Welcome everyone to the Programming Basics module of our course. My name is Amber Seiler and I'm excited to share this information with you today. These are my disclosures. If you remember from our interrogation module, we spent a lot of time looking at the information within a patient's device that could be evaluated either in the clinic or through remote interrogation. Today we're going to spend time on programming and how these interplay together. Our objectives for this course are going to be to understand basic programming concepts, evaluate patient needs and customize programming to meet those needs, and understand some advanced programming features. This module is designed to build off of our interrogation module and also the device technology modules that you've already been through. Because this is a lot of information, we are going to separate this into two different sections, just like the interrogation module. So let's talk through programming. There are three big buckets that we want to discuss today. The first is device testing, followed by in-person device programming, and then remote alert programming. These are all separate programming options that we have with our patients and they're all important to think about separately as we evaluate our patients and where we're seeing them. So let's start with device testing. As you remember in interrogation, we talked about sensing quite a bit. So this is going to be how we evaluate sensing manually through a programmer. As a reminder, sensing is the evaluation of what the device is actually seeing from the tip of the lead. So in order to test for sensing, we have to do a couple of things. The first is there has to be intrinsic events faster than the lower programmed pacing rate, or we have to manually lower the rate that the device is pacing at to allow for those intrinsic events to come through. So let's think about that a little bit more. Sensing, as we reviewed before, is the ability of the pacemaker to see when a natural depolarization is occurring. Pacemakers sense these depolarizations by measuring changes in the electrical potential of myocardial cells between the anode and the cathode. Dr. Allred reviewed that in depth with his previous modules so we won't go into that again here, but it's worth reviewing if you didn't understand that concept completely. So here's a couple of examples of sensing signals. So the first is a 0.5 millivolt signal and the second is a 2 millivolt signal. And you can see a pretty significant size difference in those deflections. As we think about pacemakers and defibrillators and how they are able to sense intrinsic rhythms, what we want to do is be sure that they're able to capture every intrinsic rhythm that comes through and not see things that aren't true intrinsic deflections. So when we think about those true intrinsic deflections we're thinking about our P waves and our QRS complexes. Those are really the only two signals that we want for our devices to see and so we want to make sure that we program our sensing to where we're able to capture that data and not see other things like T waves. So when we look at acceptable sensing values for the atrium so these again are our P waves, acutely we want our P waves to be greater than 1.5 millivolts and chronically we want our P waves to be greater than 1 millivolt. For our ventricle which are our R waves, we want our acute R waves to be greater than 7 millivolts and we want our chronic R waves to be greater than 5 millivolts. And if you remember again when we talked last time about interrogation, if you think about a newly implanted lead, all of the inflammation around that lead tip and then also the scar tissue that's subsequently going to form we want to make sure that we have a big enough safety margin there so that we can see things as that scar tissue forms and that's the reason that we want our acute values to be a little bit higher than we're willing to settle for in our chronic values. So as we think about this, this is an example of a cardiac complex. So we have our P wave, our QRS and then our T wave and these are some examples of average voltage so you can see there on the right hand side voltage, so 1.25 2.5 and then 5 volts and you can see where our cardiac signals fall in that tracing. So for example, if we had a patient and their lead was in their right ventricle, which meant that we wanted to capture that R wave we want to make sure that our sensing threshold was able to capture something that was a little bit over 2.5 millivolts. Let's look at that in a little bit of a different way. So if we have our sensing number, so our sensitivity programming set at 5 millivolts for example and I want you to think about this as a fence because this gets a little bit confusing. Then we wouldn't see anything. So you can see that our fence is completely covering up our P wave, our R wave and our T wave. So we would see nothing at all within that cardiac cycle. This gets interesting as you talk to your physicians and to your device colleagues about how sensing is programmed because the less sensitive a device is the higher the sensitivity number, which is a little bit counterintuitive. And so if you say I'm going to decrease their sensitivity then that means that you're actually going to increase your sensitivity number that you're programming within the device. So as you're talking about sensing with your colleagues and also with your physicians that's just important to keep in mind so that everyone's on the same page as to what you're actually programming within these devices. So here's another example where we've lowered our fence significantly so we've made our device more sensitive by decreasing our sensitivity number. And what you can see