Permanent pacemaker cycle length. Managent

It's presentation on permanent pacemaker cycle.
It's indication and contraindications.
Percutaneous and trans venous pacemaker indications and contraindications.
Different modes of permanent pacemaker like VVI, AAI and DDD etc.
How to diagnose and manage pacemaker problems.
Complications of permanent pacemaker

1. PACEMAKER TIMING CYCLES Dr Reema Qayoom CCEP Fellow

2. Outline: Pacing system Code Different Pacing modes Advantages and Disadvantages Single chamber timings Dual chamber timings Pacemaker mediated tachycardia Noise response Rate drop response therapy

3. TIMING CYCLE Timing cycle refers to beat to beat behavior of cardiac implantable electronic devices in response to intrinsic and paced beat. These timers can complete one of 2 tasks, Finish the cycle & completely timeout before restarting Restart if a native P or R wave is sensed

4. Interval denote the length of time between two events

5. PACING SYSTEM CODE

6. SINGLE CHAMBER PACING MODES

7. SINGLE CHAMBER ASYNCHRONOUS PACING AOO,VOO No intrinsic events are sensed Pacing occurs in the chamber independent of the intrinsic rhythm at lower rate interval or lower rate limit VOO mode can be temporarily enabled to prevent ventricular pacing inhibition from inappropriate oversensing of electromagnetic interference in a pacing dependent patient

8. DISADVANTAGE Potential risk of arrhythmia induction if the pacing stimulus falls in vulnerable period of myocardium

9. SINGLE CHAMBER INHIBITED PACING AAI,VVI When an intrinsic event is sensed, it results in inhibition of pacing AAI mode is indicated in patients with sinus node dysfunction but intact AV conduction VVI mode is most useful for patient with AF and slow ventricular rate VVI mode is also used for backup pacing in patients with an infrequent need for pacing

10. DISADVANTAGE AAI lacks ventricular pacing in the event of intermittent AV block VVI is associated with AV dyssynchrony (may manifest as pacemaker syndrome) VVI has higher incidence of atrial arrhythmia

11. SINGLE CHMABER TRIGGERED PACING AAT,VVT When the VVT mode is programmed, the sensing of a ventricular complex triggers an immediate pacing in the absolute refractory period of the ventricular myocardium (trigger) If no ventricular activity is sensed, pacing occurs at the programmed minimum rate This type of pacing mode is currently very seldom programmed in the long term since associated with an unnecessary increase in energy consumption.

12. Useful in the event of sensing of myopotentials or of electromagnetic interference: pacemaker does not inhibit but induces pacing on each artifact sensed outside the refractory period, which allows avoiding a pause in pacemaker-dependent patients This type of pacing mode was of particular interest in older pacemaker models which were more susceptible to external interferences since they only functioned in unipolar mode.

13. DISADVANTAGE Shortens battery life due to chronic pacing

14. DUAL CHAMBER PACING MODES

15. DUAL CHAMBER ASYNCHRONOUS PACING DOO Pacing pulse is delivered in the atrium, followed by a pacing pulse in the ventricle after completion of AV interval Transiently used in pacing dependent patients to avoid inappropriate pacing inhibition from EMI during surgeries or other interventions

16. DUAL CHAMBER TRACKING MODE DDD, VDD Capability to pace the ventricle in response to atrial events (tracking the atrial sensed events) An atrial sensed event inhibits pacing in atrium but triggers pacing in ventricle Termed P-synchronous pacing Most commonly used mode in dual chamber devices & in biventricular devices

17. Four faces of dual chamber pacing: AP-VP, AP-VS, AS-VP, AS-VS

18. VDD mode lacks atrial pacing Atrial tracking occurs when atrial rate is faster than LRL VVI pacing occurs at LRL when atrial rate is slower than LRL Used in single lead systems that integrates atrial sensing electrodes with a ventricular pace/sense electrode. VDD:

19. DUAL CHAMBER MODES WITHOUT TRACKING DDI, VDI, DVI DDI mode lacks P-synchronous pacing AV sequential pacing will only occur at the LRL if no ventricular event is sensed after the atrial paced event Commonly programmed as mode switch to prevent tracking of atrial tacyarrhythmias

20. DVI mode lacks atrial sensing It can be used in patients with marked sinus bradycardia or sinus arrest with atrial lead malfunction (oversensing) to provide AV synchrony If used in patients with normal sinus node function, asynchronous atrial pacing may precipitate AF

21. VDI mode lacks atrial pacing It essentially is the VVI mode with atrial sensing AV dissociation will occur with any pacing in this mode regardless of the atrial rate

22. DUAL CHAMBER TRIGGERED MODES DDT This mode involve ventricular triggering, atrial triggering or both Trigger pacing in the ventricle after sensed ventricular events ( ventricular triggering) to force CRT.

