Time Stamps

  • 02:51 What are the different types of pacemakers and defibrillators? Who is it indicated for? How can where the leads clue you what the implantable device may do?
  • 21:28 How to determine which type of device your patient has?
  • 25:10 What can a device interrogation tell you and doesn’t tell you?
  • 32:13 Do all patients with bacteremia needs their implantable cardiac devices taken out? 
  • 38:44 End-of-life considerations with pacemakers vs. ICDs 


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Show Notes

What are pacemakers?

  • Devices implanted in the body to treat bradyarrhythmia, AV conduction disease, or severe systolic heart failure.
  • Common class I indications (see guidelines for additional indications)
    • Sinus node dysfunction
      • Symptomatic bradycardia
      • Symptomatic chronotropic incompetence
      • Tachy-brady syndrome
    • AV conduction disease
      • Any 3rd degree AV block (with or without symptoms)
      • Any Mobitz type II AV block with QRS > 120 ms (with or without symptoms)
      • Symptomatic 2nd degree AV block (Mobitz type I or II)
    • Severe systolic heart failure
      • LVEF < 35%, left bundle branch block, and NYHA class II or greater symptoms, despite optimal guideline-directed medical therapy for 90 days
  • Types of traditional pacemaker systems:
    • Single lead (rare): 
      • Usually in the right ventricle (RV)
    • Dual chamber: 
      • RA and right ventricle (RV)
    • Cardiac resynchronization therapy (CRT), also known as biventricular pacing: 
      • RA, RV, and coronary sinus
  • Function of pacemaker depends on number and location of leads:
    • For example, a dual chamber (i.e., RA and RV) pacemaker can sense electrical activity in the RA and RV. 
      • When it notices AV block, or a lack of signal conduction between the chambers, it can deliver an electrical stimulus to the RV to bypass the blocked pathway. 
      • It also kicks in when it senses the heart rate is lower than what it is programmed to sense (sinus node dysfunction).
    • Since cardiac resynchronization therapy (CRT) or biventricular pacing have leads RA, RV, and coronary sinus, CRT can help both ventricles contract at the same time. This is indicated in patients with low ejection fraction <35% and LBBB.

What are ICDs?

  • ICDs are devices implanted in the body to treat life-threatening tachyarrhythmias, including ventricular tachycardia (VT) and ventricular fibrillation (VF). 
    • Traditional ICDs also have all the functionality of pacemakers. 
  • What are common class I indications? (see guidelines for additional indications)
    • Primary prevention
      • Ischemic cardiomyopathy – EF 30% and prior myocardial infarction
      • Any cardiomyopathy – EF 35% despite optimal guideline-directed medical therapy for 90 days
      • Other conditions placing patients at high risk for life-threatening tachyarrhythmias, such as symptomatic congenital long QT syndrome
    • Secondary prevention
      • Prior VF or unstable VT without recent myocardial infarction
      • Prior sustained VT with significant cardiomyopathy 
  • How do ICDs treat tachyarrhythmias?
    • Anti-tachycardia pacing 
      • ICD detects life-threatening tachyarrhythmia and delivers small electric currents with the goal of interrupting a dysfunctional electrical pathway. 
      • Can avoid giving a shock!
    • Defibrillating shock

How to determine which type of device your patient has?

  • Ask the patient
    • Patient may know or have a device identification card. 
  • Review the patient’s medical record for documentation of a device. 
  • Check the chest xray.
    • Identify the number and location of the leads. 
    • How do you distinguish ICD from pacemaker?
      • Look for thickening at the end of a lead, which indicates it is an ICD.
    • See examples in ReadingRoom Teaching “byte”
    • “There’s an app for that!”
      •  Consider using a smartphone application, such as Pacemaker ID or Cardiac Rhythm Management Device-Finder, to identify the device manufacturer. 
  • Specifying the device type and manufacturer is helpful when placing a cardiology consult, as the equipment used to interrogate pacing devices varies by manufacturer.

What is a device interrogation

  • Determines whether or not the device is functioning properly
    • Lead function
    • Battery life
    • Programming (e.g., mode)
  • Event log
    • Can help clinicians correlate the patient’s symptoms to cardiac events
    • Of note, only records what it is programmed to record – may not include clinically significant events depending on programming

How to manage patients with a pacemaker or ICD who develop a bloodstream infection

  • Devices may need to be removed
    • However, device removal is often high risk and requires careful consideration. 
  • Involve infectious disease and electrophysiology (or cardiology) teams EARLY for any patient with a bloodstream infection and cardiac pacing device. 
  • Device is typically removed for persistent infections or transient infections WITH highly virulent organisms (e.g., Staphylococcus aureus or fungi), as the device is considered seeded in these scenarios. 

How to approach end-of-life considerations in patients with pacemakers or ICDs? 

  • Pacemakers do not need to be turned off. 
  • ICDs may be appropriate to turn off if a patient is actively dying and declines resuscitation, as the shocks can be uncomfortable to the patient and difficult for the family to see.


Dr. Shreya Trivedi: Welcome to the Core IM 5 Pearls Podcast, bringing you high-yield evidenced-based pearls. I’m Dr. Shreya P. Trivedi, an internist at BIDMC.

Dr. Aaron Dunn: I’m Dr. Aaron Dunn, a resident at BIDMC. On today’s 5 Pearls episode, we’re talking about all things pacemakers and ICD.

Dr. Shreya Trivedi: Let’s get started with the pearls we’ll be covering in this episode. Test yourself by pausing after each of the 5 questions. Remember the more you test yourself, the deeper your learning gains.

Dr. Aaron Dunn: Pearl 1: Pacemaker and ICD function and indication.

Dr. Shreya Trivedi: What are the different types of implantable pacemakers and defibrillators, what are is their functions and who is it indicated for? 

Dr. Aaron Dunn: Pearl 2: Recognizing device type.

Dr. Shreya Trivedi: How do you tell what type of implantable cardiac device your patient has? 

