心臟植入性電子儀器(CIED)的基本原理及設定

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心臟植入性電子儀器(CIED)的基本原理及設定

  1. 1. 植入性心臟電子儀器(CIEDs) 的基本原理及設定 高雄長庚醫院 心臟內科 陳煌中 醫師 2013.10.19 (W6) 蓮潭會館
  2. 2. Outlines • Introduction of CIEDs (cardiovascular implantable electronic devices) • General Setting of PPM – Pacing, sensing, capture – Low rate, upper rate – Pacing mode – Refractory and blanking period – Other setting
  3. 3. Reference
  4. 4. Cardiac Conduction Review Atria SA node Ventricles AV node Bundle branches
  5. 5. Implantable Pacemaker System Lead wire(s) Implantable pulse generator (IPG) • Battery • Circuitry • Connector(s) Connector Block Circuitry Battery Myocardial tissue
  6. 6. Lead Characterization Passive Fixation Leads Active Fixation Leads Epicardial Leads Bipolar coaxial lead
  7. 7. Characteristics of an Electrical Circuit • Voltage (V) – Voltage is the force, or “push,” that causes electrons to move through a circuit – Provided by the pacemaker battery • Current (I) – Determined by the amount of electrons that move through a circuit – Cause myocardial cells to depolarize • Impedance (R or W) – The opposition to current flow – All resistance: conductor, electrode, myocardium V I R
  8. 8. Battery Capacity and Longevity
  9. 9. Battery Capacity and Longevity
  10. 10. Voltage and Current Flow Electrical Analogies Spigot (voltage) turned up, lots of water flows (high current drain) Water pressure in system is analogous to voltage – providing the force to move the current Spigot (voltage) turned low, little flow (low current drain)
  11. 11. Lead Impedance, 300~1500 Ohm High impedance Conductor failure, impedance >2500 Ohm Low impedance Insulation defect, Impedance <300 Ohm
  12. 12. The Revised NASPE/BPEG Generic (NBG) Code for Antibradycardia Pacing I II III IV V Chamber(s) Paced Chamber(s) Sensed Response to Sensing Rate Modulation Multisite Pacing O = None O = None O = None O = None O = None A = Atrium A = Atrium T = Triggered R = Rate A = Atrium V = Ventricle V = Ventricle I = Inhibited D = Dual (A + V) D = Dual (A + V) D = Dual (T + I) modulation V = Ventricle D = Dual (A + V) S = Single (A or V) S = Single (A or V) NASPE is the North American Society of Pacing and Electrophysiology BPEG is the British Pacing and Electrophysiology Group BERNSTEIN, et al.; PACE 2002; 25:260–264
  13. 13. Which mode is appropriate? Indication • DDD(R) • complete AV block • sinus nodal dysfunction • paroxysmal atrial fibrillation • AAI(R) • sinus nodal dysfunction • VVI(R) • permanent atrial fibrillation AAI/AAIR DDD/DDDR VVI/VVIR
  14. 14. Optimal Pacing Mode in Sinus Node Disease and AV Block 2013 ESC Guidelines on cardiac pacing and cardiac resynchronization therapy
  15. 15. Programmability
  16. 16. General Setting of Pacemaker Parameter Base Rate Description Pacing timing cycle Maximum Sensor Rate (MSR) is the Max. highest pacing rate Sensor rate allowed by ratemodulated pacing Max Tracking Rate upper limit of the ventricular pacing rate in response to the patient’s intrinsic atrial activity Setting Recommendation •Depends on patient’s need Hysteresis •Nominal setting 60-70 bpm Rest rate •Depends on patient’s age and activity (220-Age)X0.85 •Depends on patient’s age and activity (220-Age)X0.85 •Also has to consider the other cardiac disease