23. BENEFITS OF DUAL CHAMBER PACING Provides AV synchrony Lower incidence of atrial fibrillation Lower risk of systemic embolism and stroke Lower incidence of new congestive heart failure Lower mortality and higher survival rate

24. DISADVANTAGE OF DUAL CHAMBER PACING Requires at least two chamber lead system and has shorter battery longevity DDI: possible AV dyssynchrony and pacemaker syndrome ( doest not track atrial sensed events) VDI: AV dyssynchrony and potential atrial arrhythmias

25. SINGLE CHAMBER TIMING

26. Lower rate limit Upper rate (in rate responsive mode) Alert period Refractory period Absolute (Blanking) Relative Timing cycles in single chamber devices comprise these components

27. 1. LOWER RATE INTERVAL or LOWER RATE LIMIT It is the lowest rate at which the pacemaker will pace OR “It is the interval between successive pacing stimuli in the relevant chamber” LRI describes interval, whereas LRL describes the rate

28. Example: VVI 60 Device will maintain this rate when patient's intrinsic rate is <60 bpm A sensed or paced event resets the timer on the LRL interval at the rate it is programmed

29. UPPER SENSOR RATE INTERVAL Defines the shortest interval (highest rate) the pacemaker can pace as dictated by the sensor (AAIR, VVIR modes) The upper sensor rate interval in single chamber pacing is available only in rate-responsive mode The upper rate defines the limit at which sensor driven pacing can occur.

30. REFRACTORY PERIOD It is initiated by paced or sensed events After a sensed event, it prevents double counting the same event After paced event, it prevents sensing the paced stimuli Events within refractory period do not reset the LRL

31. REFRACTORY PERIOD Blanking period : 1 st portion of refractory period is termed blanking period Sense amplifier is turned off, and is therefore blind to any event that occur during this period “ Pacemaker is blind to any activity” Designed to prevent oversensing pacing stimulus

32. Unblanking period : second portion of refractory period is unblanking period Sense amplifier is active & is able to detect intrinsic events signals sensed in this period do not trigger or reset the LRI or AVI These sensed events are utilized for atrial tachyarrhythmia detection and mode switch, and used for noise response

33. VENTRICULAR REFRACTORY PERIOD There is ventricular refractory period on the ventricular channel Initial portion is ventricular blanking period VRP &VBP are triggered by ventricular paced (VP) or sensed (VS) events Following VS, VRP & VBP prevent repetitive sensing of same ventricular depolarization or repolarization potential (T wave) Following VP, they prevent sensing the pacing stimuli and T wave

34. ATRIAL REFRACTORY PERIOD There is ABP & ARP on the atrial channel Prevent repetitive counting of same atrial signal (following AS event) & prevent oversensing atrial pacing stimulus (following AP event )

35. ALERT PERIOD Remaining portion of LRI following the refractory period is Open interval or alert interval Open interval= LRI – Refractory period Events sensed during open interval reset the LRL

36. SINGLE CHAMBER RATE HYSTERESIS Hysteresis refers to adaptation of a timing interval in response to sensed intrinsic event Rate hysteresis refers to prolongation of the LRI following a sensed event to promote intrinsic rate Hysteresis interval is “the longer interval that is allowed in the presence of intrinsic rhythm”

37. Hysteresis tends to promote intrinsic rhythm and & minimize pacing If intrinsic activity is detected, the hysteresis interval remains in effect If no intrinsic activity is detected in a specific window, pacing resumes at the LRL

38. Automatic interval : The interval between two consecutive paced events is termed the automatic interval Escape interval : The interval between a sensed event & the next paced event is termed the escape interval

39. DUAL CHAMBER TIMING

40. DUAL CHMABER TIMING Due to complexity in dual chamber pacing, there are a number of extra timers involved in process Lower rate limit Upper rate limit AV and VA intervals Blanking and refractory periods

41. UPPER RATE INTERVAL Upper rate interval or upper rate limit determines the maximum paced ventricular rate in response to sensed atrial activity (also termed Maximum tracking rate) TARP=AVI+PVARP TARP is the limiting factor for URL

42. UPPER TRACKING RATE If the atrial rate begins to increase and continues to increase, it is not desirable to let the ventricle “track” to extremely high rates To limit the rate at which the ventricle can pace in the presence of high atrial rates, this limit is called the upper tracking rate OR The fastest rate at which atrial activity can be tracked 1:1 to the ventricle is termed upper rate limit or maximum tracking rate