Dr. Aaron Dunn: Pearl 3: Device Interrogation.

Dr. Shreya Trivedi: When should you consult electrophysiology on a patient with an implantable cardiac device? And what exactly is a device interrogation? 

Dr. Aaron Dunn: Pearl 4: Bacteremia.

Dr. Shreya Trivedi: How do you approach a patient with bloodstream infection in a patient who has an implantable pacing device? 

Dr. Aaron Dunn: Pearl 5: End of life care.

Dr. Shreya Trivedi: How do you approach end-of-life with a patient who has a pacemaker and how do those conversations differ?

Pearl 1

What are implantable pacemakers and defibrillators? And why do people get these devices? 

Dr. Shreya Trivedi: Let’s start off with pacemakers before we get defibrillators or ICD – who needs a pacemaker and what does a pacemaker actually do?

Dr. Aaron Dunn: We sat down with Dr. Joshua Cooper, an electrophysiologist from Temple University who does a great job of simplifying things. He helped us develop a framework to think about pacemakers in 3 big buckets. 

Dr. Joshua Cooper:  A pacemaker is an electronic device that’s implanted in the body, and its goal primarily is to prevent the heart from falling below a certain rate from going too slow. The secondary feature of pacemakers is to coordinate chambers, in particular, the top and bottom half of the heart to make sure the atria and the ventricles are working in timing, in sync with each other. And then the third thing that a pacemaker can do is to coordinate the walls of the ventricles to squeeze in a simultaneous way.

Dr. Shreya Trivedi: Right. Just like there are 3 main things it does, there are 3 types of pacemaker systems. And what’s been really helpful is understanding that the # pacing leads and where their location is can give us a clue about which type it is and what pacemaker can do.

Dr. Andy Locke: The first type is a single chamber device. That means that there’s a single wire that goes into the right ventricle, and the only job of the pacemaker in that case is to ask the question, is the ventricle beating below a certain rate? If it is, it will pace.

Dr. Aaron Dunn:  That is Dr. Andy Locke, an electrophysiologist at BIDMC and instructor at Harvard Medical School.

Dr. Andy Locke: When the heart rate and the ventricle goes below a certain point, the second type of pacemaker system is a dual-chamber pacemaker. That pacemaker has a wire that goes into the right atrium and then a second wire that goes into the right ventricle.  This system, same thing, it looks at the heart rate and it says if the heart rate drops below a certain point, it will kick on and start pacing the heart. But the bonus of this system, because there’s a wire in the atria and the ventricle, is that the pacemaker can time that atrial contraction with the ventricular contraction, so that’s can create AV synchrony.

Dr. Aaron Dunn:  The last type of pacemaker, called cardiac resynchronization therapy, also known biventricular pacing, is a fancy way of saying, “we are stimulating both ventricles to contract at the same time,” and to do that there are 3 leads: one in the right atrium, one in the right ventricle, and one in the coronary sinus.

Dr. Shreya Trivedi:  I don’t know about you, Aaron, but its annoying because there is a dual chamber which 2 leads and then there is cardiac resynchronization therapy CRT which is also called biventricular pacing, but that’s ACTUALLY 3 leads.

Dr. Aaron Dunn: Even though that bi- prefix suggests otherwise!

Dr. Shreya Trivedi: I’m glad we are calling it out so we can keep it straight – dual chamber pacemaker is two leads and biventricular pacing refers to cardiac resynchronization therapy which is actually 3 leads, annoyingly.

Why do patients need pacemakers?

Dr. Shreya Trivedi:  Ok, so now that we covered the types, the natural next question is which patients will pacemakers be the most helpful in?

Dr. Andy Locke: there are really two main indications for pacing. One indication is sinus node dysfunction. The other indication is atrial ventricular or AV conduction disease. The sinus node again is a structure in the right atrium that sets the heart rate. And over time there’s gonna be a variety of reasons why someone develops sinus node dysfunction. The most common cause is just through aging and fibrosis. The sinus node stops working well. And  what that can look like is patients can come in with sinus bradycardia, they can come in with a junctional rhythm They can have intermittent sinus node dysfunction. So one day they’re fine, they can have a pause they can feel what’s called chronotropic incompetence. They can feel like they can’t get their heart rate as high as they want their heart rate to be when they exercise or they walk so they feel short of breath. 

Dr. Kamala Tamirsia: This is your 60 odd year old young relatively young patient who basically says, Hey, I had a syncope, but then over the last three months I’ve noticed that as I exercise, I get more and more tired. I’m unable to increment my heart rate. 

Dr. Shreya Trivedi: That is Dr. Kamala Tamirisa, an electrophysiologist at the Texas Cardiac Arrhythmia Institute. And  in addition to that chronotropic incompetence or sinus pauses, the other thing that falls into the sinus node dysfunction umbrella, is tachy-brady syndrome.

Dr. Andy Locke: If you have a patient that has tachy-brady syndrome, by definition they have sinus node dysfunction because that’s the bradycardic part of it.

Dr. Kamala Tamirsia: So this is your patient with AFib where they go at a  rate of 120s, 190s, and when they convert from AFib or in sinus, the heart rate drops to fifties and forties. And what do you do? You need to rate control, but then you have bradycardia on one end.

Dr. Shreya Trivedi: Yeah what do you do, put a pacemaker in that! And you know, I’m glad we are covering the indications because I recently had a patient whose notes kept saying “afib s/p pacemaker” and made me go wait a minute that’s not why pacemakers indicated.

Dr. Aaron Dunn: Was it actually tachy-brady syndrome?

Dr. Shreya Trivedi: Yep, confirmed after digging into cardiology notes from years ago and changed it in our notes

Dr. Aaron Dunn: So takeaway is, yeah, patients with afib MAY get a pacemaker, but it’s REALLY because of sinus node dysfunction.

Dr. Shreya Trivedi: Okay with that clarified, let’s move on to talking about 2nd big indication of pacemakers, “AV,” dysfunction 

Dr. Aaron Dunn: When I think of AV dysfunction, I think of all the things we get tested on for boards: the Mobitz type I, type II, squiggles in my head.

