basics of pacemaker
DESCRIPTION
BASICS OF PACEMAKER. DN. HISTORY. 1958 – Senning and Elmqvist Asynchronous (VVI) pacemaker implanted by thoracotomy and functioned for 3 hours Arne Larsson First pacemaker patient - PowerPoint PPT PresentationTRANSCRIPT
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BASICS OF PACEMAKER
DN
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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
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What is a Pacemaker?What is a Pacemaker?
A Pacemaker System consists of a Pulse Generator plus Lead (s)
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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:Implantable Pacemaker Systems Contain the Following Components:
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• 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 GeneratorThe Pulse Generator
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Battery
Connector
Hybrid
Telemetry antenna
Output capacitors
Reed (Magnet) switch
Clock
Defibrillation protection
Atrial connector
Ventricular connector
Resistors
Anatomy of a PacemakerAnatomy of a Pacemaker
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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
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• 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
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• Deliver electrical impulses from the pulse generator to the heart
• Sense cardiac depolarisationLead
LeadsLeads
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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
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• Conductor • Connector Pin• Insulation• Electrode
Lead components
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Transvenous Leads - Fixation Mechanisms
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• Passive fixation
– The tines become lodged in the trabeculae
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• Active Fixation
– The helix (or screw) extends into the endocardial tissue
– Allows for lead positioning anywhere in the heart’s chamber
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Myocardial and Epicardial Leads
• Leads applied directly to the heart– Fixation mechanisms
include:• Epicardial stab-in• Myocardial screw-in• Suture-on
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Active Fixation Passive Fixation
Advantages Easy fixationEasy to repositionLower rate of dislodgementRemovability
Less expensive & simpleMinimal trauma to patientLower thresholds
Disadvantages More expensive>Complicated implantation
Higher rate of dislodgement (>a/c)Difficult to remove chronic lead
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• 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
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• 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
-
+
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Anode
• 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
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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)
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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
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Unipolar Bipolar
Advantages Smaller diameterEasier to implantLarge spike
No pocket stimulationLess susceptible to EMIProgramming flexibility
Disadvantages
Pocket stimulationFar-field oversensingNo programming flexibility
Larger diameterStiffer lead bodySmall spikeHigher impedance Voltage threshold is 30% higher
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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
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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
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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
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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
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• 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
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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
Capture Non-Capture
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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)
.50
1.0
1.5
2.0
.25S
tim
ula
tio
n T
hre
sho
ld (
Vo
lts)
0.5 1.0 1.5
Capture
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• 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
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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).
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• 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
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-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.
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Changes in stimulation threshold (voltage or current) following implantationof a standard nonsteroid-eluting electrode
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Impedance
• The opposition to current flow
• In a pacing system, impedance is– Measured in ohms– Represented by the letter “R” ( W 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
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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
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Ohm’s Law is a Fundamental Principle of Pacing That:
V
I RV = I X RI = V / RR = V / I
• Describes the relationship between voltage, current, and resistance
x
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Impedance and Electrodes
• Large electrode tip– Threshold ↑– Impedance ↓– Polarization ↓
• Small electrode tip– Threshold ↓– Impedance ↑– Polarization ↑
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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
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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
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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.
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Lead Maturation Process• Effect of Steroid on Stimulation Thresholds
Pulse Width = 0.5 msec
03 6
Implant Time (Weeks)
Textured Metal Electrode
Smooth Metal Electrode
1
2
3
4
5
Steroid-Eluting Electrode
0 1 2 4 5 7 8 9 10 11 12
Vol
ts
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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
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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)
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Intrinsic R wave Amplitude
• Typical intrinsic R wave amplitude measured from pacing leads in the Right Ventricle are more than 5 mV in amplitude
Ampl
itude
Intrinsic R wave in EGM
The Intrinsic R wave amplitude is usually much greater than the T wave amplitude
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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
Vo
lta
ge
Time
Slope
Slew rate=Change in voltage
Time duration ofvoltage change
Slew rate measurements at implant should exceed .5 volts per second for P waves; .75 volts per second for R wave measurements
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Factors That May Affect Sensing Are:• Lead polarity (unipolar vs. bipolar)• Lead integrity
– Insulation break– Wire fracture
• EMI – Electromagnetic Interference
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Undersensing . . .
