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BASICS OF PACEMAKER DN. HISTORY 1958 – Senning and Elmqvist – Asynchronous (VVI) pacemaker implanted by thoracotomy and functioned for 3 hours – Arne.

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Presentation on theme: "BASICS OF PACEMAKER DN. HISTORY 1958 – Senning and Elmqvist – Asynchronous (VVI) pacemaker implanted by thoracotomy and functioned for 3 hours – Arne."— Presentation transcript:

1 BASICS OF PACEMAKER DN

2 HISTORY 1958 – Senning and Elmqvist – Asynchronous (VVI) pacemaker implanted by thoracotomy and functioned for 3 hours – Arne Larsson First pacemaker patient Used 23 pulse generators and 5 electrode systems Died 2001 at age 86 of cancer 1960 – First atrial triggered pacemaker 1964 – First on demand pacemaker (DVI) 1977 – First atrial and ventricular demand pacing (DDD) 1981 – Rate responsive pacing by QT interval, respiration, and movement 1994 – Cardiac resynchronization pacing

3 What is a Pacemaker? A Pacemaker System consists of a Pulse Generator plus Lead (s)

4 S Pulse generator- power source or battery Leads Cathode (negative electrode) Anode (positive electrode) Body tissue IPG Lead Anode Cathode Implantable Pacemaker Systems Contain the Following Components:

5 Contains a battery that provides the energy for sending electrical impulses to the heart Houses the circuitry that controls pacemaker operations Circuitry Battery The Pulse Generator

6 Casing (can) – Titanium (biocompatible, lightweight, stronger than steel) Connector (header) – Leads plug into ports in the clear epoxy header Components – Diodes, resistors, oscillator, microchips Battery – The largest single component inside the pulse generator – Lithium iodide

7 Battery Connector Hybrid Telemetry antenna Output capacitors Reed (Magnet) switch Clock Defibrillation protection Atrial connector Ventricular connector Resistors Anatomy of a Pacemaker

8 General Characteristics of Pacemaker Batteries Hermeticity, as defined by the pacing industry, is an extremely low rate of helium gas leakage from the sealed pacemaker container low rate of self-discharge lithium iodine -a long shelf life and high energy density DDD drains a battery more rapidly

9 Longevity in single chamber pacemaker is 7 to 12 years. For dual chamber longevity is 6 to 10 years. Most pacemakers generate 2.8 v in the beginning of life which becomes 2.1 to 2.4 v towards end of life. Power source 9

10 halving of output voltage increases the longevity of battery by almost twice the number of years.

11 Simplified model of a lithium iodine battery The open-circuit voltage of 2.8 V is characteristic of lithium iodine chemistries. The series resistance increases from 100 W at beginning of battery life (BOL) to more than 10,000 W at end of life (EOL).

12 Deliver electrical impulses from the pulse generator to the heart Sense cardiac depolarisation Lead Leads

13 ConductorTip ElectrodeInsulationConnector Pin Pacing Lead Components Conductor Connector Pin Insulation Electrode

14 Lead Characterization Position within the heart – Endocardial or 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

15 Conductor Connector Pin Insulation Electrode Lead components

16 Transvenous Leads - Fixation Mechanisms

17 Fixation mechanisms of the Electrode Passive fixation Wingtips Active fixation Screw Active fixation Tines

18 Passive fixation – The tines become lodged in the trabeculae

19 Active Fixation – The helix (or screw) extends into the endocardial tissue – Allows for lead positioning anywhere in the heart’s chamber

20 Myocardial and Epicardial Leads Leads applied directly to the heart – Fixation mechanisms include: Epicardial stab-in Myocardial screw-in Suture-on

21 21

22 Active FixationPassive Fixation AdvantagesEasy fixation Easy to reposition Lower rate of dislodgement Removability Less expensive & simple Minimal trauma to patient Lower thresholds DisadvantagesMore expensive >Complicated implantation Higher rate of dislodgement (>a/c) Difficult to remove chronic lead