here is that we are able to see our R wave but we're also able to see our T wave. And if you remember the two things that we really want to be able to capture here are our P waves and our R waves. We don't want to see our T waves because if you remember from interrogation if we see T waves the device counts that as an intrinsic signal and says that was an R wave. You told me to look at that. And so I'm going to reset my timing cycles and reset my counters and everything else that I do and behave off of based off of that signal. So this sensing would be too low and we would want to make sure that we raised our fence a little bit to cover up that T wave. So this would be adequate RV sensing. So we're able to see our R wave. We are not able to see our T wave or our P wave. So this would be kind of an ideal sensing setting for this patient. So whenever we think about sensing and sensing amplifiers it's important to understand how a device sees these signals and how they're filtered out. So all pacemakers and defibrillators filter out these extraneous signals that the device is receiving because again whatever a patient senses is by definition a P wave or an R wave. And so the devices use amplifiers that have filters to allow appropriate sensing of only P waves and R waves and reject those inappropriate signals. Some of those most common unwanted signals like we talked about last time are T waves. Again the pacemaker is going to define that as an R wave, reset counters, reset intervals, all of those things which can be detrimental to our patients because we may not pace when we need to. Far field events which can be R waves that are sensed by the atrial channel which the pacemaker thinks are P waves and if you remember back in our interrogation module we had that example where on the LV channel we were actually seeing flutter waves from the left atrium. That was kind of opposite of this example but the same concept there is true. Skeletal muscle myopotentials like from the pectoral muscle which the pacemaker might think are either P or R waves. And if you remember we had that example whenever we talked about a patient who might have an insulation problem and they had noise on their lead that could be replicated by doing isometric exercises. And then the pacemaker can also see signals that are actually from the pacemaker itself so for example a ventricular pacing spike that was sensed on the atrial channel which is defined as crosstalk. And I know that Dr. Auert reviewed blanking periods and all of those things and that's where a lot of this comes into play. So pacemaker and defibrillator manufacturers understand that the signals the device is putting out can be seen on opposite channels which is why they've built in those blanking periods to try to minimize that effect. I want to spend a few minutes just talking about vectors and how a device actually sees this information when it comes in. So the wave of depolarization that's produced by normal conduction creates a gradient across the cathode and the anode. And that changing polarity is what actually creates that signal. So when that signal exceeds the program sensitivity or our fence that's when it's sensed by the device. So if there were a signal coming in that perhaps was not aligned with that lead or came at the lead from a different direction we could expect that our sensing value would be different based off of where the vector and where the gradient is in relation to where the lead is placed. That can affect our sensing program and also our patient's ability to see those intrinsic signals and then adequately pace or inhibit pacing off of what it sees. So here's a really good example. And we talked about this in interrogation also a little bit. Let's say we have a PVC that occurs which is conducted abnormally, meaning it doesn't go through the normal conduction system pathway. So since the vector relative to that lead has changed, what effect might that have on sensing? So if our device's lead is in the right ventricle and we're used to seeing our cardiac signals originating from the right ventricle and then we have a PVC that perhaps originates from our left ventricle, then we could anticipate that that PVC could either have a higher or a lower sensing amplitude than our normal intrinsic R wave. So in this example, where the PVC is coming more from the left ventricle the wave of depolarization strikes the anode and the cathode almost simultaneously, which creates a smaller gradient and thus a smaller signal, which our device may not see. So what things can affect sensing accuracy? Our pacemaker circuit, which is our lead integrity, insulation breaks or wire fractures can certainly affect our sensing accuracy. If you remember our insulation breaks, we would be concerned more about noise or over-sensing of myo-potentials. Wire fractures, we would be concerned about noise, but in a different way. This would create make-break signals within that lead, which the device could see as ventricular events. The characteristics of the electrode can also affect sensing accuracy. Electrode placement within the heart, this is especially important now that his bundle pacing and left bundle pacing are becoming more prevalent. Our devices now most commonly are not implanted with their right ventricular lead at the RV apex, they're oftentimes implanted much higher on the RV septum, which can affect sensing and our sensing values. The sensing amplifiers of the pacemaker, lead polarity as we've discussed before, whether or not the lead is programmed unipolar or bipolar, EMI, which for example is something that the patient might have externally that the device is able to pick up. So a really good example of this is an MRI scanner or there are some household