Dr. Kamala Tamirsia: The keywords, every time I tell people the keywords are symptomatic. But that changes the symptoms pretty much are not too relevant if you have a complete hard block without a reversible cause or high grade AV block with Mobitz type two.

Dr. Aaron Dunn: So with symptomatic or high-degree AV dysfunction, we will reach for the pacemaker that has dual chamber pacing to both atrium AND the ventricle, which helps the signal bypass the diseased tissue and get to the ventricle. 

Dr. Shreya Trivedi: That makes a lot of sense. So that’s dual chamber pacing, and while we are thinking about indications for different types of pacemakers, when does a patient get 3 leads like cardiac resynchronization or biventricular pacing? When do we reach for that?

Dr. Andy Locke: So there are certain times when someone’s heart function is low and some of that decreased heart function is due to electrical dyssynchrony – dyssynchrony between when the right ventricle beats and when the left ventricle beats. The way that we know that someone is dyssynchronous is really looking at the surface ECG If they have a very wide QRS, and typically it’s, it’s a left bundle branch block that causes electrical, mechanical dyssynchrony, that’s when, um, we think about cardiac resynchronization therapy.

Dr. Shreya Trivedi: Ok so CRT or biventricular pacing is going to help people a low ejection fraction <35% and LBBB, meaning they probably need help with synchronizing their left and right ventricle with the hope it will help the patient’s heart failure/cardiac output.

Dr. Aaron Dunn: This may be a good place to do a mid-pearl recap, pacemakers are implantable devices with 3 big indications (1) sinus node dysfunction, which includes things like symptomatic bradycardia, chronotropic incompetence and tachy-brady syndrome and then (2) AV node dysfunction especially if they are symptomatic or have high degree AV block, and the last indication (3) is heart failure that’s due to ventricular dyssynchrony, which will show up as a left bundle branch block on ECG. 

Dr. Shreya Trivedi: And thinking about the type of pacemaker based on where those leads are, a single chamber pacemaker, that 1 lead is usually in the RV can help with pacing only if the ventricle is going too slow, a dual chamber pacemaker and help with that too, AND because there is another lead in the atrium also can help with sick sinus syndrome or if there is AV dysfunction. Last CRT or biventricular pacing has 3 leads with the extra lead in the coronary sinus on left ventricle so has the additional functional helping both ventricles contract at the same time.

What is an ICD?

Dr. Aaron Dunn: Ok, let’s start off by clarifying something that most people don’t realize: traditional ICDs have ALL the capabilities of a pacemaker AND another important function.

Dr. Joshua Cooper: A defibrillator, the primary function is to terminate a life-threatening fast arrhythmia, ventricular fibrillation, or ventricular tachycardia. 

Dr. Shreya Trivedi: Yep, those life-threatening fast arrhythmias that we all make us sweat a little.

Dr. Aaron Dunn: To understand how an ICD treats those fast rhythms, we have to understand WHY the fast rhythm is happening in the first place. 

Dr. Andy Locke: So the majority of VT or that these devices treat are reentrant arrhythmias, which means somewhere in the heart there’s a little scar and there’s the scar is made up of surviving myocardial bundles and infarcted myocardial bundles. And because of that heterogeneity you get, the electrical current gets stuck there. And in the perfect situation it can cause a loop and it can reenter on itself. And when it does that, that’s when you have reentrant VT. 

Dr. Shreya Trivedi: What I didn’t know before this episode is that ICDs stop these scary rhythms with more than just a shock.

Dr. Aaron Dunn: Right, so as many people know, ICDs can deliver a shock, which resets the heart’s electrical system, but shocks can be really painful. So, most ICDs are programmed to try something else first, called anti-tachycardia pacing or ATP.  

Dr. Andy Locke: The only way to potentially terminate that without a shock is to pace faster than that tachycardia. So it will pace and eventually as the ATP delivers pulses, it will collide with that circuit and it gets closer and closer and closer. And eventually the ATP will enter that circuit and cause collision in the circuit and then terminate the circuit. 

Dr. Shreya Trivedi: Whoa, I feel like anti-tachycardia pacing is that competitive gunner that’s like no, I’m gonna be faster and take over the conduction and YOU WON’T even feel it or know about it! 

Dr. Aaron Dunn: Yep, ICDs will first try to block the fast rhythm with anti-tachycardia pacing and in that case the patient feels nothing, but if ATP pacing doesn’t work, it will deliver a shock.

Dr. Joshua Cooper: It’s a big sudden jolt in the chest. People describe it as being kicked by a horse or being hit by a brick or a bat. But it’s important to point out that it’s over almost before you realize it’s almost more the shock, the surprise of the shock than any lingering discomfort. And the reason that it is uncomfortable is because the electrical signal that restores a normal heartbeat also causes all the muscles of the torso to contract all at once so imagine all of your chest muscles and arm muscles suddenly squeezing quickly and then relaxing.

Dr. Shreya Trivedi: So I guess we can tell our patients that if an arrhythmia does come up, it can be painless with ATP pacing but also give them a heads up of what a shock may feel like that to maybe decrease the intensity of the surprise. I also appreciated hearing how Dr. Cooper also reassures his patients, especially if the ICD is for primary prevention.

Dr. Joshua Cooper: Patients who have a primary prevention defibrillator implanted generally have no arrhythmias and no shocks. A lot of the primary prevention studies that compared patients with a certain ejection fraction with or without a defibrillator in many of those studies, only one out of 10 patients or so in a five year follow up period ends up even having the type of rhythm that a defibrillator would treat. That means 90% of those patients with primary prevention devices will just have it sit there as an insurance policy that they will never need, at least in that timeframe. And so I reassure them that this is just there as a little guardian angel, a little ambulance walking around with them ready to kick in if it’s needed, but chances are they just won’t need it for that reason if again, it’s put in a preventative fashion.

