1. Modes of Pacing Seoul National University Hospital
Department of Thoracic & Cardiovascular Surgery

2. Electrophysiology of Pacing
Stimulation & depolarization of myocardial tissue
Sensing of intramyocardial electrical activity
Current pacemaker technology
Pulse generator

3. Stimulation & Depolarization of Myocardial Tissue
The myocardium must be excitable
The stimulus current density (current per unit cross-sectional area) must be sufficiently high & of sufficient duration to depolarize a group of cells that is large enough to initiate impulse propagation in the myocardium
The pacemaker-generated impulse then relies on the intrinsic properties of cardiac specialized conduction & myocardial tissue for depolarization of the entire heart

4. Factors affecting Sensing
Sensing is the detection of real or spontaneous cardiac depolarization
Electrode size
Configuration of electrode (unipolar, bipolar)
Position of the lead tip within the heart

5. Pacing Lead Technology
Attachment of electrode
Active fixation
Passive fixation
1. Chronic ventricular pacing thresholds
tend to be lower with passive lead, in part
because of tissue injury with active fixation
2. Sensing characteristics are similar between
active & passive leads
3. Epicardial electrodes historically have poorer
performance over long term than endocardial
lead

6. Pulse Generator Power source Time circuitry Sensing circuitry
Output circuitry for channels connected to the electrodes
Transceiver for telemetric communication with programming device

7. Single Chamber Pacemaker
AOO
AAI
AAT
VOO
VVI
VVT

8. Single Chamber Pacemaker
AAIR
VVIR

9. Single Chamber Pacemaker
VVI I *

10. Intrinsic P and R waves

11. Atrial Sensing / Inhibition

12. Ventricular Sensing / Inhibition

13. Pacing Interval / Pacing Rate
The rate at which the pacemaker will pace if the patient does not have their own rhythm
Expressed in either PPM or ms

14. Rate Conversion Conversion Pacing rate in PPM divided into 60,000 = ms
60,000 / 60 PPM = 1000 ms
Interval in ms divided into 60,000 = PPM
60,000 / 1000 ms = 60 PPM

15. Ventricular Sensing / Inhibition
pacing interval

16. Capture
Definition The depolarization and resultant contraction of the atria or ventricles in response to a pacemaker stimulus.

17. Threshold Stimulation Threshold Definition :
The minimum amount of electrical energy that consistently produces a cardiac depolarization

18. Atrial Capture
Pacemaker Stimulus
Atrial Capture

19. Ventricular Capture Ventricular Capture (paced ventricular
beats look like PVC’s or LBBB)

20. Refractory Period
Refractory Period

21. Alert Period
Definition The portion of timing cycle where the device senses electrical activity (e.g. cardiac) & responds in a preset or programmed manner

22. Alert Period
Refractory Period
Alert Period

23. Dual Chamber Pacemaker
VAT
VDD
DOO
DVI
DDI
DDD

24. Dual Chamber Pacemaker
DDD
T / I * I

25. Atrial & Ventricular Pacing

26. Sense in Atrium & Pace in Ventricle

27. Pace & Sense in Atrium & Pace in Ventricle

28. Pace Atrium & Sense Ventricle

29. Pace and Sense in Atrium Sense in Ventricle

30. AV / PV Delay
AV Delay
PV Delay

31. Post Ventricular Atrial Refractory Period (PVARP)
Definition Timeframe the atrial channel is refractory, initiated when there is either a ventricular pacer spike or sensed R-wave.
PVARP

32. Atrial Alert Period
Definition Timeframe after PVARP when the sense amplifier is open and can see P-waves

33. Atrial Alert Period
Alert Period
PVARP
AV Delay
PV Delay

34. Ventricular Refractory Period

35. Ventricular Alert Period
Definition Timeframe after the ventricular refractory period that the sense amplifier is open looking for R-waves

36. Ventricular Alert Period
Ventricular Refractory Period
Ventricular Alert Period

37. Dual Chamber Pacing Minimum Rate or Base Rate
Lowest rate that the pacemaker will pace in the Atrium
Maximum length of time the Pacemaker will wait for intrinsic activity

38. Dual Chamber Pacing
Minimum Rate

39. Dual Chamber Pacing Maximum Rate / Maximum Tracking Rate
The fastest rate that the Ventricular channel can track intrinsic P-waves

40. Maximum Tracking Rate

41. Pacemaker Follow-up Aim Interval
Verify appropriate pacemaker operation
Optimize pacemaker functions
Interval
Immediate and POD # 1 day
Postoperative 3, 6, 12 months

42. Pediatric Aspects of Cardiac Pacing
Ventricular epicardial leads
Thoracotomy approach
Transdiaphragmatic approach
Subcostal or subxiphoid incision
Atrial epicardial leads
Base of left atrial appendage
Transvenous leads
All the leads have the problem with child growth and results in high threshold, exit block, lead fracture.
Even when a loop of lead was left in the pericardium, adhesions frequently formed that prevented unwinding of the loop.

43. Interrogation

44. Assess Current Pacemaker Function
Compare the surface ECG to markers to determine appropriate pacing (capture) & sensing

45. Measured Data Provides information on:
-Magnet Information, -Lead Status, -Battery Status

46. Diagnostics

47. Pacemaker Testing Sensing and Capture testing
should be performed to insure
adequate safety margins are
programmed

48. Ventricular Threshold Test
Sensing and Capture testing should be performed to insure adequate safety margins are programmed

49. Loss of Capture Definition:
The emitted pacemaker stimulus does not cause depolarization and resultant cardiac contraction

50. Ventricular Loss of Capture
Programmed Rate
Programmed Rate

51. Problem Solving Loss of Capture Causes Dislodged Lead Insulation Break
Program Voltage higher
Program Pulse Width higher
Reposition pacing electrode

52. Sensing Threshold
The sensitivity number is increased until loss of sensing is seen
Then the sensitivity number is decreased until sensing is regained
This is the Sensing Threshold

53. Ventricular Sensitivity Test

54. Oversensing Definition :
The sensing of events other than P or R-waves by the pacemaker circuitry

55. Ventricular Oversensing
Pacing
interval
Pacing
interval
Pacing
interval
Pacing
interval
Pacing
interval

56. Causes of Oversensing Insulation Break Intermittent Lead Fracture
Myopotentials
EMI
Problem Solving
Program sensitivity to a higher number
Program the refractory period longer

57. Undersensing Definition :
Failure of the pacemaker circuitry to sense intrinsic P- or R-waves

58. Ventricular Undersensing
non-sensed R-waves

59. Causes of Undersensing Dislodged Lead Insulation Break Problem Solving Program the sensitivity to a lower number

60. Testing of Chronic Pacing System
Current Voltage Resistance
Threshold Threshold
Dislodgement of electrode from endocardium H H N
Perforation H H N
Exit block (fibrosis around electrode tip) H H N
Pulse generator malfunction N N N
Lead/connector abnormality N N N
Battery depletion N N N
Partial lead fracture L to N H H
F F
Complete lead fracture N H H
Lead insulation fracture H H L
H; high, N; normal, L; low. F; fluctuating

61. Follow-up Check Interrogate Measure Impedance Check Diagnostics
Check Sensing
Measure Threshold