植入性心臟電子儀器(CIED )的基本原理及設定_20130907北區

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植入性心臟電子儀器(CIED )的基本原理及設定_20130907北區

  1. 1. 植入性心臟電子儀器地基本原 理與設定 林口長庚 巫龍昇醫師
  2. 2. Voltage, Current, and Impedance Recap • Voltage: The force moving the current (V) – In pacemakers it is a function of the battery chemistry • Current: The actual continuing volume of flow of electricity (I) – This flow of electrons causes the myocardial cells to depolarize (to “beat”) • Impedance: The sum of all resistance to current flow (R or W or sometimes Z) – Impedance is a function of the characteristics of the conductor (wire), the electrode (tip), and the myocardium 2
  3. 3. Voltage and Current Flow Electrical Analogies Spigot (voltage) turned up, lots of water flows (high current drain) Spigot (voltage) turned low, little flow (low current drain) Water pressure in system is analogous to voltage – providing the force to move the current
  4. 4. Resistance and Current Flow Electrical Analogies • Normal resistance – friction caused by the hose and nozzle More water discharges, but is all of it going to the nozzle? • High resistance – a knot results in low total current flow • Low resistance – leaks in the hose reduce the resistance
  5. 5. Ohm’s Law • Describes the relationship between voltage, current, and resistance • V = I X R • I = V / R • R = V / I V I R V R I V R I R V I = = = X
  6. 6. Other terms • Cathode陰極: – For example, the electrode on the tip of a pacing lead • Anode陽極: – Examples: • The “ring” electrode on a bipolar lead • The IPG case on a unipolar system 6 Anode Cathode
  7. 7. PACING MODES Pacing Modes
  8. 8. I II III IV Chamber(s) Paced Chamber(s) Sensed Response to Sensing Rate Modulation O = None A = Atrium V = Ventricle D = Dual (A + V) S = Single (A or V) O = None A = Atrium V = Ventricle D = Dual (A + V) S = Single (A or V) O = None T = Triggered I = Inhibited D = Dual (T + I) O = None R = Rate modulation Pacemaker modes most often seen: DDDR/VDD VVIR AAIR->DDDR (MVP) What mode would you use for 3rd Degree Block? What mode would you use for SSS? What mode would you use for permanent AF?
  9. 9. Knowledge Checkpoint What is the rhythm? What type of device does this patient need?
  10. 10. VVI Mode I II III Chamber(s) Paced Chamber(s) Sensed Response to Sensing O = None A = Atrium V = Ventricle D = Dual (A + V) S = Single (A or V) O = None A = Atrium V = Ventricle D = Dual (A + V) S = Single (A or V) O = None T = Triggered I = Inhibited D = Dual (I + T)
  11. 11. VVI Example • Chamber paced: Ventricle • Chamber sensed: Ventricle • Response to sensing: Inhibition –VVI 60 = Lower Rate timer of 1000 ms • Pacing every 1 second if not inhibited V P V P V P Lower Rate Timer 1000 ms Lower Rate Timer 1000 ms Lower Rate Timer ….
  12. 12. VVI Example (60 bpm) V P V S V P V P Lower rate timer 1000 ms x Lower rate timer 1000 ms •Paces and Senses in the ventricle •Timed from each QRS •If it sees a sensed event, it will inhibit the next pace
  13. 13. VOO Mode – Asynchronous Pacing Chamber paced: Ventricle Chamber sensed: None Response to sensing: None The intrinsic ventricular event cannot be sensed, and thus, does not interrupt the pacing interval. 1000 ms1000 ms 1000 ms V P V P V P V P VOO results in fixed-rate pacing in the ventricle.
  14. 14. Knowledge Checkpoint What is the rhythm? What type of device does this patient need?
  15. 15. AAI Mode I II III Chamber(s) Paced Chamber(s) Sensed Response to Sensing O = None A = Atrium V = Ventricle D = Dual (A + V) S = Single (A or V) O = None A = Atrium V = Ventricle D = Dual (A + V) S = Single (A or V) O = None T = Triggered I = Inhibited D = Dual (I + T)
  16. 16. AAI • Paces in the atrium • Timed from last P wave Pacing Interval A P A P Lower Rate Timer 1000 ms
  17. 17. Knowledge Checkpoint What is the rhythm? What type of device does this patient need?
