Pacemaker Troubleshooting Module 9

1. Pacemaker TroubleshootingModule 9

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

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

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

5. The Process • Observe/collect data • 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

6. 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 Data Sources

7. Case 1 • Information you have: • DDD 60-130 • PAV/SAV 150-120 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

8. Case 1First 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

9. Case 1Second 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

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

11. Case 1What 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)?

12. Case 1Final Hypothesis: Arial Oversensing • Confirmed by • Marker Channel annotations showing AS markers without P-waves

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

14. Example Case 1 Conclusion: Arial Oversensing • Cause • Insulation breach • Bipolar impedance: 190 Ω

15. Example Case 1Conclusion: 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?

16. Example Case 1 Conclusion: Arial Oversensing • Cause • Unknown • Other resources • Medtronic Technical Services • 1 800 505 4636 (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

17. Case 2 • Programming information: • DDD 60–130 bpm • PAV: 150 ms • SAV: 120 ms • PVARP: 310 ms

18. Case 2Hypothesis Loss of Capture • Idioventricular rate is masquerading as a “capture/pseudo-fusion” Click for Answer Click for Answer • To test hypothesis: • - Perform a threshold test

19. Causes 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. Case 2Considerations Click for Answers

20. Case 3 • Programming information • DDD 60–120 bpm • PAV: 150 ms • SAV: 120 ms • PVARP: 380 ms

21. Case 3Hypothesis: 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

22. Case 3Hypothesis: 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

23. Case 3Hypothesis: 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

24. Case 4 • Your information: • DDD 60–130 bpm • PAV: 150 ms • SAV: 120 ms • PVARP: 310 ms

25. Case 4Hypothesis • What explains this atrial pace? • 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

26. What would you do? What would you expect to see? Interrogate and observe the rhythm P-waves without markers Case 4Confirming YourHypothesis Click for Answers

27. 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 Case 4Testing Your Hypothesis Click for Answers

28. Suppose the device were programmed to 4.0 mV atrial sensitivity, and the P-waves measure 4.0- 5.0 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 Case 4Considerations Click for Answers

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

30. PMTPacemaker 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

31. 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 PMT Mechanism

32. 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 PMT Requirements

33. Case 5Hypotheses • Is this PMT? • Is this simply the pacemaker tracking a sinus tachycardia? • DDD 60-120 PAC/SAV 150-120 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

34. 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 Case 5Confirming Your Hypotheses Click for Answers

35. Case 5Confirming Your Hypotheses • Place a magnet on the device • DOO suspends sensing and the tachycardia terminates • No evidence of atrial tachycardia during the asynchronous operation

36. 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 Typical causes PVARP too short Auto-PVARP not in use PVC Response not in use Case 5Considerations

37. Addressing PMT • Test • 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

38. Solution: PVC Response • Designed to prevent sensing of retrograde P-waves, when they happen due to a PVC

39. Solution: PMT Intervention • Designed to interrupt a Pacemaker-Mediated Tachycardia DDD / 60 / 120

40. Case 6 • Programming information • DDD 60–130 bpm • PAV: 150 ms • SAV: 120 ms • PVARP: 320 ms • Any hypotheses? • Atrial undersensing • Ventricular oversensing Click for Hint

41. X Case 6Hypothesis: 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

42. PVARP 320 ms Calculated the V-A = 880 ms AR VS Case 6Hypothesis: Ventricular Oversensing • Remember the information • A-A = 1000 ms • A-V = 120 ms 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 6Confirming 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

44. 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 Case 6Confirming the Hypothesis: Ventricular Oversensing • But suppose you interrogate and consistently get this strip. What next? Click for Answers

45. C/O syncope, presyncope, vertigo, weakness… Ventricular lead impedance Ventricular rate diagnostics inaccurate because of this oversensing – may be interpreted as arrhythmia 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?

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

47. Hard to believe this is tracking with these AV intervals, and it can’t be Wenckebach at this rate Good question! Case 7No 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

48. 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 Case 7No Programmer Available Click for Answers Click for Hints

49. 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 Case 7Review Questions Click for Answers

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