43. UPPER RATE BEHAVIOUR When the intrinsic atrial rate approaches (and exceeds) the programmed upper rate, the pacemaker operation will change from 1:1 tracking operation to blocking operation which are designed to prevent tracking atrial arrhythmias which are too fast, and which will likely cause patient to become symptomatic Atrial rates above the URL can still be tracked , but the URL can not be violated by the device While tracking the atrial rates faster than the URL, the successive ventricular paced beats are delayed (i.e. the AVI is prolonged)so that the ventricular rate never exceeds the URL

44. As the AVI is prolonged on successive beats, each successive atrial sensed event occurs closer and closer to preceding ventricular paced beat, until an atrial event eventually falls within the PVARP and is not tracked The subsequent atrial activity is tracked again without any AVI prolongation and the process repeats This pattern is termed “ Pacemaker pseudo-AV wenckebach or Pacemaker wenckebach upper rate response”

45. As the atrial rate increases during pacemaker wenckebach behavior, the maximum paced ventricular rate remains constant at the URL but the wenckebach ratio progressively increases (the pauses become more frequent) As the intrinsic atrial rate continues to increase, the A-A interval eventually becomes shorter than the TARP,at which point every other P wave falls within the PVARP and is not tracked , resulting in 2:1 tracking

46. WENCKEBACH VS 2:1 BLOCK If the upper tracking rate interval is longer than the TARP, the pacemaker will exhibit Wenckebach behavior first If the TARP is longer than upper tracking rate, then 2:1 block will occur

47. REMEMBER 1:1 tracking occurs whenever the patient’s atrial rate is below the upper tracking rate (assuming the TARP is less than the upper tracking rate) Wenckebach will occur when the atrial rate exceeds the upper tracking rate limit (and is longer than the TARP) Atrial rate greater than TARP causes 2:1 block

48. What can we do to make Wenckebach occur first? Going to 2:1 block first without a Wenckebach period may not be the optimal situation because many patients do not tolerate a precipitous drop in ventricular rate well Shorten or reduce the TARP by Shortening the PVARP Shortening the SAV Programming rate adaptive AV

49. ATRIOVENTRICULAR INTERVAL/ AV DELAY AVI or AVD is programmable interval triggered by sensed or paced atrial events Terminated by ventricular sensed event (VAI initiates) If no ventricular event is sensed, a ventricular pacing stimulus is delivered at the end of AVI It is designed to mimic native PR interval Hemodynamic benefit of AV synchrony is diminished in patients with PR interval > 220ms Doppler echocardiography may be required to determine optimal AV delay for particular individual

50. DIFFERENTIAL ATRIOVENTRICULAR INTERVAL The sensed AVI is typically shorter than paced AVI, this is called differential AVI or sensed AV offset. The paced AVI starts with the atrial pacing With atrial sensing, the impulse typically starts in sinus node & is on its way to the AV node as it reaches the atrial lead. The event is therefore sensed on atrial lead about 20-50ms after the onset of P wave. The sensed AVI is therefore programmed shorter than the PAV

51. DYNAMIC OR RATE ADAPTIVE ATRIOVENTRICULAR INTERVAL Permits modulation of the sensed or paced AVI based on heart rate either intrinsic or sensor driven The shortening of AVI with exercise mimics normal physiologic shortening of PR interval to provide optimal AV synchrony.

52. ATRIOVENTRICULAR INTERVAL HYSTERESIS Alteration in paced AVI relative to patient’s intrinsic AV conduction POSITIVE HYSTERESIS : a longer AVI is permitted to allow maintenance of intrinsic AV conduction NEGATIVE HYSTERESIS : Intended to temporarily shorten the AVI if an intrinsic ventricular event is sensed in AVI, which could be relevant to biventricular pacing or treatment of HCM .

53. VENTRICULAOATRIAL INTERVAL Also called Atrial escape interval “Interval from ventricular sensed or paced event to atrial paced event” The VA interval is the longest period that may elapse after a ventricular event before the atrium must be paced in the absence of atrial activity VA interval= LRI –PAV interval

54. CROSS CHAMBER BLANKING & REFRACTORY PERIOD Essential to prevent cross talk “Cross talk refers to sensing events from another chamber “ AV cross talk refers to sensing atrial events (atrial pacing stimulus or its afterpotential) on the ventricular channel and can potentially cause asystole in pacing dependent patients VA cross talk refers to sensing ventricular events (pacing stimulus, QRS, T wave) on the atrial channel Cross talk is commonly used for AV cross talk VA cross talk is loosely termed far field R wave (FFRV )oversensing

