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Pacemaker Troubleshooting Module 9

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1 Pacemaker Troubleshooting Module 9
Student Notes In Module 9 we’ll discuss Pacemaker Troubleshooting, and provide a method to use when evaluating device malfunction, in order to help arrive at a diagnosis and the most appropriate intervention. It is possible that you may require additional supplemental materials to enhance your knowledge or provide more practice. If you feel this is necessary for you, ask your instructor for suggestions on books or other tools. Instructor Notes This module should take approximately 2 hours to cover. To deliver this module the following materials are suggested: Printed Participant Guides for each participant Overhead projector and screen Optional: Whiteboard or flip chart While delivering the module, engage the learners by asking questions and getting them to talk based on their previous subject knowledge. Evaluate the learners by delivering the knowledge check at the end of this module. An acceptable score is 90%. World Headquarters Medtronic, Inc. 710 Medtronic Parkway Minneapolis, MN USA Internet: Tel: (763) Europe Medtronic International Trading Sàrl Route du Molliau Ch Tolochenaz Switzerland Tel: (41 21) Asia-Pacific Medtronic International, Ltd. 16/F Manulife Plaza The Lee Gardens, 33 Hysan Avenue Causeway Bay Hong Kong Tel: (852) Canada Medtronic of Canada Ltd. 6733 Kitimat Road Mississauga, Ontario L5N 1W3 Tel: (905) Toll-free: 1 (800) Medtronic USA, Inc. Toll-free: 1 (800) (24-hour technical support for physicians and medical professionals) Latin America Medtronic USA, Inc. Doral Corporate Center II 3750 NW 87th Avenue Suite 700 Miami, FL 33178 USA Tel: (305) UC d EN Medtronic, Inc. Minneapolis, MN February 2008

2 Objectives List steps in performing troubleshooting
Correctly identify the following on an ECG strip: Pacemaker ERI behavior Loss of Capture Over- and undersensing Magnet behavior Pseudo-malfunctions Make clinically appropriate suggestions based on interpretation Identify additional information or other resources useful to diagnosing pacemaker malfunction Student Notes The objectives are listed here. Instructor Notes

3 Some Good Advice Perform all troubleshooting and all pacemaker checks the same way Collect the data Ask questions Keep an open mind Analyze, form hypothesis, test Don’t make assumptions The simplest explanation that covers all the facts, is usually the correct explanation Student Notes Pacemaker or troubleshooting checks on any device is really nothing more than performing a routine follow-up. The difference is only that in the case of “troubleshooting,” someone suspects a problem, and during a routine follow-up, no problem is suspected. So, in both cases, assumptions are being made. However, if you approach every follow-up and every “troubleshooting” using the same method, you’ll decrease the possibility that you will miss something important, and increase the likelihood that you will be providing a valuable service to both the customer and the patient. The customer will recognize the value of the services you do provide. Instructor Notes Use this advice to emphasize the importance of learning a process for performing follow-up and troubleshooting, and to document the steps you take in the patient’s medical record.

4 The Four Solutions to Pacemaker Problems
Re-Program – the device Re-Place – the system or a component Re-Position – the lead(s), the device Retreat – do nothing, because nothing is wrong Student Notes Fundamentally there are really only four solutions to problems presented by malfunctioning pacemakers. The suggestions you make will be based on implementing some combination of these solutions. However, the process you use to arrive at a diagnosis and suggestion, or intervention, is paramount. Instructor Notes The four basic solutions to pacemaker malfunction.

5 The Process Observe/collect data Form your hypothesis
Measure the ECG (e.g., A-A, V-V, A-V, V-A) Form your hypothesis Test your “solution” Make a suggestion Ask the clinician questions Student Notes As you become more experienced at pacemaker troubleshooting, you may be tempted to mimic someone with whom you have worked with. When one is well experienced in troubleshooting, and follow-up seems to effortlessly identify and solve problems, you may be tempted to act similarly. However, skills are based on applying a method, over and over, until they become so proficient they look like they are solving the problem reflexively. Understand that device troubleshooting, and follow-up takes practice. In the rest of this module we will describe and apply a process for pacemaker troubleshooting, drawing on all the information and skills you have learned in the previous modules. We will demonstrate the application of a troubleshooting process, and then guide you through subsequent examples. Instructor Notes One process, and the one that we emphasize here.

6 Data Sources Programmed parameters Patient symptoms Medical history
Indication for implant Implant date Rhythm strip Device model number Lead model numbers Telemetry data Impedances Battery voltage Marker Channel™ Device diagnostics Device RRT and EOS behaviors Student Notes The first step is always to collect data. Many times the cause and solutions to pacemaker problems are suggested by a simple data point – for example, a very high lead impedance. At other times the data are more obscure, requiring examination of collected ECGs, investigation of patient complaints, review of collected device diagnostics, etc. During this step, try to collect the data you think you’ll need without rushing to a conclusion. Over time you will get better at intuiting what is important from what is not needed. Instructor Notes Data collection, especially asking the right questions, is almost an art form. Practice makes perfect.