Dr. Shreya Trivedi: I can’t wait to use that “little ambulance walking around with them” analogy next time I talk to someone with ICD since most patients with primary prevention ICDs will not experience shocks. 

Dr. Aaron Dunn: I’m shocked. 

Dr. Shreya Trivedi: Ohh, Aaron…

Dr. Aaron Dunn: Sorry, I couldn’t resist.

Why do patients need ICDs?

Dr. Shreya Trivedi: Now, that we know ICDs can do everything a pacemaker can AND on top of that, do anti-tachycardia pacing function or deliver shocks to stop life-threatening arrhythmias, who are ICDs indicated for? Let’s cement that.

Dr. Aaron Dunn: The most intuitive indication is secondary prevention, so this is patients who have ventricular tachycardia, ventricular fibrillation or cardiac arrest and we think it’s a cardiac cause. You want to prevent a second event. 

Dr. Shreya Trivedi: Secondary prevention makes sense, what about primary prevention?

Dr. Andy Locke: Primary prevention is patients that we know that are at risk for ventricular tachycardia, ventricular arrhythmias, but they haven’t had one yet. So if someone has heart failure and an EF less than 35%, you can put a defibrillator in someone. You wanna make sure that when you make that decision that the patient has had at least three months of goal directed medical therapy, and you wanna make sure that you’re at goal.

Dr. Shreya Trivedi: And as a throwback to our GDMT episode, at goals means they have 3 months of GDMT so good doses of B-blockers, mineralocorticoid receptor antagonist, angiotensin receptor/neprilysin inhibitor (or an ACE/ARB), and now we have SGLTs.

Dr. Andy Locke: There’s like so many new drugs. And what we’re finding is patients are really responding well to these drugs. So the event rates that the trials used to show they’re not, they’re potentially not as high as they used to be.

Dr. Shreya Trivedi: I appreciate hearing nuance, that we are in a different era with these really good GDMT, and maybe even more motivation for us to maximize the doses as much as a patient can tolerate, so our patients don’t need that ICD.

Newer Devices

Dr. Aaron Dunn: Ok now that we have covered all that ground on traditional ICDs and pacemakers, I actually was really excited to hear about newer types of implantable cardiac devices like leadless pacemakers. 

Dr. Andy Locke: Leadless pacing is also very cool. So imagine instead of having a, um, a battery and a wire, you have a small device that’s about the size of a bullet that goes directly into the right ventricle. 

Dr. Shreya Trivedi: Whaaat? 

Dr. Aaron Dunn: I know, right? Leadless pacing can be a good option for patients who AREN’T good candidates for traditional pacemakers. 

Dr. Andy Locke: You’re not expecting people to live, you know, a 95 year old with, with, um, with dementia who may have a hard time letting a pacemaker site heal. This is a great option for people. 

Dr. Aaron Dunn: Leadless pacing may be good for patients who are at high risk of infection OR patients with poor vascular access options (like those with occluded veins OR patients on dialysis). 

Dr. Shreya Trivedi: I’m glad we have that option for them. We also heard about subcutaneous ICDs – whats the all the buzz about subq ICDs. 

Dr. Kamala Tamirsia: The device goes along the left lateral chest, along the mid axillary line and the lead is basically tunneled under the skin and we use a tunneling device and tunnel it under the skin and place it next to the sternum. Everything in the subcutaneous space, the beauty of the device, as the name says subcutaneous defibrillator, we do not invade the vascular space. So the no leads travel in the venous system, which is excellent. Risk of infections goes down, complication rates go down too. 

Dr. Shreya Trivedi: This device definitely has lower rates of infection, but as Dr. Tamarisa warned us, there are limitations. Subcutaneous ICDs can’t pace or can’t do anti-tachycardia pacing; it can only shock, which can definitely be a downside for patients if they need a pacemaker function as well or if they are experiencing frequent episodes of ventricular tachycardia requiring shocks.

 Dr. Aaron Dunn: It’s so cool to hear about these newer technologies. I think what I’m taking away from this is that pacemakers and ICDs are evolving technologies and that there may be options for patients that we aren’t aware of.

Dr. Shreya Trivedi: So let’s cement this beast of a pearl of pacemaker and ICDs. The number of leads and anatomy of the pacemaker is gonna help us understand its main indication. Let’s do some retrieval practice: what should we think when we see a single lead, single chamber pacemaker?

Dr. Aaron Dunn: So a single chamber pacemaker, which we really don’t see that often is going to kick in when the heart rate falls too low. 

Dr. Shreya Trivedi: What about dual chamber?

Dr. Aaron Dunn: So it’s going to help bypass the AV node and it’s going to be helpful for patients who have high degree or symptomatic AV block. And on top of that, it can kick in just like a single chamber lead when the heart rate falls too low.

Dr. Shreya Trivedi: And lastly what about when you see s/p CRT or biventricular pacing?

Dr. Aaron Dunn: CRT has 3 leads. CRT is for patients with EF less than or equal to 35% who also have dyssynchrony between the ventricles (which we can see as a left bundle branch block on ECG). Now let me quiz YOU on ICDs. What should we think about when we see an ICDs in someone’s one liner?

Dr. Shreya Trivedi: So that person has it in either for secondary prevention (meaning they already had a VT or vfib event in the past) or for primary prevention so this patient likely has a low EF is low despite good GDMT for months and is at risk for those arrhythmias. ICDs can do everything a pacer can do, but can also deliver shocks or do anti-tachycardia pacing, which basically delivers a small currents to disrupt the arrhythmia. 

Pearl 2

How do I tell what type of device my patient has? 

Dr. Shreya Trivedi: Ok Aaron, so let’s say we are admitting a patient to the hospital, and we see in the medical record or on their chest that they have some implantable device– not sure which one. What I didn’t know before this episode is that knowing what brand that pacemaker or ICD is can actually help our electrophysiology colleagues a ton.

Dr. Aaron Dunn: Yeah, especially if we are asking them to do a device interrogation, if we can figure out what type of implantable device they have, it helps our cardiology colleagues know what equipment to bring to the bedside.