items that also can cause interference with your patient's devices. It's really important to understand what those are and each manufacturer has pretty specific recommendations on what patients should stay away from and so I'm not going to go into that today because it really is a little bit manufacturer specific. What's important for you and for your patients to know is that devices and their filters have gotten a lot smarter and so it really is pretty rare that household items are going to interfere with your patient's implanted device as long as they're in good working order and well maintained. So let's think about undersensing. So if a pacemaker doesn't see the intrinsic beat and therefore doesn't respond appropriately, which in this case would be by inhibiting pacing, then what you get is overpacing. So this is again a little bit counterintuitive but undersensing always equals overpacing. We have inappropriate pacing because that R wave was not seen. So let's orient ourselves a little bit to this strip. So we have at the top an EGM it looks like a surface EGM because we're able to see P waves and our QRS complexes and then underneath there we have a marker channel. So we can see that we're V pacing on this strip. We can also see that whenever there's an intrinsic R wave, a V pace follows, which means that the device did not sense that R wave or it was told not to as we talked about before in our pacing modes. Most of the time we have our devices programmed where we do want them to see and pay attention to any intrinsic signals that occur and so for this patient I would say we need to lower our fence so that we can make sure that we're seeing those intrinsic signals as they come in and prohibit inappropriate pacing. Here's another example. This one is the opposite where oversensing equals underpacing. So it's where electrical signals other than the intended P wave or R wave are detected and so again to orient ourselves to this strip what we can see is a surface EGM at the top and we have our marker channels at the bottom. So we have a V pace complex as our complex number one that captures. A second V pace complex that captures. Then we have a P wave. Our R wave actually is detected there and then our T wave and then what you can see is we have these V sense markers that don't align with any intrinsic cardiac activity. So what we can interpret from this strip is that the device is seeing something but the device is not seeing R waves or P waves and so this would be a really important time to look at your intracardiac EGMs to evaluate what the device is seeing. Is it myo-potentials? Is there some noise on that lead? And then evaluating how we can program around that to make sure that we're not over-sensing, because that does lead to underpacing. And you can imagine in a pacemaker-dependent patient that this could be very problematic, because they wouldn't have their intrinsic R-wave. So let's take a break here and just think through this question. So which of these pacemakers is more sensitive? So pacemaker A has our program sensitivity at 0.5 millivolts, or pacemaker B has our program sensitivity at 2.5 millivolts. Remembering that our program sensitivity is our fence, and more sensitive is the lower the number. So our pacemaker A is actually going to be more sensitive, because we're telling that device, I want you to look at more signals. So we've talked through sensing. Now it's time to talk about thresholds. And again, we talked through these quite a bit on the interrogation module. What we can learn from thresholds are safety margins, all of the things that we're looking for as we're looking at our thresholds. But let's talk about threshold testing and how this is measured. So thresholds are measured in voltage. And voltage is the force that causes the electrons to move through a circuit. So in a pacing system, voltage is measured in volts, and that's represented by a capital V. And it's provided by the pacemaker battery. And it's often talked about as the amplitude or the pulse amplitude of the threshold. It is important to note that depending on who you're speaking with and how long they've been in this business, some people might say amplitude, some people might say voltage. They are often used interchangeably. I would say voltage is probably the more common terminology that's used. You can't go wrong with either one, though. So what is a capture threshold? So a capture threshold is the minimum electrical stimulus needed to consistently capture the heart outside of the heart's own refractory period. So if this is a threshold strip and we're programmed to pace at 60 beats a minute, again, we've got our surface EGM at the top. We know that because we can see P waves here. At the bottom, we have our marker channels. So our first complex is a V-pace complex that captures. Our second is another V-pace complex that captures. Same with the third. The fourth complex there, we have a V-pace, but no ventricular capture. And then the patient's intrinsic R wave comes in on its own. So what we can say is that we don't have capture of that fourth complex, but we do have consistent capture of the three V-pacing complexes before that. I want to make a quick comment here about the P waves and how they don't seem to have any relation at all to the QRS complexes or the V-pacing. And that's exactly right. They don't. So in all of these examples so far that we've looked at, the device has been programmed BVI. And so if you remember from our interrogation module, that means that we're pacing the ventricle, we're sensing the ventricle, and we're inhibiting pacing based off of an intrinsic complex. So the device is not paying any attention at all to any P waves that might be present. Sometimes that can