7 Case 1 Information you have: Click for Hint
DDD PAV/SAV ms PVARP 310 ms Question: Why is rhythm irregular, sometimes fast? Hypotheses: Tracking PAF Oversensing (tracking a “P-wave” that is not there) Are these grouped beats – upper tracking rate behavior? Click for Hint Student Notes Let’s walk through an example. By this point you should know how to interrogate a device and measure ECG intervals. Here we have an ECG from a DDD pacemaker, with the parameters listed. Usually, where we all get stuck is forming a hypothesis. In other words, “I know how to run any test, I just don’t know which test to run NOW.” Let’s look at this ECG and try to think of reasons that would cause it to be so irregular. Some reasons that should come to mind are: An atrial arrhythmia is present and the device is tracking it Atrial oversensing and the device is ‘tracking’ it Upper rate behavior – Wenckebach – grouped beats Instructor Notes Guide students through this example by asking questions and eliciting discussion. The solution may be easy to some, and it may be volunteered early, even upon just looking at this slide. This is a perfect opportunity to ask the person who volunteered the answer how they arrived at their answer. If it was a lucky guess, use it as an opportunity to talk about the process. If they have a process, ask them to explain it.

8 Case 1 First Hypothesis: Tracking Paroxysmal AF
What is the evidence for AF? Irregular ventricular events Could be “fine” AF, not visible on baseline What is the evidence against AF? Some visible P-waves Evidence of atrial pacing Student Notes One hypothesis is that the device is tracking PAF. What evidence supports or argues against this? Evidence supporting tracking PAF: Ventricular response is irregularly irregular Variable P-waves Evidence not supporting PAF tracking: Evidence of atrial pacing Instructor Notes Take the learner step-by-step through the various hypotheses to evaluate supporting and opposing evidence. This is part of the data analysis step.

9 Case 1 Second Hypothesis: Atrial Oversensing
What is the evidence for atrial oversensing? Irregular ventricular tracking Evidence of ventricular tracking without visible P-waves What is evidence against atrial oversensing? There may be P-waves “hidden” in some T-waves Student Notes A second hypothesis is that we are witnessing atrial oversensing during which “oversensed” P-waves are tracked. Supporting evidence: Irregular ventricular tracking – the oversensing is irregular as well Evidence of ventricular tracking without visible P-waves Evidence arguing against atrial oversensing: Perhaps some P-waves within T-waves Instructor Notes

10 Case 1 Third Hypothesis: Upper Rate Behavior
What is the evidence for Wenckebach? Some evidence of “grouped” beats Evidence of P-waves “hidden” in some T-waves What is evidence against Wenckebach? The A-A intervals don’t march out Evidence of atrial pacing – no need if this is UTR behavior Student Notes A third hypothesis is upper rate behavior. Supporting this: We do see some of what appear to be grouped beats Perhaps there are P- waves in some T-waves Arguing against this: A-A intervals do not march out We see atrial pacing – this is not needed if the patient is in sinus tachycardia unless there was also intermittent atrial undersensing, and there is no evidence of this at all Based on this evidence, do you agree that it is unlikely that the “problem” is merely pacemaker Wenckebach? Instructor Notes

11 Case 1 What Are Your Next Steps?
To form a better hypothesis: Interrogate pacemaker Observe ECG and Marker Channel strip To test the hypothesis: Perform sensing test – observe rhythm/markers Check lead impedance for low impedance (insulation break), which often causes oversensing (< about 250 Ω) What is the normal impedance range (assume standard leads)? Student Notes So this situation is either: True AF with tracking, or Atrial oversensing with inappropriate tracking How to make the differential diagnosis? Marker Channel annotations would be very helpful, in fact, definitive. What else would help? Suppose you obtained a low atrial impedance reading? What would you then suspect? Suppose a sensing test returned very large P-waves, but were programmed to a very sensitive value? Instructor Notes Now we will test the two likely hypotheses.

12 Case 1 Final Hypothesis: Arial Oversensing
Confirmed by Marker Channel annotations showing AS markers without P-waves Student Notes Marker Channel annotations confirm atrial oversensing. Obviously, this is a tool that can make you look very smart. Instructor Notes This is our conclusion: Atrial oversensing.

13 Case 1 Conclusion: Arial Oversensing
What do you consider? The “service” you provide to the customer is not in just interpreting pacemaker behavior You are there to supplement the customer’s clinical knowledge and experience with your knowledge and experience regarding the pacing system If the customer asks, you have to be ready to make an appropriate suggestion Ask questions Find out the relevant concerns that the customer has for this patient If you are uncertain, call Technical Services Student Notes OK, now the hard part, what do you consider – assuming you are asked? This is really the point – being able to diagnose a problem is satisfying, but the customer may ask you: “Well, now what should I do about this?” Again, when observing experienced staff or working with long-standing customers, the process is often abbreviated. The rep may just give a suggestion based on long experience with the issue and the customer. Your best bet is to ask some questions first, and discover some solutions with the customer. Instructor Notes However, we are not necessarily finished.

