Presentation on theme: "Pacemaker Troubleshooting Module 9"— Presentation transcript:
1Pacemaker Troubleshooting Module 9 Student NotesIn 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 NotesThis module should take approximately 2 hours to cover.To deliver this module the following materials are suggested:Printed Participant Guides for each participantOverhead projector and screenOptional: Whiteboard or flip chartWhile 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 HeadquartersMedtronic, Inc.710 Medtronic ParkwayMinneapolis, MNUSAInternet:Tel: (763)EuropeMedtronic International Trading SàrlRoute du MolliauCh TolochenazSwitzerlandTel: (41 21)Asia-PacificMedtronic International, Ltd.16/F Manulife PlazaThe Lee Gardens, 33 Hysan AvenueCauseway BayHong KongTel: (852)CanadaMedtronic of Canada Ltd.6733 Kitimat RoadMississauga, Ontario L5N 1W3Tel: (905)Toll-free: 1 (800)Medtronic USA, Inc.Toll-free: 1 (800)(24-hour technical support for physicians and medical professionals)Latin AmericaMedtronic USA, Inc.Doral Corporate Center II3750 NW 87th Avenue Suite 700Miami, FL 33178USATel: (305)UC d ENMedtronic, Inc.Minneapolis, MNFebruary 2008
2Objectives List steps in performing troubleshooting Correctly identify the following on an ECG strip:Pacemaker ERI behaviorLoss of CaptureOver- and undersensingMagnet behaviorPseudo-malfunctionsMake clinically appropriate suggestions based on interpretationIdentify additional information or other resources useful to diagnosing pacemaker malfunctionStudent NotesThe objectives are listed here.Instructor Notes
3Some Good AdvicePerform all troubleshooting and all pacemaker checks the same wayCollect the dataAsk questionsKeep an open mindAnalyze, form hypothesis, testDon’t make assumptionsThe simplest explanation that covers all the facts, is usually the correct explanationStudent NotesPacemaker 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 NotesUse 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.
4The Four Solutions to Pacemaker Problems Re-Program – the deviceRe-Place – the system or a componentRe-Position – the lead(s), the deviceRetreat – do nothing, because nothing is wrongStudent NotesFundamentally 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 NotesThe four basic solutions to pacemaker malfunction.
5The Process Observe/collect data Form your hypothesis Measure the ECG (e.g., A-A, V-V, A-V, V-A)Form your hypothesisTest your “solution”Make a suggestionAsk the clinician questionsStudent NotesAs 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 NotesOne process, and the one that we emphasize here.
6Data Sources Programmed parameters Patient symptoms Medical history Indication for implantImplant dateRhythm stripDevice model numberLead model numbersTelemetry dataImpedancesBattery voltageMarker Channel™Device diagnosticsDevice RRT and EOS behaviorsStudent NotesThe 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 NotesData collection, especially asking the right questions, is almost an art form. Practice makes perfect.
7Case 1 Information you have: Click for Hint DDDPAV/SAV msPVARP 310 msQuestion: Why is rhythm irregular, sometimes fast?Hypotheses:Tracking PAFOversensing (tracking a “P-wave” that is not there)Are these grouped beats – upper tracking rate behavior?Click for HintStudent NotesLet’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 itAtrial oversensing and the device is ‘tracking’ itUpper rate behavior – Wenckebach – grouped beatsInstructor NotesGuide 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.
8Case 1 First Hypothesis: Tracking Paroxysmal AF What is the evidence for AF?Irregular ventricular eventsCould be “fine” AF, not visible on baselineWhat is the evidence against AF?Some visible P-wavesEvidence of atrial pacingStudent NotesOne hypothesis is that the device is tracking PAF. What evidence supports or argues against this?Evidence supporting tracking PAF:Ventricular response is irregularly irregularVariable P-wavesEvidence not supporting PAF tracking:Evidence of atrial pacingInstructor NotesTake the learner step-by-step through the various hypotheses to evaluate supporting and opposing evidence.This is part of the data analysis step.