  17. 17. General Setting of Pacemaker Parameter Description Setting • AVB : 200-150 • SSS : depends on the AV conductivity, nominal less than 300ms Recommendation Reduce unnecessary ventricular pacing  VIP/AICS/AV hysteresis /MVP AV/PV delay AV : internal of Ap to Vp PV : interval of As to Vp Rate responsive AV/PV delay shorten AV/PV Delay when the atrial rate is higer then 90 bpm, to mimic physical Off, slow, mid, high demand, also allows setting higher MTR Pulse Amplitude, Pulse width (A, V) determines how much electrical potential is applied to the myocardium during the pacing stimulus Nominal setting 2.5V@0.4ms • 2-3 times of threshold to secure capture • AutoCapture A/V sensitivity This parameter determines the amplitude of signals to which the device’s sense amplifiers will respond • A : 0.5~1.0 mV • V : 2~3 mV Higher level indicate less sensitive to P/R wave
  18. 18. Pacemaker Code • Very useful in helping you understand how the IPG is interpreting events • Code: – AS  Atrial Sense – AP  Atrial Pace – AR  Atrial Refractory – VS  Ventricular Sense – VP  Ventricular Pace – VR  Ventricular Refractory
  19. 19. Sensing, Pacing, Capture
  20. 20. Pacemaker Sensing
  21. 21. Sensing Threshold
  22. 22. Output Pulse of Pacemaker
  23. 23. Pacing Threshold Pulse Amplitude and Width (Duration) No Capture! No Capture!
  24. 24. Strength – Duration Curve
  25. 25. Safety Ratio for Capture
  26. 26. Safety Ratio for Capture
  27. 27. Automatic Stimulation Threshold Search
  28. 28. Lower rate, Rest rate, Upper rate
  29. 29. Lower Rate Interval (LRI) - VVI • The lowest rate the pacemaker will pace the heart in the absence of intrinsic events LRI LRI
  30. 30. Hysteresis • Allows the rate to fall below the programmed lower rate following an intrinsic beat 60 bpm 50 bpm
  31. 31. Rest Rate • Allows the pacemaker to decrease the base rate to • • the programmed auto rest rate during periods of inactivity. People spend about 7 hours, out of a 24 hour day, sleeping, therefore 29% of the time is spent sleeping. The pacemaker calculates where this 29% would occur based on the Activity Variance Histogram and establishes this point as threshold.
  32. 32. “R” = Rate Response • When the need for oxygenated blood increases, the pacemaker ensures that the heart rate increases to provide additional cardiac output.
  33. 33. Rate-Adaptive Pacing
  34. 34. Rate-Adaptive Pacing: Accelerometer Accelerometer • • • • • • Low current drain Easy to manufacture Rapid response to onset of activity Compatible with standard pacing leads Not responsive to pressure applied to can Used in all current St. Jude Medical pacemakers (began with Trilogy DR+) Circuit Board
  35. 35. Rate-Adaptive Pacing • The Sensors—Physiology – Evoked response • The QRS depolarization decreases in area with exercise • Works only when the device is pacing – QT interval • QT interval shortens with exercise • Works only when the device is pacing
  36. 36. Rate-Adaptive Pacing: St. Jude • Reactive time and recovery time
  37. 37. Upper Rate Response • Dual-chambers pacemakers try to maintain 1:1 AV synchrony but this is not always possible • In the presence of high intrinsic atrial rates, pacemakers may revert to upper rate responses
  38. 38. Upper Sensor Rate • Defines the shortest interval (highest rate) the pacemaker can pace as dictated by the sensor (AAIR, VVIR modes)
  39. 39. Tracking
  40. 40. Upper Tracking Rate (UTR) • The maximum rate the ventricle can be paced in response to sensed atrial events Lower Rate Interval { Upper Tracking Rate Limit SAV AS VP VA SAV AS VA VP DDDR 60 / 100 (upper tracking rate) Sinus rate: 100 bpm
  41. 41. Upper Rate Behavior Ventricular Rate UTR LR 1:1 Atrial Tracking No Ventricular Pacing LR = Ventricular Pacing Wenckebach UTR Atrial Rate TARP 2:1 Block
  42. 42. Wenckebach Operation DDD / 60 / 120 / 310
  43. 43. 2:1 Block DDD / 60 / 120 / 310
  44. 44. Upper Rate Behavior – 2:1 Block
  45. 45. 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 (total atrial refractory period) is longer than the upper tracking rate interval, then 2:1 block will occur.