  18. 18. DDD Mode I II III Chamber(s) Paced Chamber(s) Sensed Response to Sensing O = None A = Atrium V = Ventricle D = Dual (A + V) S = Single (A or V) O = None A = Atrium V = Ventricle D = Dual (A + V) S = Single (A or V) O = None T = Triggered I = Inhibited D = Dual (I + T)
  19. 19. DDD A S V P A S V P A P V S A P V S • Senses and paces in both chambers when needed
  20. 20. Knowledge Checkpoint A B C D Label each EKG with the faces of pacing (AS-VS, AP-VS, AP-VP, AS-VP).
  21. 21. Magnet Application for devices • Magnet application temporarily changes pacing mode to DOO/VOO Magnet Applied 1 2 3 1 0 0 1 0 0 1 0 0
  22. 22. The 4th letter: “R” • Question: what does your heart rate do when you exercise? • “R” means “Rate response” • Pacemaker will increase pacing rate in response to exercise – if patient does not increase his own rate
  23. 23. General guidelines for programming common pacemaker parameter parameter situation Chronic setting comments Lower rate limit General : minimal pacing desired; 50-70bpm 40-60bpm Use rate hysteresis Upper rate limit General Child/athletes CAD/angina 85% maximal predicted HR 0.85*(220-age) (220-age) bpm 110-120bpm Based on average levels of activity May require programing short refractory periods Approximates peak HR on maximal beta blocker
  24. 24. Rate hysteresis
  25. 25. General guidelines for programming common pacemaker parameter parameter situation Chronic setting comments Pacing output Fixed voltage Fixed pulse width 3-4 X pulse width threshold 2-3X voltage threshold Minimizing voltage output more efficient Use autothreshold function sensitivity Atrium ventricle 25-50% threshold 25-50 % threshold Need <1mV setting for mode switching Evaluate oversensing in unipolar system
  26. 26. General guidelines for programming common pacemaker parameter parameter situation Chronic setting comments AV delay AV block Intrinsic conduction (no HF) Intrinsic conduction (CHF) 150-180msec paced AV delay, sensed AV delay 25-50msec <paced AV delay Up to 220msec Often set even longer AV delay Turn on rate adaptive AV delay in active patients Longer AV delay may compromise hemodynamics, use AV hysteresis to promote intrinsic conduction Paced induced dyssynchrony of very long AV delay Optimize by doppler,
  27. 27. AV hysteresis
  28. 28. Programmer
  29. 29. Programmer - PAV, SAV
  30. 30. Programmer - Mode Switch
  31. 31. ICD Function What is the function of an ICD? • Sense cardiac rhythms • Detect arrhythmias • Deliver therapy • Pace when necessary
  32. 32. Typical Transvenous Lead
  33. 33. Transvenous Leads Placement Single Coil Dual Coil
  34. 34. ICD Therapies • Tachyarrhythmia Therapy –Cardioversion (CV)Sychronized ro R –Anti-Tachycardia Pacing (ATP) –Defibrillation Shock Low Power oBradyarrhythmia Therapy –Pacing Modes Low Power High Power High Power
  35. 35. Bradyarrhythmia Therapy • Most ICDs offer: –Single Chamber Pacing • AAI(R), VVI(R) and VOO –Dual Chamber Pacing • DDD(R), DDI(R), DOO and ODO • Mode Switch –Separate post-shock pacing programming • Ensures capture
  36. 36. ICD common setting • VT zone 160-200bpm • VF zone >200bpm • The rate usually set 10bpm slower than the documented ventricular arrhythmia rate to reliable detection • Ventricular sensitivity must allow for the detection of very low amplitude ventricular fibrillation signals and typically set to 0.3 mV
  37. 37. ICD basic parameters parameter function programming comment VF zone Detection rate for fastest VF zone: rate of VF zone must be on VF zone; Hemodynamically unstable VT Must be on at all times, only shock Rx available VT zone Detection rate for slower VTs in multizone programming On or off; Usually 10bpm < spontaneous VT ATP and cardioversion Rx available Initial detection No. of intervals VF zone : 75% intervals > VF rate VT zone: number of consecutive intervals > rate limit VF typically 12/16, or 18/24 beats > VF rate VT typically 8-20 beats >VT rate
  38. 38. ICD basic parameters parameter function programming comment Ventricular sensitivity Usually 0.18-0.3mV High sensitivity needed to detect small EGM in VF ATP Painless pace termination of VT On or off Often initial RX for VTs <200bpm Type of sequence (burst or ramp) Burst: all paced intervals the same Ramp: decrements between paced intervals in sequence Burst or ramp Ramp therapy considered more aggressive but equal efficacy for spontaneous
