Pacemaker Automatic Features
Module 10
1
Topics
• Atrial and Ventricular Capture Management®
• Sensing Assurance
• Auto Adjusting Sensitivity
• Lead Monitor and Polarity Switch
• Rate Response
2
Capture Management® Objectives
• Describe the value of Atrial and Ventricular Capture
Management®
• Recall the basic operation of ACM and VCM
• Identify how to program ACM and VCM
3
Capture Management®
• Why is it important?
– Patient Safety
– Device Longevity
– Troubleshooting Information
• How is it conducted?
– Automatic algorithms that mimic what a person would do in a clinic
4
Capture Management® - Three Categories
Assess Patient’s
Rhythm
Determine
Threshold
Program
Appropriately
5
Capture Management®
Manual Testing
Assess patient’s rhythm (rate,
type)
Assess Patient’s
Rhythm
Determine
Threshold
Program
Appropriately
Automated Testing
Stability Check
6
Capture Management®
Assess Patient’s
Rhythm
Determine
Threshold
Would you run a ventricular threshold test on a patient whose
underlying rhythm is AF with a ventricular response of 120 bpm?
Program
Appropriately
NO
• When you get ready to run a threshold test manually:
– What questions do you ask?
– Why do you ask these questions?
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Capture Management®
Assess Patient’s
Rhythm
Determine
Threshold
Program
Appropriately
• VCM Stability check
– Are conditions favorable to conduct a search?
• What is the rate? (typically lower than 90 – 100 bpm)
• What is rhythm? (defined by few VR/AR/VSP/PVC)
• Are there feature interaction? (No RDR or Mode Switch in
progress)
– If conditions are unfavorable, what do you think happens?
• The threshold test is postponed
– If conditions are favorable
• Move on to determining the threshold
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Capture Management®
Manual Testing
Assess Patient’s
Rhythm
Determine
Threshold
Program
Appropriately
Automated Testing
Decide how to pace
Decide how to pace
Choose the type of testamplitude decrement, pulse
width decrement, or strength
duration
Choose the type of testalways strength duration
Start pacing
Test paces, backup paces,
and support cycles
Threshold search
Threshold search
Identify Loss of Capture (LOC)
Evoked response sensing
Call capture threshold one step
above LOC
Confirm capture at one step
above LOC
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Capture Management®
Assess Patient’s
Rhythm
Determine
Threshold
Program
Appropriately
• Decide how to pace
– Why do you need to decide how to pace?
• To force pacing
– What are your options for forcing pacing?
• Increase the rate in a non-tracking mode (VVI/R, DDI/R)
– How much?
• Decrease the AV delay in a tracking mode (DDD/R)
– How much?
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Capture Management®
Assess Patient’s
Rhythm
Determine
Threshold
Program
Appropriately
• Choose the type of test
– The device runs a strength duration test for Ventricular Capture
Management
1.50
V
1.2
5V
1.0
V
0.7
5V
0.
5
V
Pulse
Width
Threshold
Amplitude
Threshold
0.4 ms
1.0 ms
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Capture Management®
Assess Patient’s
Rhythm
Determine
Threshold
Program
Appropriately
• Test paces, backup paces, and support cycles
Q: If you start running a threshold test on a pacer dependent
patient, and immediately see Loss of Capture, what do you do?
A: Stop the test
• Test pace- pace delivered to determine capture
• Backup pace- pace delivered immediately following each
test pace to ensure there are no dropped beats
12
Capture Management®
Assess Patient’s
Rhythm
Determine
Threshold
Program
Appropriately
• Test paces, backup paces, and support paces
Q: As you are running a threshold test on a patient at
an accelerated rate to force pacing, the patient becomes
extremely symptomatic, what do you do?
A: Stop the test
• Support cycles- a series of three events (paced or sensed)
that allow for the heart to function as it would without being
tested
13
Ventricular Capture Management®
Test & Back-up
Pace
Support
Events
Test & Back-up
Pace
14
Capture Management®
Assess Patient’s
Rhythm
Determine
Threshold
Program
Appropriately
Threshold Search
Starting
Output
Decrement
Output
Ending
Output
• Starting Output
– Start at an output that capture
should occur
When you are performing a threshold,
how do you shorten the test?