  46. 46. Pacing Mode
  47. 47. AAI Mode
  48. 48. VVI Mode
  49. 49. DDD Mode
  50. 50. 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 rates
  51. 51. The Magnet Test (VOO Mode)
  52. 52. Magnet ECG – St. Jude
  53. 53. Magnet ECG – Medtronic
  54. 54. Refractory & Blanking Period
  55. 55. Blanking and Refractory Periods • Blanking Period – A period of time during which the sense amplifiers are off, and the pacemaker is “blind”. – Designed to prevent oversensing pacing stimulus • Refractory Period – A period of time during which sensed events are ignored for timing purposes, but included in diagnostic counters – Designed to prevent inhibition by cardiac or noncardiac events
  56. 56. Why Do We Use Refractory and Blanking Periods? • Pacemaker sensing occurs when a signal is large enough to cross the sensing threshold 5.0 mV Sensing does not tells us anything about the origin or morphology of the sensed event, only its “size.” 2.5 mV 1.25 mV 1.25 mV Sensitivity Time
  57. 57. Why Do We Use Refractory and Blanking Periods? • By manipulating the sense amplifiers, we filter signals based on their relationship The potential for digitizing these signals may someday allow pacemakers to discriminate signals based on morphology rather than just on their relationship. 5.0 mV 2.5 mV SENSE! 1.25 mV Sensing Blanking Time Refractory
  58. 58. Blanking Periods • Atrial Blanking (AB) – A non-programmable atrial blanking period (50-100 ms) from atrial paces or senses. – Avoid the atrial lead sensing its own pacing pulse or P wave (intrinsic or captured). • Ventricular blanking (VB) – 50-100 ms in duration and is dynamic, based on signal strength. – After a ventricular paced or sensed event to avoid sensing the ventricular pacing pulse or the R wave (intrinsic or captured). • Post ventricular atrial blanking (PVAB) – Initiated by a ventricular pace or sensed event (220 ms) – Avoid the atrial lead sensing the far-field ventricular output pulse or R wave.
  59. 59. Ventricular Blanking • The first portion of the refractory period • Pacemaker is “blind” to any activity • Designed to prevent oversensing pacing stimulus Lower Rate Interval VP Blanking Period Refractory Period VP VVI / 60
  60. 60. Blanking Periods Ventricular Refractory and Blanking Periods PVAB ARP Post Atrial Ventricular Blanking PVARP VRP Ventricular Refractory Period Ventricular Blanking
  61. 61. AV Crosstalk • Atrial pacing spike will be detected in the ventricle. • Will inhibit ventricular pacing
  62. 62. Add PAVB to Prevent AV Crosstalk
  63. 63. Blanking Periods Atrial Refractory and Blanking Periods Post Ventricular Atrial Blanking Atrial Blanking PVAB ARP PVARP VRP Atrial Refractory Period Post Ventricular Atrial Refractory Period
  64. 64. Refractory Periods • VRP and PVARP are initiated by sensed or paced ventricular events. – The VRP is intended to prevent self-inhibition such as sensing of T-waves. – The PVARP is intended primarily to prevent sensing of retrograde P waves, far-field R wave, or premature atrial contractions.