23 Cathode:-An electrode that is in contact with the heart Negatively charged Anode:-receives the electrical impulse after depolarization of cardiac tissue Positively charged when electrical current is flowing Cathode Anode

24 Flows through the tip electrode (cathode) Stimulates the heart Returns through body fluid and tissue to the PG (anode) A Unipolar Pacing System Contains a lead with an electrode in the heart Cathode Anode - +

25 Flows through the tip electrode located at the end of the lead wire Stimulates the heart Returns to the ring electrode above the lead tip A Bipolar Pacing System Contains a lead with 2 electrodes in the heart Cathode

26 Unipolar leads Unipolar leads have a smaller diameter than bipolar leads Unipolar leads exhibit larger pacing artifacts on the surface ECG One electrode on the tip & one conductor coil Conductor coil may consist of multiple strands - (multifilar leads)

27 Bipolar leads Bipolar leads are less susceptible to oversensing noncardiac signals (myopotentials and EMI) Coaxial Lead Design Circuit is tip electrode to ring electrode Two conductor coils (one inside the other) Inner layer of insulation Bipolar leads are typically thicker than unipolar leads

28 UnipolarBipolar AdvantagesSmaller diameter Easier to implant Large spike No pocket stimulation Less susceptible to EMI Programming flexibility DisadvantagesPocket stimulation Far-field oversensing No programming flexibility Larger diameter Stiffer lead body Small spike Higher impedance Voltage threshold is 30% higher

29 Unipolar vs bipolar – Size – Higher impedance for bipolar – Same current threshold – Voltage threshold is 30% higher for bipolar – Unipolar may oversense and bipolar may undersense – Skeletal muscle stimulation – Stimulus Artifact Amplitude – observer and ICD implications Best distance is 1 cm for bipolar. Smaller tip- lower threshold for pacing, offset later by polarisation. Ideal impedance is 400 to 1,200 ohms.

30

31 Electrodes Leads have 1/> electrically active surfaces referred to as the electrodes Deliver an electrical stimulus, detect intrinsic cardiac electrical activity, or both Electrode performance can be affected by – Materials – Polarization – Impedance – Pacing thresholds – Steroids

32 Electrode Materials The ideal material for an electrode – Porous (allows tissue ingrowth) – Should not corrode or degrade – Small in size but have large surface area – Common materials Platinum and alloys (titanium-coated platinum iridium) Vitreous carbon (pyrolytic carbon) Stainless steel alloys such as Elgiloy

33 Voltage Voltage is the force that causes electrons to move through a circuit In a pacing system, voltage is: – Measured in volts – Represented by the letter “V” – Provided by the pacemaker battery – Referred to as amplitude

34 Current The flow of electrons in a completed circuit In a pacing system, current is: – Measured in mA (milliamps) – Represented by the letter “I” – Determined by the amount of electrons that move through a circuit

35 Constant-Voltage and Constant-Current Pacing Most permanent pacemakers are constant- voltage pacemakers Voltage and Current Threshold Voltage threshold is the most commonly used measurement of pacing threshold

36 Pacing Thresholds Defined as the minimum amount of electrical energy required to consistently cause a cardiac depolarization “Consistently” refers to at least ‘5’ consecutive beats Low thresholds require less battery energy CaptureNon-Capture

37 The Strength-Duration Curve The strength-duration curve illustrates the relationship of amplitude and pulse width – Values on or above the curve will result in capture Duration Pulse Width (ms) Stimulation Threshold (Volts) Capture

38 Strength-Duration Curve

39 Rheobase- (the lowest point on the curve) by definition is the lowest voltage that results in myocardial depolarization at infinitely long pulse duration Chronaxie(pulse duration time ) by definition, the chronaxie is the threshold pulse duration at twice the rheobase voltage

40 typical pulse width setting is 0.5 msec chronaxie point is two times the rheobase a moderately high impedance with a good threshold leads to an ideal situation in which the heart is easily paced with a minimum number of electrons (i.e., less battery drain). anxiety related to pacemaker insertion can increase levels of circulating catecholamines, causing lower thresholds lowest threshold (acute threshold) at the time of implantation 2 to 6 weeks, the threshold rises to its highest level -edema and inflammation Then falls- fibrous tissue- electric charge is now less dispersed- impedance remains unchanged.