– Capture Management® starts its
threshold search at the previous
measured threshold value
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Capture Management®
Assess Patient’s
Rhythm
Determine
Threshold
Program
Appropriately
Threshold Search
Starting
Output
• Decrement Output
– Lower output (amplitude or pulse
width) one step at a time
Decrement
Output
– Ventricular Capture Management®
performs Strength Duration Test
• Tests amplitude at 0.4 ms PW
• Tests PW at 2X amplitude
threshold
Ending
Output
– Atrial Capture Management®
performs an Amplitude Decrement
Test
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Capture Management®
Assess Patient’s
Rhythm
Determine
Threshold
Program
Appropriately
Threshold Search
Starting
Output
Decrement
Output
• Ending Output
What do you do when you see Loss
of Capture (LOC)?
Programmer
Analyzer
Stop the test
Increase output
to confirm
capture
Ending
Output
• Capture Management® confirms
capture
17
Capture Management®
• Identify Loss of Ventricular Capture
How do you identify Loss of Capture (LOC) when
running a ventricular pacing threshold?
VVI
DDD
vs.
18
Evoked Response Sensing
• All ventricular capture verification algorithms:
– Rely on sensing the evoked response to the test pace
– The characteristics of this response is how the pacemaker
determines if the myocardium is captured
– If the characteristics of the evoked response signal differ from what
is expected, the pacemaker assumes LOC
– Evoked response sensing can be affected by
• Lead tissue interface (acute vs. chronic lead)
• Lead Polarization
• Tip-to-Ring spacing
• Lead tip design
• Other factors
19
Capture Management®
• Identify Loss of Atrial Capture
How do you identify capture when you run an
atrial pacing threshold?
20
Capture Management®
• Atrial Chamber Reset Method
– Device makes sure that there are no intrinsic atrial events competing
with the pacing rate
Test AP
No Atrial Sense
in the AV Interval
(Capture)
21
Capture Management®
• AV Conduction Method
– Device looks for a conducted R-wave at the predicted time after an
atrial pace
AP-VS interval following test pace is monitored; if timing is consistent
with support pace “expected” window, device records as capture.
AP-VS events that result from back-up paces (LOC) will lag by
approximately 70 ms from the “expected” window of a test pace.
22
Capture Management®
Manual Testing
Program appropriate safety
margin
Assess Patient’s
Rhythm
Determine
Threshold
Program
Appropriately
Automated Testing
Follow programmed
rules
23
Capture Management®
Assess Patient’s
Rhythm
Determine
Threshold
Program
Appropriately
• Adapts the output downward in one step decrements
(0.125V)
– Never below the programmable Minimum Amplitude (Nominal =
2.5V)
– Applies the programmable safety margin (Nominal = 2X) to the
amplitude at 0.4 ms pulse width
• Adapts upward, as needed, to maintain the safety margin
• Acute Phase
– Output may rise
– Will not adapt downward until the Acute Phase expires (N=112
days)
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Advanced Pacemaker Operations
Tools to Manage Pacemaker Sensing
25
Sensitivity Management Objectives
• State a reason why fixed sensing safety margins may not
be adequate
• Identify three clinical areas affected by inappropriate
sensing
• Recall two of the mechanisms for managing sensing
automatically
26
Sensitivity Management
What factors can change a patient’s P- and Rwave amplitudes?
Lead
Maturation
Myocardial
Infarction
Atrial
Arrhythmia
s
Antiarrhythmia
Medications
Ventricular
Arrhythmia
s
Exercise
• Programming a fixed sensing safety margin may not
accommodate for these and other potential changes
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Sensitivity Management
Normal
Operation
Therapy
Diagnostics
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Sensitivity Management
• Sensing Assurance
– Adapts Sensitivity based on target safety margins, to automatically
provide safe sensing margins
Atrial Bipolar
High
5.6x
Sensitivity
4x
Sensitivity
Current
Sensitivity
Adequate
Low
2.8 mV
2.0 mV
0.5 mV
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Sensitivity Management
• Auto Adjusting Sensitivity
– Adjusts the sensitivity fence on a beat-by-beat basis
30
Rate Response
31
Rate Response Objectives
• State the clinical reason for rate response pacing
• Recall why rate response pacing works
• List the implantations industry uses for rate response
pacing
32
Rate Responsive Pacing
• Introduced in the mid-80’s by Medtronic
– Why was it one of the most significant developments in pacing?
• When one exercises, metabolic demand increases. To meet this
demand, cardiac output needs to increase.
– What contribution does increasing heart rate make to increasing the
cardiac output?
Click for Answer
Up to a 500% increase over the resting cardiac output. No other
component of cardiac output has this significant of a contribution.