14 Example Case 1 Conclusion: Arial Oversensing
Cause Insulation breach Bipolar impedance: 190 Ω Student Notes Let’s keep using this case. Suppose we diagnose the problem as atrial oversensing because of an insulation breach. The definitive “fix” is to replace the lead, but is that always the best solution? A less invasive solution could be to program the lead to unipolar, and then test to determine if this will work. Several serial impedance tests would be in order, as would provocative testing. If the fix were this easy and involved so little risk, the suggestion is easy. But jumping to it – as a long term solution anyway – might not satisfy the customer. For example, suppose you later found out that the patient was scheduled for a device upgrade. Would that change your suggestion that re-programming is the “solution.” Instructor Notes

15 Example Case 1 Conclusion: Artial Oversensing
Considerations: How easy is it to “fix” Unipolar lead in situ What are the risks to the patient to “fix” Elderly, debilitated patient What are the risks/implications if it is not “fixed” Loss of AV synchrony Possible that AF diagnostics are not accurate Risk of PMT Are there any alternatives? VVI? Student Notes Suppose it is more complicated. Let’s say the lead is already unipolar. Your choice then is: To accept the oversensing To replace the lead To reprogram the pacemaker to VVI Again, the definitive fix is replacement. But before you suggest this unequivocally, it might be wise to at least ask: What are the risks to this patient if he is re-operated on? Compare that risk to the risk of programming VVI Ultimately, the decision is up to the physician, the patient, and the family, but your job is to supplement the customer’s clinical knowledge and experience with your own knowledge and experience, regarding the pacing system. Instructor Notes

16 Example Case 1 Conclusion: Arial Oversensing
Cause Unknown Other resources Medtronic Technical Services (within the U.S.) Medtronic Product Performance Report There may be an issue with a particular Medtronic product you are not aware of Other manufacturers do not necessarily produce these reports Your colleagues Student Notes Finally, sometimes there is no “right” answer, or there are a lot of different answers, all with risks and benefits. Before making any suggestions, especially when you are gaining experience, it is usually a good idea, if you have the time, to talk the situation over with others and research it a bit more. Instructor Notes

17 Case 2 Programming information: DDD 60–130 bpm PAV: 150 ms SAV: 120 ms
PVARP: 310 ms Student Notes Now it is your turn. Here is the strip and programming information. Analyze the strip based on this information, and think of some reasons – hypotheses – that might explain this behavior. Instructor Notes Before giving the answer – next slide - wait for the audience to figure it out and volunteer answers. Discuss the answers that seem obviously wrong based on what you know about this strip. Try to discourage guessing. If the correct answer is given first, ask if anyone has an alternative.

18 Case 2 Hypothesis Loss of Capture Click for Answer Click for Answer
Idioventricular rate is masquerading as a “capture/pseudo-fusion” Click for Answer Student Notes We see a pacing spike here that is followed by a different morphology, and one that is not followed by any evidence of ventricular capture. Our hypothesis is: This is Loss of Capture (LOC). To test it, we could run a threshold test and check the threshold against the programmed value. What else might explain LOC other than mis-programming? Instructor Notes Before giving the answer, wait for the audience to figure it out and volunteer answers. Discuss the ones that seem obviously wrong based on what you know about this strip. Try to discourage guessing. If the correct answer is given first, ask if anyone has an alternative. Click for Answer To test hypothesis: - Perform a threshold test

19 Case 2 Considerations Causes Considerations Click for Answers
If there were changes in medications, or an MI, or the patient had renal failure, etc. ? If chronic lead impedance is high? If lead impedance is ok? If acute lead impedance is high? Considerations Program a higher output for an increased safety margin, as conditions are changing Suspect fracture. Could try unipolar temporarily, but this will likely require a lead replacement. Suspect dislodgement. Can try a higher output, but permanent fix will likely be repositioning. Likely a loose set screw. Need to re-open the pocket and retighten it. Student Notes Obviously, verifying the cause of the problem influences the considerations you would discuss. Instructor Notes Ask about each possible scenario in turn, and elicit a discussion about the answers. Click for Answers

20 Case 3 Programming information DDD 60–120 bpm PAV: 150 ms SAV: 120 ms
PVARP: 380 ms Student Notes Programmed parameters and an ECG strip on a 65-year-old male patient. Instructor Notes

21 Case 3 Hypothesis: Pacemaker Wenckebach
Upper rate behavior Is this evidence of “grouped beats?” Do we see regular atrial activity with increasing A-V intervals? Intermittent atrial undersensing Do the pauses occur because a P-wave is not sensed, and thus, not tracked? Click for Answer Student Notes What are the hypotheses? Instructor Notes Promote discussion here, give the audience time to analyze, ask questions…

22 Case 3 Hypothesis: Pacemaker Wenckebach
How do you test this hypothesis? Knowing what the patient was doing when this occurred is helpful. For example, this strip was collected while the patient was on a treadmill (exercising). Analyze the strip: The regularity of the increasing A-V intervals is obvious The regularity of the grouped beats is suggestive What other hypotheses are there? For example, intermittent atrial undersensing might look like this – test for these as well. If possible, recreate the conditions Finally, what is TARP? What are the atrial intervals? Is pacemaker Wenckebach possible? Click for Answer Student Notes When someone experienced at pacemaker follow-up sees grouped beats on an ECG, they almost always suspect pacemaker Wenckebach. A couple of keys to recognizing pacemaker Wenckebach: Obviously, the increasing A-V relationship When looking at the different groups, notice how the first A-V complexes from each group are the same, the second, the third, and so on. This pattern among the groups is suggestive. When you see sequences of tracked beats, the rate is at or near the upper tracking rate Instructor Notes