9Case 1 Second Hypothesis: Atrial Oversensing What is the evidence for atrial oversensing?Irregular ventricular trackingEvidence of ventricular tracking without visible P-wavesWhat is evidence against atrial oversensing?There may be P-waves “hidden” in some T-wavesStudent NotesA 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 wellEvidence of ventricular tracking without visible P-wavesEvidence arguing against atrial oversensing:Perhaps some P-waves within T-wavesInstructor Notes
10Case 1 Third Hypothesis: Upper Rate Behavior What is the evidence for Wenckebach?Some evidence of “grouped” beatsEvidence of P-waves “hidden” in some T-wavesWhat is evidence against Wenckebach?The A-A intervals don’t march outEvidence of atrial pacing – no need if this is UTR behaviorStudent NotesA third hypothesis is upper rate behavior.Supporting this:We do see some of what appear to be grouped beatsPerhaps there are P- waves in some T-wavesArguing against this:A-A intervals do not march outWe 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 allBased on this evidence, do you agree that it is unlikely that the “problem” is merely pacemaker Wenckebach?Instructor Notes
11Case 1 What Are Your Next Steps? To form a better hypothesis:Interrogate pacemakerObserve ECG and Marker Channel stripTo test the hypothesis:Perform sensing test – observe rhythm/markersCheck lead impedance for low impedance (insulation break), which often causes oversensing (< about 250 Ω)What is the normal impedance range (assume standard leads)?Student NotesSo this situation is either:True AF with tracking, orAtrial oversensing with inappropriate trackingHow 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 NotesNow we will test the two likely hypotheses.
12Case 1 Final Hypothesis: Arial Oversensing Confirmed byMarker Channel annotations showing AS markers without P-wavesStudent NotesMarker Channel annotations confirm atrial oversensing. Obviously, this is a tool that can make you look very smart.Instructor NotesThis is our conclusion: Atrial oversensing.
13Case 1 Conclusion: Arial Oversensing What do you consider?The “service” you provide to the customer is not in just interpreting pacemaker behaviorYou are there to supplement the customer’s clinical knowledge and experience with your knowledge and experience regarding the pacing systemIf the customer asks, you have to be ready to make an appropriate suggestionAsk questionsFind out the relevant concerns that the customer has for this patientIf you are uncertain, call Technical ServicesStudent NotesOK, 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 NotesHowever, we are not necessarily finished.
14Example Case 1 Conclusion: Arial Oversensing CauseInsulation breachBipolar impedance: 190 ΩStudent NotesLet’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
15Example Case 1 Conclusion: Artial Oversensing Considerations:How easy is it to “fix”Unipolar lead in situWhat are the risks to the patient to “fix”Elderly, debilitated patientWhat are the risks/implications if it is not “fixed”Loss of AV synchronyPossible that AF diagnostics are not accurateRisk of PMTAre there any alternatives?VVI?Student NotesSuppose it is more complicated. Let’s say the lead is already unipolar. Your choice then is:To accept the oversensingTo replace the leadTo reprogram the pacemaker to VVIAgain, 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 VVIUltimately, 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
16Example Case 1 Conclusion: Arial Oversensing CauseUnknownOther resourcesMedtronic Technical Services(within the U.S.)Medtronic Product Performance ReportThere may be an issue with a particular Medtronic product you are not aware ofOther manufacturers do not necessarily produce these reportsYour colleaguesStudent NotesFinally, 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
17Case 2 Programming information: DDD 60–130 bpm PAV: 150 ms SAV: 120 ms PVARP: 310 msStudent NotesNow 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 NotesBefore 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.
