1. PACEMAKER BASICS
Frijo jose a

2. Electrode on the tip of a pacing lead Anode: positive
Cathode: negative
Electrode on the tip of a pacing lead
Anode: positive
The “ring” electrode on a bipolar lead
The PG case on a unipolar system
Anode
Cathode

3. Implantable Pacemaker Circuit
Pulse generator (PG):
Battery
Circuitry
Connector(s)
Leads
Cathode
Anode
Body tissue
Lead
IPG
Anode
Cathode

4. The Pulse Generator Battery - provide energy
Circuitry - controls pacemaker operations
Connector- join the PG to the lead(s)
Connector Block
Circuitry
Battery

5. Lead Characterization
Position within the heart
Endocardial/transvenous leads
Epicardial leads
Fixation mechanism
Active/Screw-in
Passive/Tined
Shape
Straight
J-shaped used in the atrium
Polarity
Unipolar
Bipolar
Insulator
Silicone
Polyurethane

6. Endocardial Passive Fixation Leads
The tines become lodged in the trabeculae, a fibrous meshwork, of the heart
Tines

7. Transvenous Active Fixation Leads
The helix, or screw, extends into the endocardial tissue
Allows for lead positioning anywhere in the heart’s chamber
The helix is extended using an included tool

8. Epicardial Leads Leads applied directly to the surface of the heart
Fixation mechanisms include:
Epicardial stab-in
Myocardial screw-in
Suture-on
Applied via sternotomy or laproscopy

9. Lead Polarity Unipolar leads Bipolar leads
Smaller diameter lead body than bipolar leads
Usually larger pacing artifacts on ECG
Bipolar leads
Usually less susceptible to oversensing of non-cardiac signals
Unipolar lead
To tip (cathode)
Bipolar coaxial lead

10. Unipolar Pacing System
Lead has only one electrode –cathode – at the tip
PG can - anode
When pacing, the impulse:
Flows through the tip electrode (cathode)
Stimulates the heart
Returns through body fluid and tissue to PG can (anode)
Anode +
more interference (myopotentials)
Big spike on ECG
Pectoral (pocket) stimulation possible
Cathode -

11. Bipolar Pacing System The lead has both an anode and cathode
The pacing impulse:
Flows through the tip electrode located at the end of the lead wire
Stimulates the heart
Returns to the ring electrode, the anode, above the lead tip
Anode +
Cathode -
Anode
less interference
Spike difficult to see on ECG
No pectoral (pocket) stimulation
Cathode

12. STIMULATION THRESHOLD
The minimum stimulus intensity & duration necessary to reliably initiate a propagated depolarising wavefront from an electrode
For a pacing stimulus to “capture”, the stimulus must exceed a critical amplitude & must be applied for a sufficient duration
Stimulus amplitude & duration interact- minimal amplitude required to capture depends on the pulse duration

13. Strength–Duration Relation
Stimulus amplitude for endocardial stimulation has an exponential relation to duration of the pulse- rapidly rising strength–duration curve at pulse durations <0.25 ms and a relatively flat curve at pulse durations > 1.0 ms

14. Chronaxie pulse duration ~ point of min threshold energy on strength–duration curve
With pulse durations > chronaxie- relatively little ↓ in threshold V
Wider pulse dur→wasting of energy without providing a substantial ↑ in safety margin
When threshold determined by ↓ amplitude, stimulus V set twice the threshold value
PG that determine threshold by automatically ↓pulse duration-at least 3times threshold
Wedensky effect

15. Hyperacute phase of threshold evolution- active fixation electrodes may produce,immediately following implantation,an ↑ stimulation threshold that ↓over the next min- transient high threshold – a/c injury at myocardial–electrode interface

17. Proper programming of the stimulus amplitude
The strength–duration relation must be appreciated
The safety margin that is chosen for a particular pt must be based on the degree of pacemaker dependency
An appreciation of the effect of stimulus amplitude & duration on battery longevity
The overall metabolic & pharmacologic history of the pt must be considered
Pacing threshold varies inversely with surface area of the stimulating electrode

18. Strength–Interval Relation
The stimulation threshold is influenced by the coupling interval of electrical stimuli and frequency of stimulation
ICD- greater stimulus intensity during ATP than during antibradycardia pacing

19. (Ztotal) = Zc Ze Zp Zp - related to movmnt of charged ionmyo toward the s in cathode Zp -directly related to pulse duration & can be ↓ by use of relatively ↓ pulse durations Polarization is inversely related to SA of electrode- to ↓ Zp but ↑ Ze, SA of electrode can be made large but radius small by use of a porous coating

20. Afterpotential of opposite charge is induced in the myocardium at the interface of the stimulating electrode

21. The slope of intrinsic deflectn (dV/dt) expressed in V/s -referred to as slew rate For an EKG to be sensed, the amplitude & slew rate must exceed the sensing threshold