Dr. Andy Locke: Yeah, I don’t know if you’ve ever seen the fellows running around with the, just the worst consult to get is it’s a device, you don’t know what brand. So you’re bringing four of those with you and it’s inevitably two in the morning and you’re running around. 

Dr. Shreya Trivedi: Yep we can save them having to run around 4 device interrogation machines. So where do we start with figuring it out?

Dr. Andy Locke: The first thing I would say is to ask the patient, you would be amazed to know that patients know what they have and, and if they don’t know, their kids may know or their partner may know. I mean, just ask them. 

Dr. Aaron Dunn: But then again, we have all been burned before by a patient misremembering something

Dr. Joshua Cooper: Many people with a defibrillator will refer to it as a pacemaker, not really understanding the difference between them. So simply asking a patient, what kind of device do you have in, they may say the wrong thing.

Dr. Andy Locke: The second thing, they may have a card with them that says exactly all the, all the device manufacturers mail, they actually give temporary cards and then they mail patient cards once they have an implant. So almost if they forget, ask them to look into their wallet.

Dr. Aaron Dunn: Yes, but what if they don’t know, don’t have a card or the wallet is still at that good ol’ outside hospital emergency room? 

Dr. Andy Locke: If you don’t have that availability, a chest x-ray is your best friend. When you look at a chest x-ray, there are a couple clues as to what to know as so as, so as to how you can know what they have. Okay. Um, the first clue, So the first thing you can decide is, is this a single chamber, dual chamber, or BiV system. 

Dr. Shreya Trivedi: How do we tell if it’s a pacemaker or an ICD? Since ICDs can do everything pacemakers can, both can have 1, 2 or 3 leads.

Dr. Aaron Dunn: So here the size of the leads is important. If you look at an x-ray, an ICD has a thick coil at the end, whereas a pacemaker lead will be thin all the way through.

Dr. Shreya Trivedi: This didn’t stick for me until i saw the images in a recent reading room byte that we will link in the show notes we have to cement it.

Dr. Aaron Dunn: Oh yeah, definitely check out that reading room byte. Also, if you can’t tell who the manufacturer of a pacemaker is simply by looking at a chest xray, we learned about two cool free apps – Pacemaker-ID and Cardiac Management Device Finder where you can take a picture of the chest x-ray on your phone, and it will tell you the manufacturer, based on how it appears. 

Dr. Shreya Trivedi:  Let’s summarize this quick pearl on figuring out what type of pacemaker or ICD our patients have. It’s a good idea to start by asking the patient, particularly if they have a card with the brand name and type. Another way, you can find out is looking at the number of leads on the x-ray or if it has a thick coil at the end of the lead to indicate that it’s an ICD.

Pearl 3

When should you consult  electrophysiology on a patient with an implantable cardiac device? And what exactly is a device interrogation? 

Dr. Aaron Dunn: Ok, so let’s return to that patient we were admitting to our internal medicine service with a cardiac pacing device. Now, we have figured out how to identify what type of device they have.  But when should we consult electrophysiology? 

Dr. Joshua Cooper: We get called all the time for device interrogations because a patient is admitted with a device in place, and the sort of knee-jerk reaction is, well, the device is there, we should interrogate it, without really a specific question. 

Dr. Shreya Trivedi: You know I think one of the blind spots that we don’t realize is that every person who has an implantable device sort of is  being monitored for anything major, even without a formal interrogation.

Dr. Joshua Cooper: Recognize that patients with a defibrillator or a pacemaker are under close monitoring by their electrophysiologist, which nowadays includes remote device monitoring, that sends us regular reports.

Dr. Aaron Dunn: We asked Dr. Cooper to tell us how these consult conversations go… 

Dr. Joshua Cooper: Our first question is, well, what is the question? How can we be helpful rather than just go through an exercise with no purpose? And so if the patient had syncope, sure, did an arrhythmia occur, that’s very easy and it’s our pleasure. If they say, well, the patient’s just not been feeling well, well, that it’s unlikely that a device interrogation is going to give you additional information beyond what you’ll already have acquired in the form of an EKG. For example, let’s say someone has new atrial fibrillation, you don’t need a device interrogation to detect that. In fact, if their device doesn’t have an atrial lead, then it won’t know that atrial fibrillation is occurring at all. For example, a single chamber ICD with a lead in the right ventricle will not be aware that atrial fibrillation is occurring.

Dr. Shreya Trivedi: That’s a really nice reinforcement of pearl 1 on how the anatomy of device can tell us what it can and can’t do! I think the other thing that can help us ask better consult questions is understanding what that device interrogation actually tells us and not tell us.

What is a device interrogation?

Dr. Joshua Cooper: Interrogation of the pacemaker will have two purposes. One, to make sure the leads in the pacemaker are functioning normally.

Dr. Aaron Dunn: So what that means is the interrogation tells us about the device’s function: what it’s programmed to do, what parts of the heart the device is sensing and pacing, as well as a check in on the device’s battery life.

Dr. Joshua Cooper: And number two, to see if there’s anything in the tachycardia log to suggest that it coincided with the syncope event, they had a fast rhythm, but it would have to be extremely fast to cause syncope. Rapid atrial fibrillation, even in the one eighties, one nineties, 200 usually is not fast enough to cause fainting.

Dr. Andy Locke: So all of these devices have event logs where you can go back and see how often is a patient pacing, how often are they in AFib, how long are the AFib episodes? Are they having episodes of VT? Are they having PVCs? How many PVCs are they having? 

 Dr. Shreya Trivedi: So that event log, yes, can be a wealth of information, but we also have to understand the limitations of a device interrogation because it won’t tell you everything that happened with the patient. So that event log will only tell you the things that the device is programmed to record and do.