be confusing because you're like, wait a minute, there's a P wave there. Why are we not timing off of that? But that's why it's important to know how your device is programmed and how you're telling the device to behave. So let's think through some factors that can affect our pacing thresholds. Again, our lead integrity there always, always is an issue. The characteristics of the electrode also can affect our pacing thresholds. Electrode placement within the heart, same as sensing. Drugs, either illegal or prescribed, can affect our pacing thresholds. Electrolytes certainly have a play here, just like they do on any part of our cardiac cycle. And sleeping and eating can also affect our pacing thresholds. And so as you remember before, we talked a lot about why it's important to have a safety margin for not only sensing, but also thresholds. All of those same reasons are still true today. So let's think about myocardial capture. So capture is a function of two different things. We've talked about amplitude, which is the strength of the impulse expressed in volts. And the amplitude must be large enough to cause depolarization or capture the heart. And the amplitude must also be sufficient to provide that appropriate safety margin. There are two pieces, though, of our threshold. If there's amplitude, and then there's also pulse width. So pulse width is the duration of the current flow expressed in milliseconds. And the pulse width must be long enough to cause depolarization to disperse to the surrounding tissues. So if somebody tells you that a patient's threshold is 0.5 volts at 0.4 milliseconds, we know that the 0.5 is the amplitude of that impulse, and the 0.5 milliseconds is the pulse width of that impulse. So here's a comparison. So if we have an amplitude of five volts, we can program that at different pulse widths. So we could have 0.5 milliseconds, 0.25 is certainly narrower, and then one millisecond is longer. An important thing to know here is that most commonly, pulse widths are going to be 0.4 or 0.5 milliseconds. That's kind of industry standard, and where most devices are programmed out of the box or nominally. There are some reasons where you might want to extend a patient's pulse width. So let's think about this, for example. If we have a patient whose capture threshold is a little bit higher than what we might like. So let's say their capture threshold is 1.5 volts at 0.4 milliseconds. We've talked about before that we want our safety margin to be two times our voltage. So that would mean our voltage or our programmed output would need to be three volts at 0.5 milliseconds. But you also remember that we talked about how output can have a really big effect on our battery. Anytime that we go above two and a half volts in output, we worry about accelerated battery depletion. So if your patient's threshold was 1.5 volts at 0.5 milliseconds, you might be able to get them down to 1.25 volts or even one volt if you extend their pulse width. So in practice, that's when I would most commonly extend pulse widths, is if my threshold was higher than 1.25 volts in amplitude, and I knew I was gonna have to go above that 2.5 times output in programming, I would oftentimes see if extending the pulse width could decrease our amplitude and help to save on our battery longevity. So our primary goal for programming thresholds is to ensure patient safety and appropriate device performance. Patient safety is always number one, and your physicians might have different takes on what an appropriate safety margin is. So in the RV, one might argue the most important safety chamber for the heart. They might want a two-time safety margin for that chamber. But your LV lead, where we know thresholds can be higher, and we also have things to contend with, like diaphragmatic stimulation, they might be willing to accept a smaller safety margin in order to preserve battery and also promote patient comfort. Our secondary goal is to extend the service life of the battery. Again, that amplitude of 2.5 volts is really what we wanna stay at or below, but we always want to maintain adequate safety margins. It's never okay to have less of a safety margin to try to preserve battery, unless your physicians are aware and understand what's going on with that patient and have made that decision. Amplitude values greater than the cell capacity of a pacemaker battery, usually that 2.8 volts, do require a voltage multiplier, and that voltage multiplier is what decreases our battery longevity, sometimes markedly so. Okay, so let's look at this strip and think about what this threshold is. So at the top here, we've got our surface electrogram, and again, my encouragement to everyone learning devices is to make sure you're hooking every single patient that you interrogate in the office up to a surface electrocardiogram. This is gonna give you a frame of reference and give you a foundation to stand on and something that you're actually used to looking at. Our second line is our marker channel, and that's telling us what the device is seeing or what the device is doing. And then our third line there is gonna be our RV intracardiac electrogram. So we know this is a pacing threshold strip because we can see voltage here at the top, and we're walking down. So that's what tells me, okay, this is a threshold testing strip. So a patient's in the office sitting in our chair and we're actually testing to see what the capture threshold is on this device. So you can see they start off at 1.25 volts. You get a series of pacing complexes, and then we decrease the voltage to one volt, series of pacing complexes decrease again to 0.75 volts, and then finally decrease to 0.5 volts. What we notice at the 1.25 volts is that we do have consistent