whole separate topic
really, right? And even some RFID tags, the
radio frequency ID things used for tracking equipment or
supplies, could theoretically interfere if they're held right
up against the device. And didn't I see something about
muscles like muscle contractions?
(10:23):
That's a more subtle one, but yes, strong skeletal muscle
twitches are contractions. Sometimes you see this with
certain muscle relaxants like sexy little choline used in
anaesthesia can generate tiny electrical signals called
myopotentials. And the pacemaker might pick
those up. A very sensitive pacemaker might
mistake those muscle signals forheartbeats and briefly inhibit
(10:45):
pacing. It's usually just a fleeting
effect, but it's possible. OK, so it's clear that bringing
a patient with one of these devices into surgery isn't
straightforward. It needs a really careful
thought out plan. How do the teams actually manage
this safely it? Absolutely has to be a planned
team effort. A multidisciplinary approach is
(11:05):
key. You need the cardiologist or the
electrophysiologist who knows the device, the device
technician, the surgeon and the anaesthesia team all talking to
each other. Communication is.
Vital. Totally.
Everyone needs to be on the samepage.
All right, let's break down the process.
What happens before the procedure, the prep phase?
What information is critical to gather?
First, the absolute basics. Confirm the patient has a
(11:27):
device. Sounds obvious, but you need to
ask. Look for the scar, feel for the
generator under the skin. OK, then you need the details.
What kind of device is it? Pacemaker or ICD?
Who made it? Different manufacturers have
different features, different magnet responses.
And critically, why was it implanted?
What's the underlying heart condition?
(11:47):
I guess the most important question is are they dependent
on it? Exactly.
That's probably the single most crucial piece of information.
Is the patient pacing dependent?Do they rely on that device for
a safe heart rhythm, or do they have a decent underlying rhythm
of their own? How do you figure that out?
Several ways. You look at their history.
Did they get the pacemaker because they were fainting from
(12:08):
a slow heart rate? Did they have a procedure called
an AV node ablation which essentially makes them
dependent? Or ideally you look at the data
from their last device. Check.
The interrogation report, yes. That report can often tell you
if the device is pacing 100% of the time, suggesting dependence,
or if the patient has their own rhythm kicking in frequently.
And how do you get that report or other device info?
(12:32):
The patient usually carries an ID card with basic info.
Getting the actual interrogationreport is best called the
cardiologist's office or the device clinic.
Sometimes the chest X-ray can help identify the device type.
ICD leads look thicker because they have Defibrillation coils
and check lead position. Is it standard practise to get
the device interrogated right before surgery?
(12:54):
It's highly recommended, especially if you anticipate
using monopolar cautery or if the surgery is near the device.
Getting it checked within say the last three, six months or
even the morning of surgery gives you vital up to date info
on battery life, lead function and the current settings.
And based on that check and the plan surgery, you might actually
change the settings temporarily.Yes, that's often necessary.
(13:17):
Temporary reprogramming is a keypart of the plan.
What kind of changes? OK, so if your patient is pacing
dependent and the surgeon is going to be using monopolar
cautery, especially anywhere above the belly button where the
current path is likely to cross near the device.
Right. Higher risk of interference?
Then you absolutely need to reprogram the pacemaker to an
asynchronous mode like VOO or Doo if it's a dual chamber
(13:41):
device. The mode that just paces
regardless of sensing. Exactly, that ensures the pacing
continues uninterrupted even if there's a tonne of EMI noise.
You're basically telling it ignore everything, just keep
pacing at this rate. Makes sense.
What else might you change? You generally want to turn off
any rate responsive features. Remember those sensors that
adjust pacing rate based on activity?
Yeah, well, things like surgicalretractors vibrating or even the
(14:05):
patient being mechanically ventilated can falsely trigger
those sensors and cause unwantedrapid pacing.
So turn that off. And crucially for ICDS, if
there's the significant risk of EMI, you must temporarily
suspend the anti tachyrhythmia functions.
Meaning turn off the shocking capability.
Yes, turn off the detection and treatment of tachycardia and
(14:26):
fibrillation. You absolutely do not want the
movie noise to trick the ICD into delivering an inappropriate
shock during surgery. That sounds critical, and you
have to do that in a safe place,right?
Absolutely. You only disable shocks in a
monitored setting where you haveexternal Defibrillation
immediately available, just in case the patient actually does
have a dangerous arrhythmia while the ICD function is off.