 Dr. Joshua Cooper: It’s important to recognize that there could have been an arrhythmia that fell outside the bounds of the programming of the defibrillator. What if the patient had VTach at 195 beats per minute? The defibrillator programmed at 200, for example, wouldn’t detect it and wouldn’t report it unless it was programmed with a reporting zone where that fast rate fell into a zone that the defibrillator was told to save that event in its memory and or treat it.

 Dr. Aaron Dunn: This means that an “unremarkable” or “normal” interrogation doesn’t necessarily mean that the electrical system of the heart is normal.

 Dr. Shreya Trivedi: So given that device interrogation definitely has some limitations, I wonder when our antenna should go up to alert us that a device interrogation for one of our patients might be missing something important. 

 Dr. Aaron Dunn: Great question, Shreya! Dr. Cooper gave us a great example when we sat down with him of just that. He was taking care of a patient with cardiac sarcoidosis and complete heart block and they came in with severe lightheadedness. They had an ICD placed and their symptoms resolved. 

Dr. Joshua Cooper: The patient did well for a number of years and then she reported that She said, I, I’ve had a couple of these spells that feel a lot like what, before you put my first pacemaker in, and the device interrogation was benign, the leads were fine, the thresholds were good, there were no arrhythmias in the device logs, but my antenna went up because I said that’s not right. If you feel like you’re having lightheaded spells and you say they are very reminiscent of your previous ones, there’s a problem. There can be an issue with the wires. As I said earlier, the wires, the leads from pacemakers and defibrillators are the weakest link of these systems. They over time can get damaged. The insulation can rub away. And those problems can be intermittent. You may do a full interrogation and see nothing wrong, and yet there is a problem that is an intermittent problem that you are not able to detect at that moment. You need to further investigate. A negative normal interrogation does not mean that there isn’t a problem. And in that particular patient, we actually gave her a heart monitor to take home. and sure enough she had further episodes and she had both loss of ventricular capture events and oversensing with inhibition of pacing. And we told her, we saw that, we said, come right to the emergency room. She came in and sure enough, one of her leads had an insulation break in it that intermittently was allowing current to escape out the side of the lead and not being fully delivered to the heart. And also when she was moving her arm, and she had periods of asystole. So take a patient’s complaints seriously and recognize that the story is not over with a device interrogation. If you have a story that is worrisome in particular lightheaded spells or fainting spells, that’s the biggest red flag you could have that there may be an issue.

Dr. Shreya Trivedi: Wow, what a great patient story. We all need these stories to keep ourselves humble. i think takeaway for me is asking myself what is the device programmed is programmed to sense and treat and more specifically what heart rates or arrhythmias is that device programmed to capture in the event log and is what’s on the event log correlates with any of the patient’s symptoms.

Dr. Aaron Dunn: The other thing we get from a device interrogation that we didn’t talk about is the pacemaker mode, which really feels like a bunch of random letters. One way to think about pacemaker modes is to use the mnemonic “PACERS,” which we heard about courtesy of Dr. Andy Locke. 

Dr. Shreya Trivedi: Yeah, we unfortunately had to cut it out for time, but we did put it in our show notes and infographic and great to have pull up on rounds and work through the mode settings as a team.

Pearl 4

How do you approach a patient with bacteremia who has an implantable pacing device? 

Device Infection and bacteremia 

Dr. Aaron Dunn: Ok, so let’s change gears to a scenario we unfortunately find ourselves in at least a few times a year. It’s the patient who has a pacemaker or ICD and you get a call from micro lab – positive blood cultures.

Dr. Kamala Tamirsia: I know one thing that it’s like you know, go to bed every day thinking I hope this device doesn’t get infected. If anything gives us gray hair, the bacteremias give us the gray hair. So as many one in 20 patients basically will have ICD implantable defibrillator or a pacer device infection over the next three years. So you implant the device today for the next three years, you tell patient, well, the risk of infection is always gonna be there. One in 20 and more than 60,000 patients actually develop an infection per year in this country. That’s the number. It’s a huge number. 

Dr. Aaron Dunn: Wow, that is a huge number. 1 in 20!

Dr. Andy Locke: One way that we try to reduce lead complications such as infection is to not put devices in people that really don’t need them. So that’s probably the best thing.

Dr. Shreya Trivedi: Yes, and this might be a good time spaced repetition back in pearl 1 where we talked about newer devices like leadless pacemakers or subcutaneous ICDs that would have a lower risk of device-related infection and maybe better for patients at higher risk of infection. 

Dr. Aaron Dunn: Classic Shreya Trivedi coming in with that spaced repetition. You are always putting those cognitive learning theories in action! 

Dr. Shreya Trivedi: I am very, very guilty – a huge nerd when it comes to that! Gotta make those connections

How to manage patients with a device who develop bacteremia

Dr. Aaron Dunn: Ok, with that in mind, let’s jump in and talk about how to manage patients with devices who develop bacteremia. 

Dr. Andy Locke: So any type of bacteremia we have to be involved, this commonly gets overlooked. And in fact, what we normally see is when we’re vetting these like, uh, MRI requests and infected patients that have devices, we usually say, Oh by the way, this patient was bacteremic with this infection, and they’re trying to figure out the, the source of the infection with the MRI. But we’re like, Oh shoot, we should be involved.

Dr. Aaron Dunn: I feel like I knee-jerk consult infectious disease in these types of cases, but I don’t always find myself reaching out to electrophysiology right away. And what we learned from our experts is that it’s wise to get both ID and EP involved early on.

Dr. Andy Locke: Taking out a device is a big deal. You know, I say taking out a device, like it’s easy, it’s a really big deal. Um, 1% risk of a serious complication, you know, having a crack chest or death. It’s never really an emergency, but it could be an urgency to get that device out.

Dr. Shreya Trivedi: Woah, 1% risk of a serious complication when removing a device. That’s much higher than I thought. 

Dr. Andy Locke: The thing that increases the, the risk of the device extraction when it’s transvenous is that these leads in the body actually fibrous to the veins and to the heart. So when you pull them out, you literally could lacerate or tear the, the superior vena cava, the right atrium, the right ventricle, you know, the, the IVC we sometimes perforate. 