41 Lessons from SDC The ideal pulse duration should be greater than the chronaxie time Cannot overcome high threshold exit block by increasing the pulse duration, If the voltage output remains less than the rheobase Energy (μJ) = Voltage (V) × Current (mA) × Pulse Duration (PD in ms). Charge (μC) = Current (mA) × Pulse Duration (ms).

42 At very low pulse width thresholds, the charge is low, but the energy requirements are high because of elevated current and voltage stimulation thresholds. At pulse durations of 0.4–0.6 ms, all threshold parameters - ideal At high pulse durations, the voltage and current requirements may be low, but the energy and charge values are unacceptable

43 - Safety margins -When a threshold is determined by decrementing the pulse width at a fixed voltage At a given voltage where the pulse width value is <.30 ms: Tripling the pulse width will provide a two-time voltage safety margin. – Daily fluctuations in threshold that can occur due to eating, sleeping, exercise, or other factors - a/c pacing system - higher safety margin, due to the lead maturation process- occur within the first 6-8 weeks following implant.

44 Changes in stimulation threshold (voltage or current) following implantation of a standard nonsteroid-eluting electrode

45 Impedance The opposition to current flow In a pacing system, impedance is – Measured in ohms – Represented by the letter “R” (  for numerical values) The measurement of the sum of all resistance to the flow of current Resistance is a term used to refer to simple electric circuits without capacitors and with constant voltage and current Impedance is a term used to describe more complex circuits with capacitors and with varying voltage and current

46 Impedance Pacing lead impedance typically stated in broad ranges, i.e. 300 to 1500 Ω Factors that can influence impedance – Resistance of the conductor coils – Tissue between anode and cathode – The electrode/myocardial interface – Size of the electrode’s surface area – Size and shape of the tip electrode

47 Ohm’s Law is a Fundamental Principle of Pacing That:VI R V = I X R I = V / R R = V / I Describes the relationship between voltage, current, and resistance x

48 If you reduce the voltage by half, the current is also cut in half If you reduce the impedance by half, the current doubles If the impedance increases, the current decreases When Using Ohm’s Law You Will Find That:

49 Resistance and Current Flow “Normal” resistance “Low” resistance “High” resistance Low current flow High current flow

50 Voltage and Current Flow Spigot (voltage) turned up (high current drain) Spigot (voltage) turned low (low current drain)

51 Impedance and Electrodes Large electrode tip – Threshold ↑ – Impedance ↓ – Polarization ↓ Small electrode tip – Threshold ↓ – Impedance ↑ – Polarization ↑

52 Polarization After an output pulse, positively charged particles gather near the electrode. The amount of positive charge is – Directly proportional to pulse duration – Inversely proportional to the functional electrode size (i.e. smaller electrodes offer higher polarization) Polarization effect can represent 30–40% of the total pacing impedance As high as 70% for smooth surface, small surface area electrodes

53 Within the electrode, current flow is due to movement of electrons (e−). At the electrode–tissue interface, the current flow becomes ionic & (-) vely charged ions (Cl−, OH−) flow into the tissues toward the anode leaving behind oppositely charged particles attracted by the emerging electrons. It is this capacitance effect at the electrode tissue interface, that is the basis of polarization

54 Lead Maturation Process Fibrotic “capsule” develops around the electrode following lead implantation 3 phases 1.A/c phase, where thresholds immediately following implant are low 2.Peaking phase- thresholds rise and reach their highest point(1wk),followed by a ↓ in the threshold over the next 6 to 8 wks as the tissue reaction subsides 3.C/c phase- thresholds at a level higher than that at implantation but less than the peak threshold Trauma to cells surrounding the electrode→ edema and subsequent development of a fibrotic capsule. Inexcitable capsule ↓ the current at the electrode interface, requiring more energy to capture the heart.

