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. 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. 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. 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. 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. 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. PACING MODES
Pacing Modes

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. Knowledge Checkpoint
What is the rhythm? What type of device does this patient
need?

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. 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. 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. 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. Knowledge Checkpoint
What is the rhythm? What type of device does this patient
need?

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. AAI
• Paces in the atrium
• Timed from last P wave
Pacing Interval
A
P
A
P
Lower Rate Timer 1000 ms

17. Knowledge Checkpoint
What is the rhythm? What type of device does this patient
need?

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. 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. Knowledge Checkpoint
A
B
C
D
Label each EKG with the faces of pacing (AS-VS, AP-VS, AP-VP,
AS-VP).

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. 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. 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. Rate hysteresis

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. 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. AV hysteresis

28. Programmer

29. Programmer - PAV, SAV

30. Programmer - Mode Switch

31. ICD Function
What is the function of an ICD?
• Sense cardiac rhythms
• Detect arrhythmias
• Deliver therapy
• Pace when necessary

32. Typical Transvenous Lead

33. Transvenous Leads
Placement
Single Coil Dual Coil

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. 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. 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. 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. 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. 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. 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. Shock Reduction
• Anti-tachycardia pacing
• 延長VT/VF偵測
• 藥物

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. Anti-tachycardia pacing (ATP)

44. ATP的風險

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. Sensing
• Sensing is:
–The process of identifying cardiac depolarizations from an
intracardiac electrogram
Measured Peak-to-Peak
>5 mV for optimal sensing

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. Detection
Zone Classifications

49. ＩＣＤexample

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. Detection
Used for detection of VT
Consecutive Counter

52. Detection
NID = 12/16
Probabilistic Counter

53. • Can you identify the detect zones?
• Name the rate & duration for each
Detection
Detect Zones

54. Cardioversion
• Delivers shock on an R-wave
• Aborts if synchronization cannot be obtained due to
arrhythmia termination

55. Cardioversion

56. Defibrillation
Programming
*Medtronic Programming Screen

57. Major Challenges Faced
• Inappropriate therapies
• Unnecessary shocks
• Repetitive shocks
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.

60. 辛苦了
謝謝聆聽

61. 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

62. 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

64. SVT Discriminators
• Distinguishes SVTs by analyzing P and R-wave:
–Rate
–Regularity
–AV Association
PR Logic™
– Pattern

65. 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

66. SVT Discriminators
UnstableVaries >50 ms from previous 3
Stability = 50 ms
Stability
* in Medtronic devices

67. 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

68. SVT Discriminators
• Onset Percentage = 81%
530ms X 81% =
430ms
430ms  460ms = Onset Not Met
Onset
* in Medtronic devices

69. 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

70. SVT Discriminators
• Identifies start and end points of a sensed QRS
complex
• Uses 2 parameters to measures QRS:
–Slew Width
–Slew Threshold
EGM Width

71. SVT Discriminators
EGM Width

72. 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

73. SVT Discriminators
• Template
% difference compared against:
Match Threshold Value
Wavelet

74. 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.”

75. 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

76. 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

77. Post Shock Pacing