Dr. Aaron Dunn: Ugh. Pacemaker extraction involves literally pulling out the leads that are fibrosed to patients’ vessels. That definitely sounds like a high bleeding risk! 

Dr. Shreya Trivedi: I can’t get out the image of the fibrosed vessels, and someone trying to take out leads from it! And so if it’s such a pacemaker extraction is such a big deal, do all pacemakers need to be taken out?

Dr. Andy Locke: So the way we think about this is, is, is there, so if there is bacteremia, does a patient have persistent bacteremia or uh, do they have bacteremia and now it’s better? In the case of persistent bacteremia, pretty much irrespective of the, bug, if you’ve dealt with the source, but you still have it, you have to assume the device is infected. So the device will have to come out.

Dr. Shreya Trivedi: Persistent bacteremia, device out and we are defining persistent as 2 or more days of positive blood cultures. What about transient bacteremia where maybe the cultures cleared the next day?

Dr. Andy Locke: In situations where a patient’s bacteremic, they have a source, you get rid of the source and they’ve cleared their cultures, it then comes down to what was the bug? There’s complex algorithms, but the way I think about it is, was this bug staph or not staph? Even if you’ve cleared bacteremia with staff, it’s so sticky. You have to extract the device, uh, because you will never get cure. Okay. Some strep species gram negatives. If you’ve had a, you have source control and you’ve had a good response maybe or maybe not extract the device fungemia you usually have to extract the device. 

Dr. Aaron Dunn: So the teaching point is that if the bacteremia clears quickly, the decision to remove the device or not is based on what is causing the infection – with things like staph aureus or fungi being more virulent and pushing the team more towards device extraction.

Dr. Shreya Trivedi: Right! And in addition to that, there are also patient factors, like whether or not they are immunocompromised or not which may also impact the decision. 

Dr. Aaron Dunn: But wait, one of my questions that came up with this is: what exactly happens if a device needs to get removed but the patient is dependent on that device? 

Dr. Shreya Trivedi: I am wondering about that, too. Some patients are 100% pacer dependent.

Dr. Andy Locke: We put a temp. You’ll hear the term temporary screw in lead or temporary screw in system. What that is it’s a real pacing lead that goes from the skin in, you know, into the vein. And we actually place it exactly how we would place a normal, uh, pacing lead. So I mean, you’ll see a dressing over it and that will provide someone with pacing until they have a re-implant. Typical duration is usually at least 72 hours. Or if there’s endocarditis or some other strange, you know, persistent infection, we can wait up to two weeks long.

Dr. Shreya Trivedi: Got it! So much learning happening here, I summarized the big takeaways, anyone who has bacteremia with an implantable device should probably have EP and ID involved early for the discussion on if pacemaker extraction is required, which is a huge deal and can carry 1% mortality. Persistent bacteremia with blood cultures positive for 2 days or more, that device definitely needs to be taken out. And transient bacteremia, if its staph or fungi, we’re more likely to be taken out because you assume pacemaker is seeding with those highly virulent bugs.

Pearl 5

How do you approach end-of-life care for a patient who has an implantable pacing device? 

Dr. Shreya Trivedi: Transitioning to our final pearl, probably the most important topic. We wanted to focus more on how to approach end-of-life care for patients with a pacemaker or ICD. 

Dr. Aaron Dunn: This question came up during one of my ICU rotations this year. A patient on the floor was actively dying and had transitioned to comfort measures only. They wanted to deactivate the ICD to prevent the patient from getting shocked. It was the middle of the night, and I tried calling cardiology but they were busy in the ED and not immediately available. 

Dr. Shreya Trivedi: So what did you do Aaron?

Dr. Aaron Dunn: Well, I was initially a bit confused about what to do. I asked around to find a magnet and then honestly watched a youtube video on how to deactivate the ICD. I was able to figure it out but I was worried about how to advise the patient and their family members, who were at the bedside, about what to expect when it was deactivated. And I had so many unanswered questions myself. How does the magnet actually work? How will the patient feel? 

Dr. Shreya Trivedi: Oh that all resonates. I feel I’ve had all those questions. 

Dr. Aaron Dunn: And just one thing we want to say upfront is yes, patients are going to make different decisions about whether or not they want their devices turned off at the end of life and ALL these feelings and decisions are valid. As a heads up, we are just trying to give example scenarios that might come up to help solidify our own frameworks on how these end of life discussions may be different in patients with different devices. 

Dr. Joshua Cooper: It is important to dive in deeper in terms of what the patient’s wishes truly are. Most people would agree that they don’t want to quote be a vegetable on a ventilator. And when people say they wanna be DNR, that’s usually the first thing that comes to mind. And most people are somewhat uniform in that regard. If there’s no chance for neurologic recovery, nobody would wanna be kept alive on a ventilator. But that’s very different from having ventricular fibrillation and being shocked back within 10 seconds and being exactly the same as you were right before with no neurologic or other consequences. And so if you were to describe to the patient what that would be like many patients who thought they would want their defibrillator turned off or they want to be DNR, say, oh, no, no, I, that’s okay.

Dr. Aaron Dunn: Hmm, I’ve never really thought about it that way. Even though a shock from an ICD might seem similar to other resuscitation efforts, it’s actually quite different, especially in terms of the patient’s risk of brain injury and chance of returning to their baseline. 

Dr. Shreya Trivedi: Yeah, getting shocked by an ICD after 10 seconds of Vfib is VERY different from undergoing multiple rounds of CPR, epi, amio, and all that. 

Dr. Aaron Dunn: But let’s say someone is dying and does NOT want shocks. How does that work? 