  65. 65. Ventricular Refractory Period 1000 ms 1000 ms VRP 320 ms Blanking V P VRP 320 ms V R V P Refractory • Pacemaker VRP avoids the sensing of : – – – – – Its own stimulus The paced QRS complex The T wave (Excessive) afterpotential The combination of T wave and afterpotential V R
  66. 66. Pacemaker Mediated Tachycardia (PMT)
  67. 67. Evaluation of Retrograde VA Conduction PVARP
  68. 68. Prevention of PMT • Prevention – Extend PVARP (Post Ventricular Atrial Refractory Period) – Program PVARP 50 ms longer than measured retrograde VA conduction (RVAC) • Use VVIR mode to determine the RVAC
  69. 69. Algorithms for automatic Termination of PMT
  70. 70. AV Delays
  71. 71. The 4 Fundamental Timing Cycle of a DDD Pacemaker
  72. 72. AV Delay or AV Interval (AVI) • AVI is the interval between an atrial event (either sensed or paced) and the scheduled delivery of a ventricular stimulus. • Typical sAVI is 30-50 ms shorter than pAVI (sAVI < pAVI). • The AV intervals may be programmed to fixed values or rate-adaptive (i.e. shortening with increasing atrial rates).
  73. 73. The Rate-Adaptive Interval • The rate-adaptive AV interval mimics the physiologic response of the heart.
  74. 74. The 4 Fundamental Timing Cycle of a DDD Pacemaker
  75. 75. Other Setting
  76. 76. Automatic Mode Switching (AMS) • AMS turns off atrial tracking in the presence of intrinsic atrial activity above a programmable atrial rate cutoff. • Mode will switch from tracking mode (DDDR, DDD) to DDIR (non-tracking mode) when atrial arrhythmia is detected. • AMS can cause a sudden rate decrease as atrial tracking. • Ventricular pacing is decoupled from atrial events, but rate responsive pacing is matched to metabolic needs.
  77. 77. Mode Switch • The device detects an atrial arrhythmia by constantly comparing intervals with the programmed mode switch detection rate. MS DDD / 60 / 120 Mode Switch ON
  78. 78. 減少右心室電刺激 = 減少心衰竭住院 及心房顫動 Risk of AF Relative to DDDR Patient With Cum%VP=0 MOST study Every incremental 1% of unnecessary VP increases the risk for Heart Failure Hospitalizations by 5.4% There is a 1% increase in the risk of AF for each 1% increase in cumulative right ventricular pacing. Within 95% Confidence Risk of AF Cumulative % Ventricular Pacing
  79. 79. Ventricular Intrinsic Preference (VIP) • VIP activation – Device extends AV delays by 160 ms searching for Rwaves for up to 3 cycles in our example – R-waves found within 1 cycle, therefore, AV delay remains at lengthened value
  80. 80. Ventricular Intrinsic Preference (VIP) • VIP deactivation – Device extends AV delays by 160 ms searching for Rwaves for up to 3 cycles in our example – No R-waves found within 3 cycle, therefore, AV delays returns to programmed values. 1 2 3
  81. 81. Ventricular Intrinsic Preference (VIP) • VIP most beneficial – – Intermittent AV block Mild prolongation of AV conduction • VIP not beneficial – – – Complete permanent AV block Marked 1st degree AV block If CRT therapy is indicated • VIP clinical benefits – Less risk of heart failure progression – Less risk of developing AF – Better QoL trough improved hemodynamics
  82. 82. MVP AAI (R) to DDD(R)Pacing (MVP) Managed Ventricular Operation Switch from AAI(R) to Temporary DDD(R) Mode Ventricular support if loss of A-V conduction is persistent. 2 out of 4 Most Recent A-A Intervals with No Conducted VS Event No VS Conduction Ventricular Back-Up Pace at 80 ms Post the Scheduled AP Switch to DDD(R) occurs after back-up VP; programmed PAV/SAV are used during this mode of operation
  83. 83. Intracardiac Defibrillator (ICD) Dual Coil Lead Single Coil Lead Cold Can Proximal Shock Electrode Hot Can Distal Shock Electrode
  84. 84. Cardiac Resynchronization Therapy Goal: Mitigate dyssynchrony through atrial synchronous biventricular pacing Right Atrial Lead Left Ventricular Lead Right Ventricular Lead • LV lead site: lateral = posterior > apical • OptiVol thoracic impedance (MID-HeFT study): 和PCWP成反比
  85. 85. Thank You for Your Attention! Have a Nice Weekend~

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