55 Steroid Eluting Leads Steroid eluting leads reduce the inflammatory process and thus exhibit little to no acute stimulation threshold peaking and low chronic thresholds Porous, platinized tip for steroid elution Silicone rubber plug containing steroid Tines for stable fixation

56 Lead Maturation Process Effect of Steroid on Stimulation Thresholds Pulse Width = 0.5 msec 0 36 Implant Time (Weeks) Textured Metal Electrode Smooth Metal Electrode Steroid-Eluting Electrode Volts

57

58

59 Sensing Sensing is the ability of the pacemaker to detect an intrinsic depolarization – Pacemakers sense cardiac depolarization by measuring changes in electrical potential of myocardial cells between the anode and cathode

60 An Electrogram (EGM) is the Recording of Cardiac Waveforms Taken From Within the Heart Intrinsic deflection on an EGM occurs when a depolarization wave passes directly under the electrodes Two characteristics of the EGM are: – Signal amplitude(mv) – Slew rate(v/sec)

61 Intrinsic R wave Amplitude Typical intrinsic R wave amplitude measured from pacing leads in the Right Ventricle are more than 5 mV in amplitude Amplitude Intrinsic R wave in EGM The Intrinsic R wave amplitude is usually much greater than the T wave amplitude

62

63 Slew Rate of the EGM Signal Measures the Change in Voltage with Respect to the Change in Time The longer the signal takes to move from peak to peak: – The lower the slew rate – The flatter the signal Higher slew rates translate to greater sensing – Measured in volts per second Voltage Time Slope Slew rate= Change in voltage Time duration of voltage change Slew rate measurements at implant should exceed.5 volts per second for P waves;.75 volts per second for R wave measurements

64 Factors That May Affect Sensing Are: Lead polarity (unipolar vs. bipolar) Lead integrity – Insulation break – Wire fracture EMI – Electromagnetic Interference

65 Undersensing... Pacemaker does not “see” the intrinsic beat, and therefore does not respond appropriately Intrinsic beat not sensed Scheduled pace delivered VVI / 60

66 Oversensing An electrical signal other than the intended P or R wave is detected Marker channel shows intrinsic activity......though no activity is present VVI / 60

67 Signal Amplitude / Slew Rate Signal Pacemaker Implantation

68 Rate Programmability The pacemaker function most commonly programmed is rate

69 Pulse-Width Programmability

70 Voltage Programmability

71 Refractory Period Programmability

72 Hysteresis Programmability

73 NASPE/ BPEG Generic (NBG) Pacemaker Code I Chamber Paced II Chamber Sensed III Response to Sensing IV Programmable Functions/Rate Modulation V Antitachy Function(s) V: Ventricle T: Triggered P: Simple programmable P: Pace A: Atrium I: Inhibited M: Multi- programmable S: Shock D: Dual (A+V) D: Dual (T+I) C: Communicating D: Dual (P+S) O: None R: Rate modulating O: None S: Single (A or V) S: Single (A or V) O: None

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75 Pacemaker Timing Pacing Cycle : Time between two consecutive events in the ventricles (ventricular only pacing) or the atria (dual chamber pacing) Timing Interval : Any portion of the Pacing Cycle that is significant to pacemaker operation e.g. AV Interval, Ventricular Refractory period

76

77 Single-Chamber Timing

78 Single Chamber Timing Terminology Lower rate Refractory period Blanking period Upper rate

79 Lower Rate Interval VP VVI / 60 Defines the lowest rate the pacemaker will pace

80 Refractory Period Lower Rate Interval VP VVI / 60 Interval initiated by a paced or sensed event Designed to prevent inhibition by cardiac or non-cardiac events Events sensed in the refractory period do not affect the Lower Rate Interval but start their own Refractory Periods Refractory Period