18Case 2 Hypothesis Loss of Capture Click for Answer Click for Answer Idioventricular rate is masquerading as a “capture/pseudo-fusion”Click for AnswerStudent NotesWe 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 NotesBefore 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 AnswerTo test hypothesis:- Perform a threshold test
19Case 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?ConsiderationsProgram a higher output for an increased safety margin, as conditions are changingSuspect 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 NotesObviously, verifying the cause of the problem influences the considerations you would discuss.Instructor NotesAsk about each possible scenario in turn, and elicit a discussion about the answers.Click for Answers
20Case 3 Programming information DDD 60–120 bpm PAV: 150 ms SAV: 120 ms PVARP: 380 msStudent NotesProgrammed parameters and an ECG strip on a 65-year-old male patient.Instructor Notes
21Case 3 Hypothesis: Pacemaker Wenckebach Upper rate behaviorIs this evidence of “grouped beats?”Do we see regular atrial activity with increasing A-V intervals?Intermittent atrial undersensingDo the pauses occur because a P-wave is not sensed, and thus, not tracked?Click for AnswerStudent NotesWhat are the hypotheses?Instructor NotesPromote discussion here, give the audience time to analyze, ask questions…
22Case 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 obviousThe regularity of the grouped beats is suggestiveWhat other hypotheses are there? For example, intermittent atrial undersensing might look like this – test for these as well.If possible, recreate the conditionsFinally, what is TARP? What are the atrial intervals? Is pacemaker Wenckebach possible?Click for AnswerStudent NotesWhen 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 relationshipWhen 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 rateInstructor Notes
23Case 3 Hypothesis: Pacemaker Wenckebach ConsiderationsIs this really a problem?The pacemaker is behaving normallyWhat to consider if the patient’s ADL’s are compromised?Pacer Wenckebach occurs when the atrial rate increases and approaches the 2:1 block pointRecall from the Timing Modules that (SAV + PVARP) = TARP, so we:Can increase the UTRAnd decrease TARP by:Less PVARPLess AV – use Rate Adaptive AVUse Auto-PVARP optionsClick for AnswerStudent NotesWhat 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
24Your information: Case 4 DDD 60–130 bpm PAV: 150 ms SAV: 120 ms PVARP: 310 msStudent NotesProgrammed parameters and the ECG.Instructor Notes
25Case 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 paceReview 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 tissueClick for AnswerClick for AnswerStudent NotesWhy, with all this tracking, does the pacemaker need to suddenly pace?Either the P-wave immediately before the atrial pace was not sensedORThe P-wave immediately before the atrial pace fell in a refractory periodIf 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 PVARPThis could occur if we had intermittent ventricular oversensing, butIf 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
26Case 4 Confirming Your Hypothesis What would you do?What would you expect to see?Interrogate and observe the rhythmP-waves without markersClick for AnswersStudent NotesOnce Marker Channel diagnostics are added, it is easy to see this is simply a case of intermittent atrial undersensing.Instructor Notes
27Case 4 Testing Your Hypothesis What would you do to test your hypothesis?Perform a sensing testIs the device programmed correctly?P/R- wave amplitudes can changeCheck Lead ImpedancesUndersensing can be a symptom of a lead fracture or lead insulation failureUndersensing can be a symptom of lead dislodgementClick for AnswersStudent NotesSuppose 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
28Case 4 ConsiderationsSuppose 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 mVProgram to a more sensitive value to make sure the device can sense AF, for exampleClick for AnswersStudent NotesHow 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
29One Consequence of Atrial Undersensing Programming information:DDD 60–120 bpmPAC: 150 msSAV: 120 msPVARP: 310 msPMT (pacemaker mediated tachycardia) caused by atrial undersensing and retrograde conductionThe abrupt onset is one hallmark of PMTStudent NotesLet’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
30PMT Pacemaker Mediated Tachycardia Occurrence minimized with introduction of Auto-PVARP or dynamic TARP operationsWhich provide longer pacemaker atrial refractory periods at lower ratesPMT is similar to a re-entrant tachycardia discussed in Module 1Except the pacemaker forms part of the re-entrant circuitStudent NotesAlthough 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 pacemakersInstructor Notes
31PMT Mechanism A ventricular event occurs Paced or sensed – we show a PVC hereConducts retrograde through the AV node (typically)And results in an atrial senseWhich starts an SAV, and results in a ventricular paceThis is again conducted retrograde, and the sequence starts againVP, 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 ideaStudent NotesThe 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
32PMT Requirements For the sequence to be maintained: The AV node and atrium must be able to conduct retrograde, i.e., not be depolarizedThe pacemaker must be able to sense this retrograde depolarization, i.e., not be in a refractory periodThis timing ‘ballet’ must persistStudent NotesFor this “endless loop” to be maintained:AV conduction must be possibleThe retrograde event must occur outside of a refractory periodThese two conditions must persistToday’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
33Case 5 Hypotheses Is this PMT? Is this simply the pacemaker tracking a sinus tachycardia?DDD PAC/SAV ms, PVARP 310 msWhat was the patient doing when this occurred?If exercising, it may favor trackingIf at rest, be suspicious of PMTClick for AnswersStudent NotesUnfortunately, 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
34Case 5 Confirming Your Hypotheses Click for AnswersPlace 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 DOOPMT requires atrial sensingDOO suspends the pacemaker’s sensing function, so the PMT breaksEvidence of atrial tachycardia during asynchronous operationStudent NotesThe 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 NotesAsk these questions (above) and reveal the answers.