  39. 39. ICD basic parameters parameter function programming comment Cardioversion/defib rillation Shock therapy Always on in all zones Only RX in VF, or single zone; initial RX or follows ATP in VT zones Energy Magnitude of shock in joules VF: DFT =5-10 J VT: at or above smallest successful energy VT often terminated with 2- 10 J
  40. 40. 41 • 13% - 38% of ICD patients experience significant levels of psychological stress related to the fear of receiving a shock.6 • Patients receiving shocks reported feeling less healthy, had lower levels of psychological well-being, and reduced physical and emotional function.7 • Shock therapy is inversely correlated with quality-of-life.8,9 • Patients receiving ATP first showed a significant increase in QOL over those receiving shock first.10 Shock Therapy is Related to a Decrease in QOL 6. Hammil SC, et al. J Cardiovasc Electrophysiol, 2000. 7. Namerow PB, et al. PACE, 1999. 8. Carroll DL, et al. Heart Lung, 2005. 9. Irvine J, et al. Am Heart J, 2002. 10. Wathen MS, et al. Circulation, 2004.
  41. 41. Shock Reduction • Anti-tachycardia pacing • 延長VT/VF偵測 • 藥物
  42. 42. Anti-Tachycardia Pacing Re-entry initiated ATP delivered at a rate faster than tachyarrhythmia. Wavefronts collide. Subsequent Pulse: Wavefronts collide closer to re-entry circuit Subsequent Pulses: Wavefronts collide even closer to re-entry circuit Arrhythmia terminated
  43. 43. Anti-tachycardia pacing (ATP)
  44. 44. ATP的風險
  45. 45. Anti-tachycardia pacing(ATP) Burst v.s Ramp Programmed Values: Number of S1 Pulses = 4 Number of Sequences = 4 R- S1% = 91% (less agrassive) Decrement* = 10 ms * Decrement between sequences Programmed Values: Number of S1 Pulses = 4 Number of Sequences = 4 R-S1% = 91% (less aggrassive) Decrement* = 10 ms * Decrement between pulses * Adds a pulse per sequence PITAGORA ICD study: Bust is significantly more efficacious than ramp in terminating FVT episodes
  46. 46. Sensing • Sensing is: –The process of identifying cardiac depolarizations from an intracardiac electrogram Measured Peak-to-Peak >5 mV for optimal sensing
  47. 47. Detection • Measured in: –Beat-to-beat intervals (milliseconds), or –Beats-per-minute (BPM) Detection Rate •Classifies rhythm by detection zone: –VT = Ventricular Tachycardia +/- FVT –VF = Ventricular Fibrillation •Programmable in ranges of rates Example:VT = 162 bpm – 188 bpm VF = 188 bpm and faster
  48. 48. Detection Zone Classifications
  49. 49. ICDexample
  50. 50. Detection • Measured in: – Number of intervals to detect (NID), or – Length of time to detect •Programmable by: – Beat or interval counters • Consecutive ex: 16 beats within the detect zone • Probabilistic (percentage or fraction) ex: 12 out of 16 beats within the detect zone – Time in seconds Detect Duration
  51. 51. Detection Used for detection of VT Consecutive Counter
  52. 52. Detection NID = 12/16 Probabilistic Counter
  53. 53. • Can you identify the detect zones? • Name the rate & duration for each Detection Detect Zones
  54. 54. Cardioversion • Delivers shock on an R-wave • Aborts if synchronization cannot be obtained due to arrhythmia termination
  55. 55. Cardioversion
  56. 56. Defibrillation Programming *Medtronic Programming Screen
  57. 57. Major Challenges Faced • Inappropriate therapies • Unnecessary shocks • Repetitive shocks 58
  58. 58. 59 • 13% - 38% of ICD patients experience significant levels of psychological stress related to the fear of receiving a shock.6 • Patients receiving shocks reported feeling less healthy, had lower levels of psychological well-being, and reduced physical and emotional function.7 • Shock therapy is inversely correlated with quality-of-life.8,9 • Patients receiving ATP first showed a significant increase in QOL over those receiving shock first.10 Shock Therapy is Related to a Decrease in QOL 6. Hammil SC, et al. J Cardiovasc Electrophysiol, 2000. 7. Namerow PB, et al. PACE, 1999. 8. Carroll DL, et al. Heart Lung, 2005. 9. Irvine J, et al. Am Heart J, 2002. 10. Wathen MS, et al. Circulation, 2004.