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

82 Physiologic Classification of Sensors- rate adaptive Primary Physiologic factors that modulate sinus function Catecholamine level, Autonomic nervous system activity Secondary Physiologic parameters that are the consequence of exercise QT, respiratory rate Minute ventilation,temperature pH, stroke volume, Preejection interval, SV O2 Peak endocardial acceleration Tertiary External changes that result from exercise Vibration Acceleration

83 Upper Sensor Rate Interval Lower Rate Interval VP VVIR / 60 / 120 Defines the shortest interval (highest rate) the pacemaker can pace as dictated by the sensor (AAIR, VVIR modes) Limit at which sensor-driven pacing can occur Blanking Period Refractory Period Upper Sensor Rate Interval

84 VP VS VP Lower Rate Interval-60 ppm Hysteresis Allows the rate to fall below the programmed lower rate following an intrinsic beat lower rate limit is initiated by a paced event, while the hysteresis rate is initiated by a non-refractory sensed event. Hysteresis Rate-50 ppm

85 Noise Reversion VP SR Noise Sensed Lower Rate Interval VVI/60 Continuous refractory sensing will cause pacing at the lower rate

86 Modes-SINGLE CHAMBER

87 AOO & VOO-asynchronous modes By application of magnet Useful in diagnosing pacemaker dysfunction During surgery to prevent interference from electrocautery

88 VOO Mode Blanking Period VP Lower Rate Interval VOO / 60 Asynchronous pacing delivers output regardless of intrinsic activity

89 V VP VOO TIMING VP

90 VVI Mode Lower Rate Interval VP VS Blanking/Refractory VP { VVI / 60 Pacing inhibited with intrinsic activity

91 V VP VS VVI TIMING

92 VVIR VP Refractory/Blanking Lower Rate Upper Rate Interval (Maximum Sensor Rate) VVIR / 60/120 Rate Responsive Pacing at the Upper Sensor Rate Pacing at the sensor-indicated rate

93 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” Caution- far-field sensing of V activity

94 AAIR Lower Rate Interval AP Refractory/Blanking Upper Rate Interval (maximum sensor rate) AAIR / 60 / 120 (No Activity) Atrial-based pacing allows the normal A-V activation sequence to occur

95 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

96 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

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

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

99 AV Delay The AV delay in the pacemaker timing cycle is designed to simulate that natural pause between the atrial and ventricular events by mimicking the PR interval Benefits of a properly timed AV delay – Allows optimal time for ventricular filling, which may contribute to improved cardiac output – Allows sufficient time for proper mitral valve closure- minimize MR

100 AP VP AS VP PAV SAV 200 ms 170 ms Lower Rate Interval AV Intervals Initiated by a paced or non-refractory sensed atrial event – Separately programmable AV intervals – SAV /PAV Two things can happen with the AV delay – AV delay times out (and ventricular pacing spike is delivered) – AV delay is interrupted by a sensed ventricular event (and ventricular pacing spike is inhibited) DDD 60 / 120

101 Paced AV Delay The time period between the paced atrial event and the next paced ventricular event The pacemaker spike initiates the paced AV delay timing cycle Programmable value Sensed AV Delay The time period between the sensed atrial event and the next paced ventricular event The pacemaker has to sense the atrial event before the timing cycle is initiated— there is usually a slight time lag Program the sensed AV delay to a value slightly shorter than the paced AV delay (~ 25 ms)

102 Atrial Escape Interval (V-A Interval) Lower rate interval- AV interval =V-A interval The V-A interval is the longest period that may elapse after a ventricular event before the atrium must be paced in the absence of atrial activity. The V-A interval is also commonly referred to as the atrial escape interval

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

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

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

106 Post Ventricular Atrial Refractory Period (PVARP) 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 VP Ventricular Refractory Period (VRP) A-V Interval (Atrial Refractory)