(14:47):
What about magnets? You hear about slapping a magnet
on the device? Is that a shortcut?
The magnet, Yeah, it's useful. Useful sometimes, but it's
definitely not a universal fix or a substitute for proper
reprogramming if EMI is expected.
How does it work? It depends on the device type
and manufacturer. For most pacemakers, applying
the correct magnet will switch it to an asynchronous pacing
(15:09):
mode like VOO or DO, but often at a specific magnet rate, which
might not be ideal. OK, so it's forces pacing for
PMS, what about ICDS? For most ICDS, putting a magnet
on suspends the shock therapy. It stops it from delivering
shocks. But does it change the pacing?
Generally no. This is the key point people
misunderstand. The magnet usually doesn't
change the pacing mode of an ICD.
(15:31):
So even with the magnet on, the ICD is pacing function can still
be inhibited by EMI if it's in amode like VVI.
So magnet on an ICD shocks off, but pacing might still stop due
to interference. Exactly.
So it's useful for quickly disabling shocks in an
emergency, maybe, but if you need reliable asynchronous
pacing during EMI, reprogrammingis the way to go.
(15:54):
Magnet response isn't totally standardised either.
Good to know. Not a magic wand.
OK, so planning done, reprogramming done.
Now we're during the procedure. Vigilance is key, you said.
What does that look like? Continuous monitoring is
baseline ECG constantly watched pulse oximetry, looking at the
waveform 2 For a peripheral perfusion blood pressure
(16:15):
monitoring, you need eyes on therhythm strip nonstop.
And backups ready. Absolutely.
External defibrillator pads should ideally be placed on the
patient prophylactically if you've turned off their ICD
function or if they're high risk.
At the very least, the machine and pads must be in the room,
plugged in, ready to go instantly.
Transcutaneous pacing capabilities should also be
immediately available. And what about the surgical
(16:36):
side? How can the team using the
cautery minimise the risk? There are definite techniques.
First, try to position the grounding pads so the current
path from the active movie tip to the pad doesn't run through
or near the pulse generator and leads.
Keep the current away from the device, right?
Also, avoid just waving the active electrode around near the
generator pocket, right? Use the lowest possible energy
(16:58):
setting on the cautery unit. That still does the job
effectively. And crucially, use it in short
intermittent bursts, not long continuous activations.
Like quick taps rather than leaning on the pedal.
Exactly. Give the device moments to
recover and function normally between bursts.
And of course, if bipolar cautery or an ultrasonic scalpel
can achieve the surgical goal, use those instead.
(17:21):
They generate much less EMI. Much safer alternatives if
practical. Definitely preferred when
possible. And what if, despite all the
best planning and precautions, you do see something weird
happening on the monitor? Like the heart rate suddenly
drops or the pacing spikes disappear.
If you suspect device interference or malfunction, the
rule is clear. Stop the source of interference
(17:42):
immediately. Usually that means stop the
electrocautery. Pause surgery.
Pause whatever's causing the suspected EMI.
Assess the patient, assess the rhythm, figure out what's going
on. You don't proceed until the
issue is understood and managed.Maybe you need to reposition the
grounding pad, switch to bipolar, or confirm device
settings. Haven't reset safety first.
(18:02):
Absolutely. OK, let's talk about outcomes.
That big Vienna study you mentioned looked specifically at
procedures where CIS were being implanted.
A bit different from managing them during other surgeries, but
it still gives us a window into the risks these patients carry,
right? It's as it looked at over 15,000
patients getting PMS or Icds. They track things like needing
(18:22):
CPR during the implant procedureitself and also mortality within
30 days and. What did they find?
Were complications common? The rates were relatively low.
Thankfully, meeting CPR during the actual implant happened in
only .39% of cases. Less than half a percent.
Right. And the 30 day mortality rate
was .8%. Now the authors made a point
about that .8%. They argued that while it might
(18:44):
sound a bit high for what's often an elective procedure,
their analysis suggested it wasn't really due to the implant
procedure itself, but more reflected the severe underlying
health problems of the patients getting the devices.
They compared it favourably to mortality rates seen after other
major surgeries in similarly frail populations.
OK. So the patients are often quite
(19:05):
sick to begin with. Did the study identify specific
things that put patients at higher risk for those bad
outcomes? Yes, a few key things stood out.