  59. 59. 辛苦了 謝謝聆聽
  60. 60. Differentiation of SVT from VT parameter What It does Potentially useful For Potential problem stability Suppressed therapy for tachyarrhythmia with variable ventricular rate Atrial fibrillation Underdetection of VT with irregular rate; failure to suppress therapy for SVTs with regular ventricular response onset Suppressed therapy for tachyarrhythmia that slowly accelerate Sinus tachycardia Underdetection of gradually accelerating VT or VT onset during sinus tachycardia; failure to suppress therapy for sudden onset SVT Ventricular electrogram width Suppress therapy for tachyarrhythmia with narrow ventricular EGM correlated to narrow QRS complex Differentiation of narrow complex SVT from VT Limited specificity with BBB; may prevent therapy for narrow complex VT
  61. 61. Differentiation of SVT from VT parameter What It does Potentially useful For Potential problem Ventricular electrogram morphology Suppressed therapy for tachyarrhythmia with ventricular EGM morphology similar to that in sinus rhythm D/D SVT from VT Limited specificity with BBB Atrial to ventricular ratio Compare atrial to ventricular rate Atrial fibrillation Atrial undersensing can result in false diagnosis of VT
  62. 62. SVT Discriminators • Distinguishes SVTs by analyzing P and R-wave: –Rate –Regularity –AV Association PR Logic™ – Pattern
  63. 63. SVT Discriminators • Based on the premise that AF conducts irregularly to the ventricles (and VT is a stable, regular rhythm) • Discriminates regular from irregular intervals within a detect zone Stability
  64. 64. SVT Discriminators UnstableVaries >50 ms from previous 3 Stability = 50 ms Stability * in Medtronic devices
  65. 65. SVT Discriminators • Based on the premise that most VTs are characterized by a sudden onset •Evaluates the acceleration of the ventricular rate •Discriminates between: –Gradual rate increase –Abrupt rate increase •Determines VT present if rate increase is abrupt Onset
  66. 66. SVT Discriminators • Onset Percentage = 81% 530ms X 81% = 430ms 430ms  460ms = Onset Not Met Onset * in Medtronic devices
  67. 67. SVT Discriminators • Measures and stores the QRS characteristics of a normal sinus beat • Identifies SVT vs. VT based on the QRS changes that occur in most VTs SINUS RHYTHM VT Waveform Morphology
  68. 68. SVT Discriminators • Identifies start and end points of a sensed QRS complex • Uses 2 parameters to measures QRS: –Slew Width –Slew Threshold EGM Width
  69. 69. SVT Discriminators EGM Width
  70. 70. SVT Discriminators • Records and stores a template of a normal QRS wave •Compares stored template with a QRS occurring within the detection zone •Withholds detection if 3 of last 8 QRS complexes match the stored template – Detects VT/FVT/VF if 6 out of 8 do not match •Applies to initial detection only Wavelet
  71. 71. SVT Discriminators • Template % difference compared against: Match Threshold Value Wavelet
  72. 72. Refractory and Blanking Periods • Pacemaker sensing occurs when a signal is large enough to cross the sensing threshold 1.25 mV Sensitivity Time 5.0 mV 2.5 mV 1.25 mV Sensing does not tells us anything about the origin or morphology of the sensed event, only its “size.”
  73. 73. In DDD & VDD modes the pacemaker will “track” the atrium AS VP Tracking = Pacing the ventricle after an atrial intrinsic event Maintains AV Synchrony Want to limit how fast we pace Upper Tracking Rate
  74. 74. DDDR 60 / 120 A-A = 500 ms Upper Activity Rate Limit Lower Rate Limit Upper Sensor Rate • Sensor rate drives the atrial rate up • In rate responsive, dual chamber modes, the Upper Activity (Sensor) Rate provides the limit for sensor-driven atrial pacing PAV PAV 1000 ms 500 ms
  75. 75. Post Shock Pacing

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