• Pacemaker does not “see” the intrinsic beat, and therefore does not respond appropriately
Intrinsic beat not sensed
Scheduled pace delivered
VVI / 60
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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
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Signal Amplitude / Slew Rate
Amplitude Range Slew Rate(mV) (v/sec)
Acute Atrial EGM 1.5 - 4.0 0.6 - 1.7
Chronic Atrial EGM 1.0 - 3.0 0.5 - 1.5
Acute Ventricular EGM 7 - 15 0.8 - 2.0
Chronic Ventricular EGM 5 - 12 0.6 - 1.5
Signal
Pacemaker Implantation
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NASPE/ BPEG Generic (NBG) Pacemaker Code
IChamber
Paced
IIChamberSensed
IIIResponseto Sensing
IVProgrammableFunctions/Rate
Modulation
VAntitachy
Function(s)
V: Ventricle V: Ventricle T: Triggered P: Simple programmable
P: Pace
A: Atrium A: Atrium I: InhibitedM: Multi- programmable
S: Shock
D: Dual (A+V) D: Dual (A+V) D: Dual (T+I) C: Communicating D: Dual (P+S)
O: None O: None O: None R: Rate modulating O: None
S: Single (A or V)
S: Single (A or V)
O: None
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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
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Single-Chamber Timing
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Single Chamber Timing Terminology• Lower rate• Refractory period• Blanking period• Upper rate
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Lower Rate Interval
Lower Rate Interval
VP VP VVI / 60
• Defines the lowest rate the pacemaker will pace
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Refractory Period
Lower Rate Interval
VP 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
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Blanking Period
Lower Rate Interval
VP 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 PeriodRefractory Period
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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, SVO2 Peak endocardial acceleration
Tertiary • External changes that result from exercise Vibration
Acceleration
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Upper Sensor Rate Interval
Lower Rate Interval
VP 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 PeriodRefractory Period
Upper Sensor Rate Interval
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VP 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
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Noise Reversion
VPVPSRSR SR SR
Noise Sensed
Lower Rate Interval
VVI/60
• Continuous refractory sensing will cause pacing at the lower rate
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Modes-SINGLE CHAMBER
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AOO & VOO-asynchronous modes
• By application of magnet
• Useful in diagnosing pacemaker dysfunction
• During surgery to prevent interference from electrocautery
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VOO Mode
Blanking Period
VP VP
Lower Rate Interval
VOO / 60
• Asynchronous pacing delivers output regardless of intrinsic activity
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V
VP VPVP
VOO TIMING
VP VP
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VVI Mode
Lower Rate Interval
VP VSBlanking/Refractory
VP
VVI / 60
• Pacing inhibited with intrinsic activity
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V
VP VPVP VPVS
VVI TIMING
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VVIR
VP VP
Refractory/Blanking
Lower Rate
Upper Rate Interval(Maximum Sensor Rate)
VVIR / 60/120Rate Responsive Pacing at the Upper Sensor Rate
• Pacing at the sensor-indicated rate
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AAI• Useful for SSS with N- AV conduction• Should be capable of 1:1 AV to rates 120-140 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
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AAIR
Lower Rate Interval
AP APRefractory/Blanking
Upper Rate Interval(maximum sensor rate)
AAIR / 60 / 120(No Activity)
• Atrial-based pacing allows the normal A-V activation sequence to occur
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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
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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
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Dual Chamber Timing Parameters
• Lower rate• AV and VA intervals• Upper rate intervals• Refractory periods• Blanking periods
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Lower Rate Interval
APVP
APVP
Lower Rate
• The lowest rate the pacemaker will pace the atrium in the absence of intrinsic atrial events
DDD 60 / 120
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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
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APVP
ASVP
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
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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)
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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
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Lower Rate Interval
APVP
APVP
AV Interval VA Interval
Atrial Escape Interval (V-A Interval)Atrial Escape Interval (V-A Interval)
• The interval initiated by a paced or sensed ventricular event to the next atrial event
DDD 60 / 120PAV 200 ms; V-A 800 ms
200 ms 800 ms
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DDDR 60 / 120A-A = 500 ms
APVP
APVP
Upper Activity Rate Limit
Lower Rate Limit
V-APAV V-APAV
Upper Activity (Sensor) Rate
• In rate responsive modes, the Upper Activity Rate provides the limit for sensor-indicated pacing
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ASVP