55. SOLUTION OF CROSSTALK Elimination of cross talk can be achieved by Extending the PAVB Decreasing atrial output Reducing ventricular sensitivity

56. ATRIAL CHANNEL INTERVALS POST VENTRICULAR ATRIAL BLANKING PERIOD (PVAB) PVAB is initiated by ventricular activity It ensures that the device’s atrial channel doesn’t sense or respond to signals generated The purpose of PVAB is to prevent sensing the ventricular beat in the atrium

57. POST VENTRICULAR ATRIAL REFRACTORY PERIOD (PVARP): following VS or VP event, PVARP is triggered on the atrial channel PVARP & PVAB prevent VA crosstalk. PVARP should ideally prevent oversensing any retrograde P wave Any atrial beat falling into PVARP is noted as AR, but not used from a timing diagram standpoint Too short PVARP may cause a retrograde P wave to be sensed beyond PVARP which can initiate a pacemaker reentrant tachycardia or endless loop tachycardia Too long PVARP results in loss of atrial tracking (sinus P wave may fall within it)

58. TOTAL ATRIAL REFRACTORY PERIOD( TARP): TARP is defined as the SAV+PVARP No atrial beats can be tracked within this interval If any atrial beat falls into this interval, this is not tracked When the atrial rate reaches TARP rate, the pacemaker exhibits a 2:1 block behavior.

59. VENTRICULAR CHANNEL INTERVALS POST ATRIAL VENTRICULAR BLANKING PERIOD (PAVB ) is enabled on the ventricular channel following paced but not sensed atrial events. (b/c intrinsic atrial activity are unlikely to result in crosstalk) The purpose of this interval is to prevent sensing in the ventricle after an atrial paced beat

60. VENTRICULAR BLANKING PERIOD (VB) This is to prevent sensing the VP or the ventricular depolarization after it has already been sensed VENTRICUALR REFRACTORY PERIOD A period of time during which ventricular sensed events are ignored for timing purpose, but included in diagnostic counters. This prevents falsely sensing R-wave and T-waves , which could cause timing errors

61. AV CROSS TALK & VENTRICULAR SAFETY PACING One of the most serious consequence of cross talk in dual chamber pacemaker is sensing of far field atrial stimuli on ventricular channel, resulting in ventricular pacing inhibition & asystole in pacing dependent patient To counteract this, atrial pacing output triggers 2 periods on ventricular channel during AVI

62. 1 st is PAVB, ,during which ventricular sense amplifier is turned off Immediately following this, there is VSP window (CDW) during which ventricular sense amplifier is active Signals sensed during crosstalk sensing window are considered non physiologic b/c of close coupling interval to atrial stimulus (oversensing of atrial pacing afterpotential, PVC or noise) Signals sensed during this window does not cause pacing inhibition, but rather trigger delivery of ventricular pacing output at an abbreviated AVI usually around 110ms The shortened AVI makes the identification of VSP

63. PACEMAKER MEDIATED TACHYCARDIA Only occurs in dual chamber tracking modes in patients with intact AV conduction Retrograde VA conduction serves as the retrograde limb The retrograde P wave is sensed and tracked by the pacemaker which forms the antegrade limb of circuit

64. For termination of PMT , devices may extend the PVARP for one cycle ( so that the retrograde P wave falls within the extended PVARP and is not tracked or withhold VP for one cycle

65. NOISE RESPONSE Noise refers to nonphysiologic signals that are sensed by the device Noise can be due to EMI, lead malfunction or device header issues Noise can lead to pacing inhibition or rapid pacing in pacemakers, inappropriate tachycardia detection and therapies in ICDs . The unblanked portion of refractory period is utilized for noise detection

66. Sustained EMI results in repetitive retriggering of the RP resulting in asynchronous pacing (NOISE REVERSION) In other devices (St jude , Boston)a portion of refractory period , called noise sampling period or noise sampling window, is initiated for noise detection. Repetitive retriggering of NSP leads to asynchronous pacing

67. ISSUE: NEUROCARDIOGENIC SYNCOPE Hypersensitive carotid sinus syndrome Vasovagal syncope

68. RATE DROP RESPONSE THERAPY Rate drop response therapy can be used for CSS and VVS patients for whom a PPM is indicated It includes the steps The pacemaker looks for a drop in heart rate (detection cycle) The pacemaker looks for that rate to remain low to confirm that it is indeed a rate drop episode (confirm cycle) The pacemaker intervenes at a high pacing rate that is separate from the programmed lower rate or upper rate (intervention cycle) When an episodic drop in heart rate occurs and is detected and confirmed, RDR therapy provides an immediate increase in the pacing rate for a specified period, and then gradually slows pacing to resynchronize to the sinus rate