23 Case 3 Hypothesis: Pacemaker Wenckebach
Considerations Is this really a problem? The pacemaker is behaving normally What to consider if the patient’s ADL’s are compromised? Pacer Wenckebach occurs when the atrial rate increases and approaches the 2:1 block point Recall from the Timing Modules that (SAV + PVARP) = TARP, so we: Can increase the UTR And decrease TARP by: Less PVARP Less AV – use Rate Adaptive AV Use Auto-PVARP options Click for Answer Student Notes What is your suggestion? After all, this is normal and expected pacemaker behavior. If this patient is 65-years-old, otherwise healthy and reasonably active, what would be his target heart rate for exercise? A common equation for determining a patients acceptable maximum heart rate is 220 bpm minus the patient’s age. In the case of a healthy 65-year-old, about 155 bpm. The problem may not be Wenckebach, the problem may be the programmed UTR. Instructor Notes

24 Your information: Case 4 DDD 60–130 bpm PAV: 150 ms SAV: 120 ms
PVARP: 310 ms Student Notes Programmed parameters and the ECG. Instructor Notes

25 Case 4 Hypothesis What explains this atrial pace? Review question:
Intermittent atrial undersensing. The P-wave was not “seen” and the lower rate (LRL) timed out, resulting in an atrial pace Review question: Why did this atrial pace NOT capture? (Hint: Think of the ECG module.) Because the atrial pacing occurred in the absolute refractory period of the atrial muscle tissue Click for Answer Click for Answer Student Notes Why, with all this tracking, does the pacemaker need to suddenly pace? Either the P-wave immediately before the atrial pace was not sensed OR The P-wave immediately before the atrial pace fell in a refractory period If this were true, there would have to have been a ventricular sense within 310 ms BEFORE this P-wave – it had to fall in a PVARP This could occur if we had intermittent ventricular oversensing, but If there was a ventricular “oversense,” why did the device emit an atrial pace? Why did it not wait for a V-A interval to time out from this “oversensed event?” “When you hear hoof beats, don’t think of zebras.” Which of these two hypotheses is the simplest and still explains all the facts? Instructor Notes

26 Case 4 Confirming Your Hypothesis
What would you do? What would you expect to see? Interrogate and observe the rhythm P-waves without markers Click for Answers Student Notes Once Marker Channel diagnostics are added, it is easy to see this is simply a case of intermittent atrial undersensing. Instructor Notes

27 Case 4 Testing Your Hypothesis
What would you do to test your hypothesis? Perform a sensing test Is the device programmed correctly? P/R- wave amplitudes can change Check Lead Impedances Undersensing can be a symptom of a lead fracture or lead insulation failure Undersensing can be a symptom of lead dislodgement Click for Answers Student Notes Suppose Marker Channel was not available – and you will still find some pacemakers in follow-up that it isn’t available for – what do you do? Instructor Notes

28 Case 4 Considerations Suppose the device were programmed to 4.0 mV atrial sensitivity, and the P-waves measure mV. Would programming a sensing value of 2.0 mV make it more or less sensitive? Would you choose 2.0 mV or a value even more sensitive if the device operations remained normal? Why? 2.0 mV is more sensitive than 4.0 mV Program to a more sensitive value to make sure the device can sense AF, for example Click for Answers Student Notes How would you reprogram this pacemaker to make it more sensitive? In the case of P-waves at 4-5 mV, would you program a value of 2.0 mV sensitivity? Why might you want to make it more sensitive – assuming no oversensing was now evident? Instructor Notes

29 One Consequence of Atrial Undersensing
Programming information: DDD 60–120 bpm PAC: 150 ms SAV: 120 ms PVARP: 310 ms PMT (pacemaker mediated tachycardia) caused by atrial undersensing and retrograde conduction The abrupt onset is one hallmark of PMT Student Notes Let’s go off on a short tangent for a few moments. On this strip we see an abrupt onset of a tachycardia immediately following an episode of atrial undersensing. This is an example of pacemaker mediated tachycardia (PMT), also called “endless loop” tachycardia. We’ll discuss its mechanism in a minute, but when one has a dual chamber pacemaker in a mode that permits tracking (like DDD), if a loss of AV synchrony occurs, PMT is one possible outcome. Instructor Notes

30 PMT Pacemaker Mediated Tachycardia
Occurrence minimized with introduction of Auto-PVARP or dynamic TARP operations Which provide longer pacemaker atrial refractory periods at lower rates PMT is similar to a re-entrant tachycardia discussed in Module 1 Except the pacemaker forms part of the re-entrant circuit Student Notes Although the incidence of PMT was greatly reduced with the onset first of PVARP, and later with the adoption of AUTO-PVARP algorithms, we are seeing more of it as clinicians realize the benefits of longer AV delay programming in TARP-based pacemakers Instructor Notes

31 PMT Mechanism A ventricular event occurs
Paced or sensed – we show a PVC here Conducts retrograde through the AV node (typically) And results in an atrial sense Which starts an SAV, and results in a ventricular pace This is again conducted retrograde, and the sequence starts again VP, which goes retrograde V-A, resulting in an AS starting an SAV, resulting in a…VP which goes retrograde V-A resulting in an AS starting an SAV resulting in a… VP which goes retrograde V-A resulting in an AS starting an SAV resulting in a… VP which goes retrograde V-A resulting in an AS starting an SAV resulting in a… You get the idea Student Notes The mechanism of PMT is pretty straightforward, as long as you understand the mechanisms discussed in Module 1 on AV reentry. In PMT, a ventricular event conducts retrograde through the AV node, and is timed such that it is sensed on the atrial channel, and thus, tracked – resulting in a VP. This VP conducts retrograde through the AV node and is sensed on the atrial channel,… and so on. Instructor Notes