35Case 5 Confirming Your Hypotheses Place a magnet on the deviceDOO suspends sensing and the tachycardia terminatesNo evidence of atrial tachycardia during the asynchronous operationStudent NotesOn this slide we see that PMT is confirmed – why? If PMT was not present, what would you expect to see?Instructor Notes
36Case 5 ConsiderationsThe 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 causesLoss of atrial captureLoss of atrial sensing (atrial undersensing)Atrial oversensingPVC with retrograde conduction/accessory pathwayPVARP too shortAuto-PVARP not in usePVC Response not in useStudent NotesDiagnosing 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
37Addressing PMT Test To fix Atrial output threshold Atrial sensing test Retrograde conductionTo fixReprogram the pacemaker outputs as neededIncrease PVARP to make the retrograde atrial event an ARTurn PMT Intervention “On”Turn PVC Response “On”Rarely, may need to reposition a lead or ablate a pathwayStudent NotesThus, performing atrial output threshold and sensing threshold tests are in order.To perform a retrograde conduction test:Go to temporary testsProgram to VDI and pace at different ratesObserve 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
38Solution: PVC Response Designed to prevent sensing of retrograde P-waves, when they happen due to a PVCStudent NotesOne 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
39Solution: PMT Intervention Designed to interrupt a Pacemaker-Mediated TachycardiaStudent NotesIf 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 msecStart with a ventricular paced eventEnd with an atrial sensed eventIf 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 NotesDDD / 60 / 120
40Case 6 Programming information Any hypotheses? Click for Hint DDD 60–130 bpmPAV: 150 msSAV: 120 msPVARP: 320 msAny hypotheses?Atrial undersensingVentricular oversensingClick for HintStudent NotesOk, 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
41Case 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 sequenceDDD 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 undersensingXStudent NotesOne 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 NotesAsk: 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.
42Case 6 Hypothesis: Ventricular Oversensing Remember the informationA-A = 1000 msA-V = 120 msPVARP 320 msCalculated the V-A = 880 msARVSStudent NotesWhat 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 NotesMeasure 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.
43Case 6 Confirming the Hypothesis: Ventricular Oversensing Click for AnswersWhat would you do?What would you expect to see?Interrogate and observe the rhythmVS/VR markers without QRS complexesStudent NotesWhen 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
44Case 6 Confirming the Hypothesis: Ventricular Oversensing But suppose you interrogate and consistently get this strip. What next?Click for AnswersRun a sensing test anywayTry to provoke oversensingProgram to non-RR modeArm/shoulder movementHave patient reach across his/her bodyObserve Marker Channel for VS without a QRSMore common with unipolar sensingStudent NotesSuppose 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
45Review QuestionsClick for AnswersWhat 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 impedanceVentricular rate diagnostics inaccurate because of this oversensing – may be interpreted as arrhythmiaStudent NotesInstructor Notes
46A Little Advice…When you see evidence of “over pacing” i.e., pacing despite intrinsic activityConsider undersensingSee Case 4When you see evidence of “under-pacing” i.e., pauses without pacingConsider oversensingSee Case 6These rules are NOT absoluteStudent NotesInstructor Notes
47Case 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 deviceClick for HintsClick for AnswersHard to believe this is tracking with these AV intervals, and it can’t be Wenckebach at this rateGood question!Student NotesInstructor Notes
48Case 7 No Programmer Available Click for AnswersQuestions to ask yourself:What kind of pacemaker:Paces in the atrium and ventricleSenses in the atrium and ventricleBut 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 inhibitNo SAV can be initiatedWithout an AP, the ventricle is paced at the lower rateIf after a V-A interval, there is no AS, then an AP and a PAVClick for HintsStudent NotesSo what kind of a pacemaker behaves this way?Instructor Notes
49Case 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 BlockNo evidence of AV synchronyDDIR? NoDDD or even VDDIt looks like the atrium is reliableStudent NotesNow the physician asks: “Is this an appropriate pacemaker for the patient? What would you suggest and why?”Instructor Notes
50Case 8 No Programmer Available Patient is in the hospital on bed restAdmitted for non-cardiac problemMedical record indicates he has a dual chamber pacemakerStudent NotesInstructor NotesA physician hands you this and says, ”I think he is having PMT, what is your opinion?”