Dr. Joshua Cooper: Usually as somebody is passing, there is a risk that that person may go into ventricular fibrillation as a terminal rhythm, and they may get shocked at a time that that’s not what we would want. So typically we would want to turn off a defibrillator before the patient is fully passed so that their passing is as peaceful as possible and not punctuated by defibrillator shocks. Whether the patient is cognitively aware that it’s going on or family members are at the bedside and can see the body jolt, it’s not a pleasant experience and certainly not necessary. It’s important to recognize though that defibrillators can be deactivated without the need for electrophysiology, without the need for a programmer. A strong magnet that is placed over a defibrillator directly against the skin or the clothing will trip a magnetic switch in the defibrillator while the magnet is in place. That will basically turn off the detection of tachy arrhythmias and turn off the tachycardia treatments, including shocks.

Dr. Shreya Trivedi: Wow all you need is a strong magnet, as you learned Aaron, to turn off the shock function of the defibrillator. 

Dr. Aaron Dunn: Yeah a strong magnet and a good youtube or podcast clip.

Dr. Shreya Trivedi: So switching gears – how do pacemakers differ at the end-of-life?

Dr. Aaron Dunn: Yeah, I guess what I’m curious about is: does a pacemaker NEED to be turned off? 

Dr. Joshua Cooper: If a patient’s family or a patient requests that, then it’s important to educate them on that fact that really the pacemaker’s not gonna make a difference. And recognizing that a pacemaker cannot make a patient immortal, it will not be able to continue to keep the heart beating if other factors are not also going on. Meaning if the heart is starved for oxygen, if the pH falls below a certain level, if the potassium goes, rises above a certain level, then the heart muscle starts to die. And you cannot keep that heart muscle alive simply by pacing it. And so in patients, for example, who are extubated in an ICU setting or who have severe hypotension despite maximal pressors turning off the pacemaker will in no way meaningfully change that patient’s remainder of that patient’s life or leaving it on likewise will have no meaningful effect. If they’re dying, they’re dying from hypotension/ischemia to the heart, the heart muscle will die. And the pacemaker, although it will still deliver electrical pulses, will no longer be able to keep the heart beating. You will see pacemaker spikes with no QRS complexes, no heartbeat going on. And so in most scenarios of end of life turning off a pacemaker does not really play a role.

Dr. Aaron Dunn: That’s an important learning point that pacemakers do not NEED to be turned off when a patient is dying. But what would happen if a patient asks for it to be turned off? Can we even do that?

Dr. Joshua Cooper: If a pacemaker were to be turned off, meaning you literally turn off the pacing functions, then what would then happen to the patient would depend on how much they rely on that pacing. If they pace on rare occasions, then there would be no immediate effect. If they pace all the time but their underlying heart rhythm is just slow in the thirties or twenties, then they’re not gonna pass away when you turn off the pacemaker. But they’re gonna feel lousy, they’re gonna feel lightheaded or faint or nauseated or weak, and they may suffer more by turning off that pacemaker because it’s actually palliative for them to have a heart rate of 60 as opposed to 25. If they are pacemaker dependent, meaning they have a heart rate of zero when you turn off the pacemaker, then they will pass away immediately because they’ll have no heartbeat. That does raise for many physicians or healthcare providers some ethical concerns because they would equate that interaction with physician assisted suicide. And there have been many ethical committees and discussions and publications about this, about what is the difference, if any, between an implanted pacemaker that’s keeping a person alive and a ventilator that’s keeping a person alive because they’re very different in terms of how we perceive them. A pacemaker may have been implanted for 10, 15, 20 years, and it’s invisible to the eye because it’s under the skin and it’s internal. In fact, we almost consider it incorporated as part of the patient, but it is an electrical man made device that is keeping the patient alive. It’s just not visible. A ventilator is obviously much more visible and much more invasive in a way. I’ve myself personally evolved in my thought process. I was very uncomfortable early on in my career with the concept of turning off a pacemaker in somebody who requests it. And I, I’ve evolved over time to recognize that it truly is an artificial means, even though it may have been present for a long time of keeping somebody alive who’s pacer dependent. And I have, in fact, on a couple occasions, turned off a pacemaker in a patient who requested or whose family members requested. One notable example was a patient who had a massive stroke, a devastating neurologic injury, but whose organs were fine, his heart was beating, his kidneys were functioning, he was breathing on his own, he was not intubated, he was lying there in bed breathing fine, but he had no cognitive function left because of a devastating stroke and was in bed, and who knows how long he would live. The family decided, first of all, to not put a feeding tube in and not feed him, but in addition, he was pacemaker dependent and they requested the pacemaker be turned off. And that is something that I did after a long discussion with the family.

Dr. Shreya Trivedi: What a profound story. There’s just so much in there.

Dr. Aaron Dunn: Yeah. It’s really helpful to hear about how his thought process has changed on this issue. What are you taking away from this, Shreya?

Dr. Shreya Trivedi: Yeah, one take away I have is that a patient’s end-of-life situation with a pacemaker will vary a lot, so one thing I should think about why they have the pacemaker, what the pacemaker is doing for them and how dependent they are on. What about you Aaron, what are you taking away?

Dr. Aaron Dunn: What I’m coming away with is that pacemakers actually do NOT need to be turned off, in fact it will likely make patients worse due to a slower heart rate. But if turning off the pacemaker is in line with their wishes, it’s best to loop in ethics or palliative care to help with that complex decision making. And then lastly, with ICDs, we can use a magnet to turn it off so the patient doesn’t feel shocks at the end of life. 

Dr. Shreya Trivedi: And with that end of life discussion, we are at the end of the episode!  If you found this episode helpful, please share with your team and colleagues and give it a rating on Apple podcasts or whatever podcast app you use! It really does help people find us! Tweet us and leave a comment on our website, or on instagram or facebook page. Thank you to Dr. Pamela Tung and Dr. Saima Karim for reviewing this episode. Thank you also to Daksh Bhatia for audio editing and to Dr. Cathy Cichon for the accompanying graphics. 

Dr. Aaron Dunn: This episode was made as part of the Digital Education Track at BIDMC–thank you to all our great educators and mentors!

Dr. Shreya Trivedi: As always, we love hearing feedback. Email us at hello@coreimpodcast.com. Opinions expressed are our own and do not represent the opinions of any affiliated institutions.


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