32 PMT Requirements For the sequence to be maintained:
The AV node and atrium must be able to conduct retrograde, i.e., not be depolarized The pacemaker must be able to sense this retrograde depolarization, i.e., not be in a refractory period This timing ‘ballet’ must persist Student Notes For this “endless loop” to be maintained: AV conduction must be possible The retrograde event must occur outside of a refractory period These two conditions must persist Today’s pacemakers include algorithms to reduce the likelihood of PMT, and to identify and interrupt PMT. Typically they work by manipulating PVARP. For example, “PVC Response” extends PVARP after a pacemaker-defined PVC, to reduce the likelihood of a retrograde event falling outside of a refractory period. PMT Response extends PVARP after a series of AS_VP events with certain timing relationships. Neither of these actually fixes the PMT. Instructor Notes

33 Case 5 Hypotheses Is this PMT?
Is this simply the pacemaker tracking a sinus tachycardia? DDD PAC/SAV ms, PVARP 310 ms What was the patient doing when this occurred? If exercising, it may favor tracking If at rest, be suspicious of PMT Click for Answers Student Notes Unfortunately, when you are called on to identify PMT, it is usually like this: Here is a strip of a tachycardia, AS-VP at or near the UTR. Is this PMT or simply sinus tachycardia? Could it be 2:1 atrial flutter? Instructor Notes

34 Case 5 Confirming Your Hypotheses
Click for Answers Place a magnet on the device during the tachycardia. What happens? If this is PMT, what would you expect to see? If this is tracking, what would you expect to see? A magnet makes the pacemaker DOO PMT requires atrial sensing DOO suspends the pacemaker’s sensing function, so the PMT breaks Evidence of atrial tachycardia during asynchronous operation Student Notes The simplest test to run is to place a magnet on the device. What effect will the magnet have on the ECG if it is PMT? If PMT is not present, what will the magnet show? Instructor Notes Ask these questions (above) and reveal the answers.

35 Case 5 Confirming Your Hypotheses
Place a magnet on the device DOO suspends sensing and the tachycardia terminates No evidence of atrial tachycardia during the asynchronous operation Student Notes On this slide we see that PMT is confirmed – why? If PMT was not present, what would you expect to see? Instructor Notes

36 Case 5 Considerations The AV node and atrium must be able to conduct retrograde (i.e., not be depolarized) The pacemaker must be able to sense this retrograde depolarization (i.e., atrial event falling outside of a refractory period) Typical causes Loss of atrial capture Loss of atrial sensing (atrial undersensing) Atrial oversensing PVC with retrograde conduction/accessory pathway PVARP too short Auto-PVARP not in use PVC Response not in use Student Notes Diagnosing a PMT and fixing it are two different things. Although PMT is annoying to patients, and sometimes presents a challenge to diagnose, it is usually not difficult to fix – it only demands you uncover the cause. Rarely is an accessory pathway involved that might require an ablation and/or medications. Typically it results from a sensing or capture problem. Instructor Notes

37 Addressing PMT Test To fix Atrial output threshold Atrial sensing test
Retrograde conduction To fix Reprogram the pacemaker outputs as needed Increase PVARP to make the retrograde atrial event an AR Turn PMT Intervention “On” Turn PVC Response “On” Rarely, may need to reposition a lead or ablate a pathway Student Notes Thus, performing atrial output threshold and sensing threshold tests are in order. To perform a retrograde conduction test: Go to temporary tests Program to VDI and pace at different rates Observe the ECG for retrograde conduction (atrial events falling consistently at the same interval after the ventricular pace) If the results of these tests seem normal, it might be a good idea to double check your diagnosis of PMT by running a retrograde conduction test. The basic instructions are listed – but here is why: Retrograde conduction, while normal, is not present in everyone. If the patient cannot conduct retrograde, then it is unlikely the event is PMT. Instructor Notes

38 Solution: PVC Response
Designed to prevent sensing of retrograde P-waves, when they happen due to a PVC Student Notes One way to prevent sensing retrograde P-waves, when they happen due to a PVC, is "PVC Response." Medtronic pacemakers define a PVC as the second of any two consecutive ventricular events, with no intervening atrial event. When PVC Response is programmed On, a pacemaker-defined PVC starts an extended PVARP of 400 msec, if the programmed PVARP is less than 400 msec. This extended PVARP allows retrograde P-waves, should they occur, to fall within the refractory period and, therefore, does not initiate an SAV. In Medtronic pacemakers, PVC Response is programmable and is nominally programmed On. Instructor Notes

39 Solution: PMT Intervention
Designed to interrupt a Pacemaker-Mediated Tachycardia Student Notes If a PMT is initiated, PMT Intervention may be able to stop the PMT cycle. If PMT Intervention is programmed On, the pacemaker will monitor for a PMT by looking for eight consecutive VA Intervals that meet all of the following conditions: Duration less than 400 msec Start with a ventricular paced event End with an atrial sensed event If PMT Intervention is ON, and the above conditions are met, the PVARP will be forced to 400 msec after the ninth paced ventricular event. By extending the PVARP, the intent is to interrupt atrial tracking for one cycle and break the PMT. After an intervention, PMT Intervention is automatically suspended for 90 seconds before the pacemaker can monitor for a PMT again. Instructor Notes DDD / 60 / 120