107 Post-Ventricular Atrial Refractory Period PVARP is initiated by a ventricular event(sensed/paced), but it makes the atrial channel refractory PVARP is programmable (typical settings around ms) Benefits of PVARP – Prevents atrial channel from responding to premature atrial contractions, retrograde P-waves, and far-field ventricular signals – Can be programmed to help minimize risk of pacemaker-mediated tachycardias

108 PVARP and PVAB The PVAB is the post-ventricular atrial blanking period during which time no signals are “seen” by the pacemaker’s atrial channel It is followed by the PVARP, during which time the pacemaker might “see” and even count atrial events but will not respond to them PVAB-independently programmable – Typical value around 100 ms

109 PVAB and PVARP

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

111 Total Atrial Refractory Period (TARP) TARP is the timing cycle on the atrial channel during which the pacemaker will not respond to incoming signals TARP consists of the AV delay plus the PVARP TARP = AV delay + PVARP TARP is not programmable directly -can program the AV delay and PVARP and thus indirectly control TARP TARP is important for controlling upper-rate behavior of the pacemaker

112 PVARP Upper Tracking Rate Lower Rate Interval { No SAV started for events sensed in the TARP AS VP SAV = 200 ms PVARP = 300 ms Thus TARP = 500 ms (120 ppm) DDD LR = 60 ppm (1000 ms) UTR = 100 bpm (600 ms) SAV TARP PVARP Total Atrial Refractory Period (TARP) Sum of the AV Interval and PVARP defines the highest rate that the pacemaker will track atrial events before 2:1 block occurs SAV

113 Wenckebach Occurs when the intrinsic atrial rate lies between the UTR and the TARP rate Results in gradual prolonging of the AV interval until one atrial intrinsic event occurs during the TARP and is not tracked

114 PVARP Wenckebach Operation Upper Tracking Rate Lower Rate Interval { AS AR AP VP TARP SAV PAVPVARP SAV PVARP P Wave Blocked (unsensed or unused) Prolongs the SAV until upper rate limit expires – Produces gradual change in tracking rate ratio TARP

115 Wenckebach Operation DDD / 60 / 120 / 310

116 Fixed Block or 2:1 Block Occurs whenever the intrinsic atrial rate exceeds the TARP rate Every other atrial event falls in the TARP when the atrial rate exceeds the TARP rate Results in block of atrial intrinsic events in fixed ratios

117 Every other P wave falls into refractory and does not restart the timing interval Upper Tracking Limit Lower Rate Interval { { P Wave Blocked AS VP AR Sinus rate = 133 bpm (450 ms) PVARP = 300 ms SAV = 200 ms TARP=500 ms AVPVARP AVPVARP TARP 2:1 Block

118 DDD / 60 / 120 / 310

119 Summary-upper rate behaviours – 1:1 tracking occurs whenever the patient’s atrial rate is below the upper tracking rate limit – Wenckebach will occur when the atrial rate exceeds the upper tracking rate limit – Atrial rates greater than TARP cause 2:1 block

120 Ventricular Safety Pacing Crosstalk is the sensing of a pacing stimulus delivered in the opposite chamber, which results in undesirable pacemaker response, e.g., false inhibition Following an atrial paced event, a ventricular safety pace interval is initiated – If a ventricular sense occurs during the safety pace window, a pacing pulse is delivered at an abbreviated interval (110 ms) Post Atrial Ventricular Blanking PAV Interval Ventricular Safety Pace Window

121 Ventricular Safety Pace DDD 60 / 120

122 PVARP Ventricular Safety Pace AVPVARP AV 110 ms VS VPVP AP

123 VDD Mode Atrial Synchronous pacing or Atrial Tracking Mode A sensed intrinsic atrial event starts an SAV The Lower Rate Interval is measured between Vs to Vp or Vp to Vp If no atrial event occurs at the end of the Lower Rate Interval a Ventricular pace occurs Paces in the VVI mode in the absence of atrial sensing AV block with intact sinus node function (esp useful in congenital AV block)

124 VDD Upper Tracking Limit VDD LR = 60 ppm UTR = 120 ppm Spontaneous A activity = 700 ms (85 ppm) Lower Rate Interval { AS VP Provides atrial synchronous pacing – System utilizes a single lead