22. For a battery,the decay characteristics should be predictable
For a battery,the decay characteristics should be predictable. The ideal battery should have a predictable fall in V near the end of life, yet provide sufficient service life after initial voltage decay to allow time for the elective replacement indicator to be detected and for replacement to be performed

23. RATE-ADAPTIVE SENSORS
Activity Sensors and Accelerometers
Minute Ventilation Sensors

26. P- Native atrial depolarization
A- Atrial paced event
R- Native ventricular depolarization
V- Ventricular paced event
AV- Sequential pacing in the atrium and ventricle
AVI- Programmed AV pacing interval
AR- Atrial paced event foll by intrinsic ventricular
ARP- Atrial refractory period
PV- Native atrial foll by paced ventricular, P-synchronous
AEI- Interval from a ventricular sensed/paced to atrial paced event, the VA interval

27. NASPE/ BPEG Generic (NBG) Pacemaker Code
I. Chamber II. Chamber III. Response to IV. Programmability V. Antitachy
Paced Sensed Sensing Rate Modulation arrhythmia funct.
O= none O= none O= none O= none O= none
A=atrium A= atrium T= triggered P= simple P= pacing
V= ventricle V= ventricle I= inhibited M= multi S= shock
D= dual D= dual D= dual C= communication D= dual
(A+V) (A+V) (T+I) R= Rate Modulation
Manufacturers’ Designation only:
S= single S= single
(A or V) (A or V)

28. PACING MODES

29. AOO & VOO By application of magnet
Useful in diagnosing pacemaker dysfunction
During surgery to prevent interference from electrocautery

30. Ventricular asynchronous (VOO) pacing
Neither sensing nor mode of response
Irrespective of any other events, V pacing artifacts occur at programmed rate. Timing cycle cannot be reset by any intrinsic event

31. Atrial asynchronous (AOO) AV sequential asynchronous (DOO)
AVI & VAI or AEI are both fixed- intervals never change, as is insensitive to any atrial or ventricular activity, and timers never reset

32. Ventricular demand inhibited (VVI)
Sensing on V channel- output inhibited by sensed V event
Refractory after V/R- VRP- any V event in VRP-not sensed & doesn’t reset V timer
LRL

34. VVI MODE If the intervals are equal: No hysteresis
Automatic interval starts from a paced complex (to the next paced complex)
Escape interval starts from a sensed complex (to the next paced complex)
Automatic Interval
If the intervals are equal:
No hysteresis
If the escape interval > automatic interval:
Hysteresis
Escape Interval

35. VVI MODE (with hysteresis)
1000 ms
850 ms
Escape interval = 1000 ms (60 ppm)
Automatic interval = 850 ms (70 ppm)

36. AAI Useful for SSS with N- AV conduction
Should be capable of 1:1 AV to rates b/m
Atrial tachyarrhythmias should not be present
Atria should not be “silent”
If no A activity, atria paced at LOWER RATE limit (LR)
If A activity occurs before LR,- “resetting”
An A activity too early may not cause depolarisation & better not sensed- ARP
Caution- far-field sensing of V activity

37. Atrial inhibited (AAI) pacing

38. Single-Chamber Triggered-Mode
Output pulse every time a native event sensed
↑current drain
Deforms native signal
Prevent inappropriate inhibition from oversensing when pt does not have a stable native escape rhythm
Can be used for noninvasive EPS,with already implanted PPI tracking chest wall stimuli created by a programmable stimulator

39. Single-Chamber Rate-Modulated Pacing

40. AV sequential-V Inhibited Pacing (DVI)
PPI is inhibited & reset by sensed V activity but ignores all intrinsic A complexes
Native R during AVI sensed – V output inhibited & AEI reset
For both A&V stimuli to be inhibited, sensed R must occur during AEI

41. Modified or partially committed version-physiologic AVI

42. AV Sequential, Non–P-Synchronous Pacing with D-Chamber Sensing (DDI)
AAI + VVI
Difference btw DVI & DDI- DDI incorporates A sensing as well as V sensing- prevents competitive A pacing
Mode of response is inhibition only- no tracking of P waves - paced V rate cannot be > programmed LRL
Goes by LR for each
Timing cycles- LRL, AVI, PVARP & VRP

44. A Synchronous (P-Tracking) Pacing (VDD)
VAT + VVI
Timing cycle- LRL,AVI,PVARP,VRP,& URL
Concept of AV interval (AVI)
A sensed atrial event initiates AVI
Goes by LR
If no A event occurs, PPI escapes with a V pace at LRL- VVI
AV block with intact sinus node function (esp useful in congenital AV block)

46. DDD VAT + AAI + VVI AV interval & VA interval
VA interval replaces the LR
Concept of PVARP (to prevent endless loop or PMT)
Indications
1. The combination of AV block and SSS
2. Patients with LV dysfunction & LV hypertrophy who need coordination of atrial & ventricular contractions to maintain adequate CO