40 Case 6 Programming information Any hypotheses? Click for Hint
DDD 60–130 bpm PAV: 150 ms SAV: 120 ms PVARP: 320 ms Any hypotheses? Atrial undersensing Ventricular oversensing Click for Hint Student Notes Ok, we are done with our tangent and back to more typical troubleshooting. Here is the strip and basic parameters. What hypotheses can you form? Instructor Notes

41 Case 6 Hypothesis: Atrial Undersensing
If this P-wave is not sensed, and not tracked, then determine when the next atrial event should occur in the timing sequence DDD 60 (1000 ms) minus the SAV (120 ms) = 880 ms from the last QRS to the next atrial pace (the V-A interval). We should see an atrial pace at the X. Thus, this cannot be atrial undersensing X Student Notes One hypothesis is atrial undersensing – let’s examine this for a minute as it illustrates a point raised in an earlier strip Case 4. If we assume the P-wave (in red circle) is not sensed, and this is why it isn’t tracked, we have to then figure out when the lower rate interval will time out and deliver the escape pace. We know the LR is 1000 ms and the SAV = 120 ms, so the next AP should have occurred 880 ms from the VP (the X). But there is no atrial pace at this point – so is atrial undersensing the problem? No. Instructor Notes Ask: Is there any other evidence that this is not atrial undersensing? Yes, the first P-wave may appear to be tracked, but the AV delay is too long. The sensed AV delay is only 120 ms.

42 Case 6 Hypothesis: Ventricular Oversensing
Remember the information A-A = 1000 ms A-V = 120 ms PVARP 320 ms Calculated the V-A = 880 ms AR VS Student Notes What could be another reason the P-wave is not tracked? Suppose this falls in a refractory period? It is then ignored by the pacemaker and not used for timing. Move ahead to the next “normal” complex and measure the V-A interval back towards the previous complex, starting at the atrial pace. Assume for our new hypothesis that at this interval, the pacemaker sensed a ventricular event. If we then measure the PVARP, we see that the P-wave falls in the PVARP of this “event.” So does intermittent ventricular oversensing explain this strip? Instructor Notes Measure the V-A interval from the atrial pace, and assume the pacemaker sensed a ventricular “event” here. The atrial event then fell in the PVARP of this “event” – and can not be used for timing, thus it did not start an SAV.

43 Case 6 Confirming the Hypothesis: Ventricular Oversensing
Click for Answers What would you do? What would you expect to see? Interrogate and observe the rhythm VS/VR markers without QRS complexes Student Notes When you see the Marker Channel diagnostics it becomes clear. The pacemaker is sensing a lot of activity on the ventricular channel. These might be myopotentials, or as a result of an insulation failure on the lead. Instructor Notes

44 Case 6 Confirming the Hypothesis: Ventricular Oversensing
But suppose you interrogate and consistently get this strip. What next? Click for Answers Run a sensing test anyway Try to provoke oversensing Program to non-RR mode Arm/shoulder movement Have patient reach across his/her body Observe Marker Channel for VS without a QRS More common with unipolar sensing Student Notes Suppose that when you interrogate the device and have Marker Channel diagnostics available, the oversensing is not apparent? Although not common, this is not unheard of either. What can you do to try to confirm your hypothesis so you can make a suggestion, if asked? Certainly check the lead impedance. Try to provoke an episode with the patient monitored and the follow-up staff prepared. Instructor Notes

45 Review Questions Click for Answers What patient complaints might you suspect with this strip? What pacemaker telemetry data might indicate the cause? What long-term effect will this condition have on device diagnostics? C/O syncope, presyncope, vertigo, weakness… Ventricular lead impedance Ventricular rate diagnostics inaccurate because of this oversensing – may be interpreted as arrhythmia Student Notes Instructor Notes

46 A Little Advice… When you see evidence of “over pacing” i.e., pacing despite intrinsic activity Consider undersensing See Case 4 When you see evidence of “under-pacing” i.e., pauses without pacing Consider oversensing See Case 6 These rules are NOT absolute Student Notes Instructor Notes

47 Case 7 No Programmer Available
Questions to ask yourself: Is this a single chamber VVI pacemaker? If it is dual chamber, is it tracking? But if it is tracking what would cause AV intervals to change? If it is not tracking, e.g., because of atrial undersensing, what causes the V pacing? Can’t be VVI, see A-V pacing. Must be dual-chamber device Click for Hints Click for Answers Hard to believe this is tracking with these AV intervals, and it can’t be Wenckebach at this rate Good question! Student Notes Instructor Notes

48 Case 7 No Programmer Available
Click for Answers Questions to ask yourself: What kind of pacemaker: Paces in the atrium and ventricle Senses in the atrium and ventricle But does NOT track? The simplest answer that explains all the facts, is likely the correct answer. How about DDI(R) The response to sensing is to inhibit No SAV can be initiated Without an AP, the ventricle is paced at the lower rate If after a V-A interval, there is no AS, then an AP and a PAV Click for Hints Student Notes So what kind of a pacemaker behaves this way? Instructor Notes

49 Case 7 Review Questions Click for Answers
What is the underlying rhythm? Is the pacing mode appropriate for this rhythm? What would be a better choice? Why? It appears to be Complete Heart Block No evidence of AV synchrony DDIR? No DDD or even VDD It looks like the atrium is reliable Student Notes Now the physician asks: “Is this an appropriate pacemaker for the patient? What would you suggest and why?” Instructor Notes

50 Case 8 No Programmer Available
Patient is in the hospital on bed rest Admitted for non-cardiac problem Medical record indicates he has a dual chamber pacemaker Student Notes Instructor Notes A physician hands you this and says, ”I think he is having PMT, what is your opinion?”