A major 1 was acute heart failure or AHF.
Having AHF at the time of the implant was a significant
independent predictor for both needing CPR during the procedure
and dying within 30 days. That really underscores the
(19:27):
fragility of those patients. It does.
Another interesting finding was about the anaesthetic technique
used for the implant. Oh, how did that matter?
Compared to just having local anaesthesia with standby
monitoring, using either sedation or full general
anaesthesia was linked to a significantly higher chance of
needing CPR during the implant. Wow, any idea why that they say?
The study showed the association, but didn't deeply
(19:50):
explore the why. It could be that patients
needing GA or deeper sedation were inherently sicker, or
perhaps respiratory effects of sedation played a role.
It's an interesting correlation from that specific implant
setting. What else?
Increased risk. For 30 day mortality, older age,
especially over 86, having a history of fainting before the
implant or having had CPR previously were all risk
(20:13):
factors. And unsurprisingly, other heart
problems like coronary artery disease or cardiomyopathy,
meeting blood pressure support with vasopressors or having low
oxygen levels also increase the risk of dying within 30 days.
Makes sense. Those are markers of sicker
patients. Was there any good news in the
data? Any trends?
Yes, actually a very positive finding was that the risk of
(20:35):
needing CPR during the implant procedure significantly
decreased over the long study period, which ran from 1997 to
2019. Well, that's.
Great. Yeah.
It suggests a real learning curve or improvements in the
technology, the techniques, maybe team experience.
Over those couple of decades, practise got safer.
That's very encouraging to hear.OK, So the procedures done, the
patient's heading to recovery, What's critical in the after the
(20:58):
procedure phase to make sure everything's OK and they go home
safely? OST U management is just as
vital. You can't relax yet.
Continuous cardiac monitoring watching their heart rate and
rhythm needs to continue in the recovery area or ICU.
And Kee the Backus nearby. Absolutely.
That external pacing and Defibrillation equipment should
remain immediately available until you're sure the patient is
(21:20):
stable and, crucially, until thedevice has been checked in any
temporary settings have been putback to normal.
So checking the device again afterwards is important.
Post operative device interrogation is key.
The source is strongly recommended, especially in
certain situations. Like when?
Definitely if any settings were changed before or during the
surgery. If it was an emergency operation
(21:42):
where you didn't get a full pre op assessment.
If there's any suspicion that the device might have been
affected, like if there was a lot of EMI used nearby, or if
the patient had large fluid shifts, or if the ICD shocks
were turned off. What does that post op check
tell you? It confirms the device is still
working properly, cheques the battery status again, make sure
the leads are sensing and pacingcorrectly, and it's your chance
(22:03):
to restore the patient's optimalpermanent settings.
And when should those permanent settings be put back?
Can they go home with the temporary?
Ones no. The standard permanent settings
should ideally be restored before the patient leaves a
monitored setting like pay CU orthe hospital ward.
If for some reason an interrogation can't happen right
away, postdoc. The recommendation is to get it
(22:23):
done within 30 days. Got it.
This has been a really comprehensive look.
It's definitely clear that managing these patients requires
a lot more than just, you know, standard surgical care.
It really highlights how sophisticated medical technology
requires equally sophisticated planning, teamwork and vigilance
from the human side. So if you had to boil it down,
(22:44):
what's the absolute key takeawayfor our listeners about managing
patients with CI ES around the time of surgery?
I think it comes down to a few core principles.
First, understand the specific device your patient has and and
why they have it. Second, anticipate the potential
interactions, especially EMI from electric artery.
Third, meticulous planning and risk assessment beforehand. 4th,
(23:08):
seamless communication among everyone involved.
Anaesthesia, surgery, cardiology, device techs, and
finally continuous careful monitoring throughout the entire
perioperative journey. And being ready to act if
something goes wrong. Exactly.
The technology is amazing, but safe care still relies on those
fundamental clinical skills, assessment, preparation and
(23:29):
readiness to intervene. It's been fascinating, so here's
a final thought for you, the listener to Mull over as this
CIE technology keeps getting smarter and smaller.
We're talking wireless monitoring, maybe even sensors
built into the leads that track hemodynamics in real time.
How might that change the game? Will the need for direct human
cheques and interventions like reprogramming or post op cheques
lessen? Or will it just shift how
(23:50):
healthcare teams need to coordinate and use that data in
the future? Something to really think about.
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