47. DDD

48. DDD Examples The Four Faces of DDD
Atrial and ventricular pacing
Atrial pace re-starts the lower rate timer and triggers an AV delay timer (PAV)
The PAV expires without being inhibited by a ventricular sense, resulting in a ventricular pace A P V

49. DDD Examples The Four Faces of DDD
Atrial pacing and ventricular sensing
Atrial pace restarts the lower rate timer and triggers an AV delay timer (PAV)
Before the PAV can expire, it is inhibited by an intrinsic ventricular event (R-wave) A P V S

50. DDD Examples The Four Faces of DDD
Atrial sensing, ventricular pacing
The intrinsic atrial event (P-wave) inhibits the lower rate timer and triggers an AV delay timer (SAV)
The SAV expires without being inhibited by an intrinsic ventricular event, resulting in a ventricular pace A S V P

51. DDD Examples The Four Faces of DDD
Atrial and ventricular sensing
The intrinsic atrial event (P-wave) inhibits the lower rate timer and triggers an AV delay timer (SAV)
Before the SAV can expire, it is inhibited by an intrinsic ventricular event (R-wave) A S V

52. Dual Response to Sensing DDD
The pacemaker can:
Inhibit and trigger
A P-wave inhibits atrial pacing and triggers an SAV interval
An atrial pace triggers a PAV interval
An R-wave inhibits ventricular pacing

54. Single-Chamber Timing

55. Single Chamber Timing Terminology
Lower rate
Refractory period
Blanking period
Upper rate

56. Lower Rate Interval Defines the lowest rate the pacemaker will paceVP
VVI / 60

57. Refractory Period Interval initiated by a paced or sensed event
Designed to prevent inhibition by cardiac or non-cardiac events
Lower Rate Interval VP
VVI / 60
Refractory Period

58. Blanking Period The first portion of the refractory period
Pacemaker is “blind” to any activity
Designed to prevent oversensing pacing stimulus
Lower Rate Interval VP
VVI / 60
Blanking Period
Refractory Period

59. Upper Sensor Rate Interval
Defines the shortest interval (highest rate) the pacemaker can pace as dictated by the sensor (AAIR, VVIR modes)
Lower Rate Interval
Upper Sensor Rate Interval VP
VVIR / 60 / 120
Blanking Period
Refractory Period

60. Lower Rate Interval-60 ppm
Hysteresis
Allows the rate to fall below the programmed lower rate following an intrinsic beat
Lower Rate Interval-60 ppm
Hysteresis Rate-50 ppm VP VP VS VP

61. Dual Chamber Timing Parameters
Lower rate
AV and VA intervals
Upper rate intervals
Refractory periods
Blanking periods

62. Lower Rate
The lowest rate the pacemaker will pace the atrium in the absence of intrinsic atrial events
Lower Rate Interval AP AP VP VP
DDD 60 / 120

63. AV Intervals
Initiated by a paced or non-refractory sensed atrial event
Separately programmable AV intervals – SAV /PAV
Lower Rate Interval
PAV
SAV
200 ms
170 ms AP VP AS
DDD 60 / 120

64. Atrial Escape Interval (V-A Interval)
The interval initiated by a paced or sensed ventricular event to the next atrial event
Lower Rate Interval
200 ms
800 ms
AV Interval
VA Interval AP VP
DDD 60 / 120
PAV 200 ms; V-A 800 ms

65. Upper Activity (Sensor) Rate
In rate responsive modes, the Upper Activity Rate provides the limit for sensor-indicated pacing
Lower Rate Limit
Upper Activity Rate Limit
PAV
V-A
PAV
V-A
DDDR 60 / 120
A-A = 500 ms AP VP

66. DDDR 60 / 100 (upper tracking rate)
The maximum rate the ventricle can be paced in response to sensed atrial events {
Lower Rate Interval
Upper Tracking Rate Limit
SAV VA
SAV VA AS VP
DDDR 60 / 100 (upper tracking rate)
Sinus rate: 100 bpm

69. 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 AP
A-V Interval
(Atrial Refractory)
Post Ventricular Atrial Refractory Period (PVARP) VP
Ventricular Refractory Period (VRP)

70. Blanking Periods
First portion of the refractory period-sensing is disabled AP AP VP
Atrial Blanking (Nonprogrammable)
Post Ventricular Atrial Blanking (PVAB)
Ventricular Blanking
(Nonprogrammable)
Post Atrial Ventricular Blanking

71. Dual Chamber Timing Atrial Pace (AP) - Ventricular Pace (VP) example
DDD 60
A-A interval
VRP
ARP
PVARP
PVAB
PAV
V-A interval

72. Atrioventricular Interval

76. thanks