ASVP
DDDR 60 / 100 (upper tracking rate) Sinus rate: 100 bpm
Lower Rate Interval
Upper Tracking Rate Limit
Upper Tracking Rate
SAV SAVVA 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
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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
VPVentricular Refractory Period (VRP)
A-V Interval(Atrial Refractory)
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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 250-275 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
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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
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PVAB and PVARP
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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)
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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
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PVARP
Upper Tracking Rate
Lower Rate Interval
No SAV started for events sensed in the TARP
AS AS
VPVP
SAV = 200 msPVARP = 300 ms
Thus TARP = 500 ms (120 ppm)
DDDLR = 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
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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
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PVARP
Wenckebach Operation
Upper Tracking Rate
Lower Rate Interval
AS AS AR APVPVP VP
TARPSAV PAV PVARP SAV PVARP
P Wave Blocked (unsensed or unused)
• Prolongs the SAV until upper rate limit expires– Produces gradual change in tracking rate ratio
TARP TARP
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Wenckebach Operation
DDD / 60 / 120 / 310
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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
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• Every other P wave falls into refractory and does not restart the timing interval
Upper Tracking Limit
Lower Rate Interval
P Wave Blocked
AS AS
VPVPARAR
Sinus rate = 133 bpm (450 ms)PVARP = 300 ms SAV = 200 ms
TARP=500 ms
AV PVARP AV PVARP
TARP TARP
2:1 Block
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2:1 Block
DDD / 60 / 120 / 310
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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
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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
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Ventricular Safety Pace
DDD 60 / 120
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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)
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VDD
Upper Tracking Limit
VDDLR = 60 ppmUTR = 120 ppmSpontaneous A activity = 700 ms (85 ppm)
Lower Rate Interval
AS AS
VPVP VP
• Provides atrial synchronous pacing – System utilizes a single lead
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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
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Rate (sinus driven) = 70 bpm / 857 msSpontaneous conduction at 150 msA-A = 857 ms
ASVS
ASVS
V-AAV AV V-A
• Atrial Sense, Ventricular Sense (AS/VS)
Four “Faces” of Dual Chamber Pacing
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Rate = 60 bpm / 1000 msA-A = 1000 ms
APVP
APVP
V-AAV V-AAV
• Atrial Pace, Ventricular Pace (AP/VP)
Four “Faces” of Dual Chamber Pacing
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Rate = 60 ppm / 1000 msA-A = 1000 ms
AP VS
AP VS
V-AAV V-AAV
• Atrial Pace, Ventricular Sense (AP/VS)
Four “Faces” of Dual Chamber Pacing
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ASVP
ASVP
Rate (sinus driven) = 70 bpm / 857 msA-A = 857 ms
• Atrial Sense, Ventricular Pace (AS/ VP)
V-AAV AV V-A
Four “Faces” of Dual Chamber Pacing
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Mode Selection
DDIR DDDR
N
VVIVVIR
Are they chronic?
Y
Y N
DDD, VDDDDDR DDDR
Y N
Is AV conduction intact?
Is SA node functionpresently adequate?
Symptomaticbradycardia
Are atrial tachyarrhythmias
present?
Is SA node functionpresently adequate?
Is AV conduction intact?
Y
Y N
AAIRDDDR
DDDR, DDIR
N N(SSS)
N
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Optimal Pacing Mode (BPEG)
• Sinus Node Disease - AAI (R)• AVB - DDD• SND + AVB - DDDR + DDIR• Chronic AF + AVB - VVI
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Thank u
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Mode Selection Decision TreeDDIR with SV PVARP
DDDR withMS
N
VVIVVIR
Are they chronic?
Y
Y N
DDD, VDDDDDR DDDR
Y N
Is AV conduction intact?
Is SA node functionpresently adequate?
Symptomaticbradycardia
Are atrial tachyarrhythmias
present?
Is SA node functionpresently adequate?
Is AV conduction intact?
Y
Y N
AAIRDDDR
DDD, DDIwith RDR
N N(SSS) (CSS,VVS)
N
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Stuart Allen 06
Pacing ModesPacing Modes
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Output circuit
VVI
AMP
Ventricular Demand
Programmed lower rate 50 mm/s
VVI
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Stuart Allen 06
Output circuit
VVIR
AMP
Sensor
Ventricular DemandPacing Modesp
Programmed lower rate 50 mm/s
Sensor indicatedrate
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Stuart Allen 06
Output circuit
AAI
AMP
Atrial Demand
Programmed lower rate 50 mm/s
AAI
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Stuart Allen 06
Pacing Modes - Summary
Output circuit
VAT
AMP
Atrial Synchronised
Output circuit
AAI
AMP
Atrial Demand
Output circuit
DVI
AMP
A-V SequentialOutput circuit
Output circuit
VDD
AMP
Atrial synchronisedVentricular Inhibited
AMP
Output circuit
DDD
AMP
A-V UniversalOutput circuit
Timing & Control
AMP
Output circuit
VVI
AMP
Ventricular Demand