capture. So you can see your V pacing on your marker channel. You can see that pacing spike, not only on the RV electrogram, but also on our surface electrogram. And then we can see our depolarization there because we have a QRS complex. And that's consistent across all of those complexes there at 1.25 volts. At one volt, we have capture with those first two, maybe three pacing complexes, depending on where you wanna start your one volt. But then if you notice the fourth pacing complex there, so we have V pace on our marker channel, but no QRS that corresponds to it, which tells us that we lost capture at one volt. We did get it back again at the change over there to the 0.75 volts, and we actually got capture at one of the beats of 0.75 volts. But if you remember our definition of our pacing threshold is where we can consistently capture the heart. So as soon as you lose any, any, any pacing complex, we have lost capture. So here I would say we lost capture at one volt, which means that our threshold is 1.25 volts. Okay, so we've talked about sensitivity. We've talked about output, which is again, are our thresholds. Let's talk through pacing modes here just for a few minutes. And we reviewed this in our prior lesson, but it's important to revisit it because this can be very, very, very confusing for folks as they're looking at how devices are programmed. I want to encourage you as you're looking at how devices are programmed, either as patients are in clinic, or if you're just reviewing a interrogation report, think about these things really systematically. So if you see something that says DDDR, I want you to think to yourself, okay, we are pacing the atrium and the ventricle. We are sensing the atrium and the ventricle. We are triggering and inhibiting pacing based off of sensing and rate responses programmed on. It seems silly to break it down that simply each time, but it's really important to do that in your head because it matters so much in interpretation of electrograms, when you're speaking with your patients about how they're feeling, all of those things. So I would encourage you to just slow down, think about these as you go through them very systematically. So here's a few examples. Let's walk through these together. So if a patient's programmed DDD, that means again, we're pacing both the atrium and the ventricle, we're sensing both the atrium and the ventricle, and we are both triggering and inhibiting pacing based off of that sensing signal. Another example, if a patient's programmed BVI, like we saw on that strip, which was a great example. So we're pacing the ventricle, we're sensing the ventricle, and then we are inhibiting pacing based off of that response to sensing. And that explains again why, yes, there were P waves present, but we have told the device, I don't want you to pay any attention to any P waves or any atrial activity. And so therefore they weren't taken into account. If that patient that we looked at before had a dual chamber device, I would consider reprogramming that device to DDD or DDDR depending on the patient's need for rate response. So let's walk through a few more examples. So what does VVIR mode mean? So again, I want you to think to yourself, where are we pacing? We're gonna pace in the ventricle. Where are we sensing? We're gonna sense in the ventricle. The I means that we're gonna inhibit pacing based on our response to sensing. And then R means that rate response is programmed on, which means the device is actually gonna help augment the patient's heart rate based off of sensor information it's receiving from within the pacemaker. Same thing with DDIR. So if they're programmed DDIR, again, that first letter is where are they pacing? Atrium and ventricle. Second letter is where are they sensing? Atrium and ventricle. The I means that we're gonna inhibit pacing based off of a sensed event. And then R again, rate response is programmed on, which means we're gonna augment the patient's heart rate based off of sensor information from the device. So if a patient has frequently undersensed atrial arrhythmias, which pacing mode would be most appropriate? And I recognize that's a little bit of a trick question. I probably haven't given you all the information that you need to answer it. But what we know are a few things. One, we know they have atrial arrhythmias, so atrial fibrillation or atrial flutter. We also know that if a patient has atrial arrhythmias, we don't necessarily need to pace the atrium unless those arrhythmias are either paroxysmal or persistent, but they have some intermittent sinus rhythm. We also know that if they have undersensing of atrial arrhythmias, we have concern there for overpacing. So in this situation, most commonly what I see is a patient that has gone into permanent atrial fibrillation. The device is not always sensing those AFib signals because they're gonna be much, much, much smaller than a normal P wave. And so most appropriately, what I would do there is program this device to VBIR. So we're gonna tell the device, you know what? Don't even look at the atrial chamber. We know that they're in permanent atrial fibrillation and we don't need to pay attention to it anymore. Another option would be DDIR, which would still allow for pacing and sensing of the atrial chamber if needed, but that we would inhibit pacing based off those signals. Or you can even do VDIR, which means we're only gonna pace the ventricle, which would obviate any atrial overpacing that might have occurred. I know that was a lot of information. And so we're going to pause here and conclude part one of our programming basics module.

Amber Seiler

Programming Basics

Medical Devices

Patient Needs Evaluation

Device Testing

Pacemakers

Pacing Modes