125 DDD Mode Chamber paced: Atrium & ventricle Chamber sensed: Atrium & ventricle Response to sensing: Triggered & inhibited – An atrial sense: Inhibits the next scheduled atrial pace Re-starts the lower rate timer Triggers an AV interval (called a Sensed AV Interval or SAV) – An atrial pace: Re-starts the lower rate timer Triggers an AV delay timer (the Paced AV or PAV) – A ventricular sense: Inhibits the next scheduled ventricular pace

126 Dual chamber timing AVI + PVARP = TARP PVARP Atrial Channel Ventricular Channel VRP VAI URI Atrial Escape Timing VAIAVI NOTES: LRI = VAI + AVI AVIPVARP A spontaneous ventricular contraction has shortened the AVI and therefore the TARP PVARP extension after a PVC AVI BL

127 The Four States of DDD Pacing

128 Rate (sinus driven) = 70 bpm / 857 ms Spontaneous conduction at 150 ms A-A = 857 ms AS VS AS VS V-A AV V-A Atrial Sense, Ventricular Sense (AS/VS) Four “Faces” of Dual Chamber Pacing

129 Rate = 60 bpm / 1000 ms A-A = 1000 ms AP VP AP VP V-A AV V-A AV Atrial Pace, Ventricular Pace (AP/VP) Four “Faces” of Dual Chamber Pacing

130 Rate = 60 ppm / 1000 ms A-A = 1000 ms AP VS AP VS V-A AV V-A AV Atrial Pace, Ventricular Sense (AP/VS) Four “Faces” of Dual Chamber Pacing

131 AS VP AS VP Rate (sinus driven) = 70 bpm / 857 ms A-A = 857 ms Atrial Sense, Ventricular Pace (AS/ VP) V-A AV V-A Four “Faces” of Dual Chamber Pacing

132 Mode Selection DDIR DDDR N VVI VVIR Are they chronic? Y YN DDD, VDD DDDR YN Is AV conduction intact? Is SA node function presently adequate? Symptomatic bradycardia Are atrial tachyarrhythmias present? Is SA node function presently adequate? Is AV conduction intact? Y Y N AAIR DDDR DDDR, DDIR NN (SSS) N

133 Optimal Pacing Mode (BPEG) Sinus Node Disease-AAI (R) AVB-DDD SND + AVB-DDDR + DDIR Chronic AF + AVB-VVI

134 Alternative Pacing Mode Sinus Node Disease-AAI AVB-VDD SND + AVB-DDD + DDI Chronic AF + AVB-VVI

135 Thank u

136 Mode Selection Decision Tree DDIR with SV PVARP DDDR with MS N VVI VVIR Are they chronic? Y YN DDD, VDD DDDR YN Is AV conduction intact? Is SA node function presently adequate? Symptomatic bradycardia Are atrial tachyarrhythmias present? Is SA node function presently adequate? Is AV conduction intact? Y Y N AAIR DDDR DDD, DDI with RDR NN (SSS) (CSS, VVS) N

137 Stuart Allen 06 Pacing Modes

138 Output circuit VVI AMP Ventricular Demand Programmed lower rate 50 mm/s VVI

139

140 Stuart Allen 06 Output circuit VVIR AMP Sensor Ventricular Demand Pacing Modesp Programmed lower rate 50 mm/s Sensor indicated rate

141 Stuart Allen 06 Output circuit AAI AMP Atrial Demand Programmed lower rate50 mm/s AAI

142 Stuart Allen 06 Pacing Modes - Summary Output circuit VAT AMP Atrial Synchronised Output circuit AAI AMP Atrial Demand Output circuit DVI AMP A-V Sequential Output circuit VDD AMP Atrial synchronised Ventricular Inhibited AMP Output circuit DDD AMP A-V Universal Output circuit Timing & Control AMP Output circuit VVI AMP Ventricular Demand


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