51 Case 8 No Programmer Available: Hypotheses
Is this PMT? If not PMT, what would cause atrial pacing at this rate (which is…?) How can it be Rate Response – he is at rest? No, PMT requires tracking – this shows atrial pacing Atrial rate of about 100 bpm Could be Rate Reponse pacing Or a special pacemaker intervention Rate Response could be programmed too aggressively. It might be an MV sensor, and he is having a fever or an anxiety attack… Click for Answers Student Notes How can it be a PMT? PMT requires tracking and, in this case, we see atrial pacing. But now – why is the pacemaker pacing this fast for a patient on bed rest? At this point we can only guess, as we need a programmer to confirm the parameters. However, if the programmer is truly not available, where else could you go to find out what might be going on? Instructor Notes

52 Case 8 No Programmer Available: Confirming the Hypothesis
What resources are available to you? Medical Record and Nurse Office pacemaker chart Technical Services Patient What information would you look for? Mode of pacemaker Patient vital signs/activity Model Last programmed values Indication Interpretation/Confirmation of the ECG strip Other explanations What were you doing? Student Notes Instructor Notes Click for Answers

53 Case 9 Programming information
DDDR bpm PAV: 150 ms SAV 120 ms PVARP: Auto No other therapies or unusual programming options chosen How can there be pacing and sensing at less than the lower rate? Is this pacemaker malfunctioning? Atrial Rate Histogram Student Notes Here is a tricky case and also one that is very common. The question by the clinician usually goes something like this: “I put in this device and programmed it to a lower rate of 60. Now I see it is pacing at a rate of 40 or less. Something is wrong.” Instructor Notes

54 Case 9 Hypotheses Phenomena: Hypotheses:
The device pace appears to be operating at less than the lower rate Hypotheses: There are special programming options that could affect the histogram producing these results Hysteresis Sleep Function The device is actually programmed to a lower rate of 40 bpm The programming information is correct, so the device is malfunctioning Student Notes Well, what could be the problem? Instructor Notes

55 Case 9 Why is the Pacemaker Altering the Lower Rate?
Interrogation confirms: Programming information is correct DDDR bpm, PAV/SAV 150/120 ms, PVARP-Auto Hysteresis and Sleep Function: Off Click for Hint Recall from Module 7: Normally, pacemakers use A-A timing to maintain a steady atrial rate. V-V timing is used only under some special circumstances. This is an example of the effect the change in fundamental timing has on the pacemaker. Student Notes When you interrogate, you find that the mode and programming information you were given is correct and no special operations are in effect. This is an example of something discussed earlier – what happens when a device changes from A-A timing to V-V timing? Instructor Notes

56 Case 9 Basic IPG timing is A-A, but after a (pacemaker-defined) PVC, it switches to V-V timing This maintains a stable V-V interval (at the lower or sensor indicated rate, whichever is faster and depending on the mode) The resulting AS-AP interval may exceed LRL and is noted in the histogram DDDR 60/130 1600ms Student Notes The pacemaker is designed to try to provide a stable ventricular rate. So in the presence of a PVC, the pacemaker is designed, in effect, to provide a compensatory pause. However, this pause, which occurs as a result of A-A timing, then V-V timing, can also result in a prolonged V-A interval. This interval is noted in the histograms. Thus, this is really a normal (but confusing) operation. Instructor Notes

57 Case 9 Considerations Is the pacemaker malfunctioning?
Is the patient symptomatic with this pacemaker operation? What do you suggest? No, this is normal pacemaker behavior Unlikely, as the ventricular rate is relatively stable The pacemaker is implanted in order to address patient symptoms. Concentrate on the patient, not on the diagnostic. Student Notes This is really a case of not fixing it because it isn’t broken. But rest assured, this question comes up quite often. Instructor Notes Click for Answers

58 Recap The Four Solutions to Pacemaker Problems
Re-Program – the device Re-Place – the system or a component Re-Position – the lead(s), the device Retreat – do nothing, because nothing is wrong So…. Observe/Collect data Measure (e.g., A-A, V-V, A-V, V-A) Form your hypothesis Test your “solution” Make a suggestion Student Notes A recap… Instructor Notes

59 Final Nugget Most pacemaker “malfunctions” can be explained by:
Dislodged leads or failing leads Battery end-of-life Inappropriate programming due to Changing patient conditions An error Normal operations you do not fully understand Sudden changes in timing are almost always normal pacemaker (if advanced) operations Student Notes …and a last bit of advice. Instructor Notes