51Case 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 pacingAtrial rate of about 100 bpmCould be Rate Reponse pacingOr a special pacemaker interventionRate Response could be programmed too aggressively. It might be an MV sensor, and he is having a fever or an anxiety attack…Click for AnswersStudent NotesHow 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
52Case 8 No Programmer Available: Confirming the Hypothesis What resources are available to you?Medical Record and NurseOffice pacemaker chartTechnical ServicesPatientWhat information would you look for?Mode of pacemakerPatient vital signs/activityModelLast programmed valuesIndicationInterpretation/Confirmation of the ECG stripOther explanationsWhat were you doing?Student NotesInstructor NotesClick for Answers
53Case 9 Programming information DDDR bpmPAV: 150 msSAV 120 msPVARP: AutoNo other therapies or unusual programming options chosenHow can there be pacing and sensing at less than the lower rate?Is this pacemaker malfunctioning?Atrial Rate HistogramStudent NotesHere 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
54Case 9 Hypotheses Phenomena: Hypotheses: The device pace appears to be operating at less than the lower rateHypotheses:There are special programming options that could affect the histogram producing these resultsHysteresisSleep FunctionThe device is actually programmed to a lower rate of 40 bpmThe programming information is correct, so the device is malfunctioningStudent NotesWell, what could be the problem?Instructor Notes
55Case 9 Why is the Pacemaker Altering the Lower Rate? Interrogation confirms:Programming information is correctDDDR bpm, PAV/SAV 150/120 ms, PVARP-AutoHysteresis and Sleep Function: OffClick for HintRecall 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 NotesWhen 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
56Case 9Basic IPG timing is A-A, but after a (pacemaker-defined) PVC, it switches to V-V timingThis 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 histogramDDDR 60/1301600msStudent NotesThe 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
57Case 9 Considerations Is the pacemaker malfunctioning? Is the patient symptomatic with this pacemaker operation?What do you suggest?No, this is normal pacemaker behaviorUnlikely, as the ventricular rate is relatively stableThe pacemaker is implanted in order to address patient symptoms. Concentrate on the patient, not on the diagnostic.Student NotesThis is really a case of not fixing it because it isn’t broken. But rest assured, this question comes up quite often.Instructor NotesClick for Answers
58Recap The Four Solutions to Pacemaker Problems Re-Program – the deviceRe-Place – the system or a componentRe-Position – the lead(s), the deviceRetreat – do nothing, because nothing is wrongSo….Observe/Collect dataMeasure (e.g., A-A, V-V, A-V, V-A)Form your hypothesisTest your “solution”Make a suggestionStudent NotesA recap…Instructor Notes
59Final Nugget Most pacemaker “malfunctions” can be explained by: Dislodged leads or failing leadsBattery end-of-lifeInappropriate programming due toChanging patient conditionsAn errorNormal operations you do not fully understandSudden changes in timing are almost always normal pacemaker (if advanced) operationsStudent Notes…and a last bit of advice.Instructor Notes
60Brief 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.ContraindicationsIPGs 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.
61Brief Statements (continued) Warnings/PrecautionsChanges 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 complicationsPotential 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 atCaution: Federal law (USA) restricts these devices to sale by or on the order of a physician.
62Brief Statement: Medtronic Leads IndicationsMedtronic 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 indicatedContraindicationsMedtronic 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.
63Brief Statement: Medtronic Leads (continued) Warnings/PrecautionsPeople 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 ComplicationsPotential 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 atCaution: Federal law (USA) restricts this device to sale by or on the order of a physician.
64DisclosureNOTE: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 NotesInstructor Notes