60 Brief Statements Indications
Implantable Pulse Generators (IPGs) are indicated for rate adaptive pacing in patients who ay benefit from increased pacing rates concurrent with increases in activity and increases in activity and/or minute ventilation. Pacemakers are also indicated for dual chamber and atrial tracking modes in patients who may benefit from maintenance of AV synchrony. Dual chamber modes are specifically indicated for treatment of conduction disorders that require restoration of both rate and AV synchrony, which include various degrees of AV block to maintain the atrial contribution to cardiac output and VVI intolerance (e.g. pacemaker syndrome) in the presence of persistent sinus rhythm. Implantable cardioverter defibrillators (ICDs) are indicated for ventricular antitachycardia pacing and ventricular defibrillation for automated treatment of life-threatening ventricular arrhythmias. Cardiac Resynchronization Therapy (CRT) ICDs are indicated for ventricular antitachycardia pacing and ventricular defibrillation for automated treatment of life-threatening ventricular arrhythmias and for the reduction of the symptoms of moderate to severe heart failure (NYHA Functional Class III or IV) in those patients who remain symptomatic despite stable, optimal medical therapy and have a left ventricular ejection fraction less than or equal to 35% and a QRS duration of ≥130 ms. CRT IPGs are indicated for the reduction of the symptoms of moderate to severe heart failure (NYHA Functional Class III or IV) in those patients who remain symptomatic despite stable, optimal medical therapy, and have a left ventricular ejection fraction less than or equal to 35% and a QRS duration of ≥130 ms. Contraindications IPGs and CRT IPGs are contraindicated for dual chamber atrial pacing in patients with chronic refractory atrial tachyarrhythmias; asynchronous pacing in the presence (or likelihood) of competitive paced and intrinsic rhythms; unipolar pacing for patients with an implanted cardioverter defibrillator because it may cause unwanted delivery or inhibition of ICD therapy; and certain IPGs are contraindicated for use with epicardial leads and with abdominal implantation. ICDs and CRT ICDs are contraindicated in patients whose ventricular tachyarrhythmias may have transient or reversible causes, patients with incessant VT or VF, and for patients who have a unipolar pacemaker. ICDs are also contraindicated for patients whose primary disorder is bradyarrhythmia.

61 Brief Statements (continued)
Warnings/Precautions Changes in a patient’s disease and/or medications may alter the efficacy of the device’s programmed parameters. Patients should avoid sources of magnetic and electromagnetic radiation to avoid possible underdetection, inappropriate sensing and/or therapy delivery, tissue damage, induction of an arrhythmia, device electrical reset or device damage. Do not place transthoracic defibrillation paddles directly over the device. Additionally, for CRT ICDs and CRT IPGs, certain programming and device operations may not provide cardiac resynchronization. Also for CRT IPGs, Elective Replacement Indicator (ERI) results in the device switching to VVI pacing at 65 ppm. In this mode, patients may experience loss of cardiac resynchronization therapy and / or loss of AV synchrony. For this reason, the device should be replaced prior to ERI being set. Potential complications Potential complications include, but are not limited to, rejection phenomena, erosion through the skin, muscle or nerve stimulation, oversensing, failure to detect and/or terminate arrhythmia episodes, and surgical complications such as hematoma, infection, inflammation, and thrombosis. An additional complication for ICDs and CRT ICDs is the acceleration of ventricular tachycardia. See the device manual for detailed information regarding the implant procedure, indications, contraindications, warnings, precautions, and potential complications/adverse events. For further information, please call Medtronic at and/or consult Medtronic’s website at Caution: Federal law (USA) restricts these devices to sale by or on the order of a physician.

62 Brief Statement: Medtronic Leads
Indications Medtronic leads are used as part of a cardiac rhythm disease management system. Leads are intended for pacing and sensing and/or defibrillation. Defibrillation leads have application for patients for whom implantable cardioverter defibrillation is indicated Contraindications Medtronic leads are contraindicated for the following: ventricular use in patients with tricuspid valvular disease or a tricuspid mechanical heart valve. patients for whom a single dose of 1.0 mg of dexamethasone sodium phosphate or dexamethasone acetate may be contraindicated. (includes all leads which contain these steroids) Epicardial leads should not be used on patients with a heavily infracted or fibrotic myocardium. The SelectSecure Model 3830 Lead is also contraindicated for the following: patients for whom a single dose of 40.µg of beclomethasone dipropionate may be contraindicated. patients with obstructed or inadequate vasculature for intravenous catheterization.

63 Brief Statement: Medtronic Leads (continued)
Warnings/Precautions People with metal implants such as pacemakers, implantable cardioverter defibrillators (ICDs), and accompanying leads should not receive diathermy treatment. The interaction between the implant and diathermy can cause tissue damage, fibrillation, or damage to the device components, which could result in serious injury, loss of therapy, or the need to reprogram or replace the device. For the SelectSecure Model 3830 lead, total patient exposure to beclomethasone 17,21-dipropionate should be considered when implanting multiple leads. No drug interactions with inhaled beclomethasone 17,21-dipropionate have been described. Drug interactions of beclomethasone 17,21-dipropionate with the Model 3830 lead have not been studied. Potential Complications Potential complications include, but are not limited to, valve damage, fibrillation and other arrhythmias, thrombosis, thrombotic and air embolism, cardiac perforation, heart wall rupture, cardiac tamponade, muscle or nerve stimulation, pericardial rub, infection, myocardial irritability, and pneumothorax. Other potential complications related to the lead may include lead dislodgement, lead conductor fracture, insulation failure, threshold elevation or exit block. See specific device manual for detailed information regarding the implant procedure, indications, contraindications, warnings, precautions, and potential complications/adverse events. For further information, please call Medtronic at and/or consult Medtronic’s website at Caution: Federal law (USA) restricts this device to sale by or on the order of a physician.

64 Disclosure NOTE: This presentation is provided for general educational purposes only and should not be considered the exclusive source for this type of information. At all times, it is the professional responsibility of the practitioner to exercise independent clinical judgment in a particular situation. Student Notes Instructor Notes

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