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Rate Responsive Pacing
• This is designated by the “R” in DDDR, AAIR, or VVIR…
– It is accomplished by using a sensor to indicate changing metabolic
demand
– The sensor then modifies the pacing rate
– Think of it as a dynamic lower rate or dynamic escape interval
• DDDR 60 -130 means:
– The heart will not be paced at rates below 60 bpm
– The heart may be paced at rates between 60 -130 bpm, based on
the information from the rate response sensor
– The heart will not be paced at rates above 130 bpm
34
Rate Response Sensors
Many types have been developed with various advantages and disadvantages
Motion-based
Sensors
Advantages
Disadvantages
• Piezoelectric
Fast to respond, easy to program,
less expensive to make
Motion based. May not be as
accurate with sustained
exercise.
Fast to respond, easy to program,
less expensive to make
Motion based. May not be as
accurate with sustained
exercise.
Accurate, uses rate and depth of
respirations
Slow to respond, increased
battery consumption
• Q-T interval
Accurate
Slow to respond, requires
Ventricular Pacing
• Temperature
Not always reliable
Increased battery consumption,
special lead
crystal
• Accelerometer
Metabolic Sensors
• Minute Ventilation
(MV)
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Rate Response Sensors
• In use today
– Accelerometer
– Piezo-electric crystal
– Combination of MV + Accelerometer or MV + P-E crystal
– Combination of QT + Piezo-electric crystal
36
Rate Response
• Rate responsive (also called rate modulated) pacemakers
provide patients with the ability to vary heart rate when the sinus
node cannot provide the appropriate rate
• Rate responsive pacing is for patients who may benefit
from increased pacing rates concurrent with increases in
activity, such as:
– Patients who are chronotropically incompetent (heart rate cannot
reach appropriate levels during exercise, or meet other metabolic
demands)
– Patients in chronic atrial fibrillation with too slow of a ventricular
response to meet metabolic demands
37
Rate Responsive Pacing
• Cardiac output (CO) is determined by the combination of
stroke volume (SV) and heart rate (HR)
• SV X HR = CO
• Changes in cardiac output depend on the ability of the HR
and SV to respond to metabolic requirements
38
Rate Responsive Pacing
• SV reserves can account for increases in cardiac output of
up to 50%
• HR reserves can nearly triple total cardiac output in
response to metabolic demands
39
Rate Responsive Pacing
• When the need for oxygenated blood increases, the
pacemaker ensures that the heart rate increases to
provide additional cardiac output
Adjusting Heart Rate to Activity
Normal Heart Rate
Rate Responsive Pacing
Fixed-Rate Pacing
Daily Activities
40
A Variety of Rate Response Sensors Exist
• Those most accepted in the market place are:
– Activity sensors that detect physical movement and increase the rate
according to the level of activity
– Minute ventilation sensors measure the change in respiration rate
and tidal volume via transthoracic impedance readings
41
Rate Responsive Pacing
• Activity sensors employ a
piezoelectric crystal that
detects mechanical signals
produced by movement
• The crystal translates the
mechanical signals into
electrical signals that in
turn increase the rate of the
pacemaker
Piezoelectric
crystal
42
Rate Responsive Pacing
• Minute Ventilation (MV) is the volume of air introduced into
the lungs per unit of time
• MV has two components:
– Tidal volume - the volume of air introduced into the lungs in a single
respiration cycle
– Respiration rate - the number of respiration cycles per minute
43
Rate Responsive Pacing
• Minute ventilation can be measured by calculating the
changes in electrical impedance across the chest cavity to
calculate changes in lung volume over time
44
Status Check
• Evaluate this rhythm strip
– IPG is programmed to 60-130bpm
– What are the atrial and ventricular rates?
Click for Answer
– What operation is in effect?
• A and V rates are about 79 bpm
• Rate responsive pacing in the atrium with intrinsic AV conduction
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Brief Statements
Indications
•
Implantable Pulse Generators (IPGs) are indicated for rate adaptive pacing in patients who ay benefit from increased
pacing rates concurrent with increases in activity and increases in activity and/or minute ventilation. Pacemakers are
also indicated for dual chamber and atrial tracking modes in patients who may benefit from maintenance of AV
synchrony. Dual chamber modes are specifically indicated for treatment of conduction disorders that require restoration
of both rate and AV synchrony, which include various degrees of AV block to maintain the atrial contribution to cardiac
output and VVI intolerance (e.g. pacemaker syndrome) in the presence of persistent sinus rhythm.
•
Implantable cardioverter defibrillators (ICDs) are indicated for ventricular antitachycardia pacing and ventricular
defibrillation for automated treatment of life-threatening ventricular arrhythmias.
•
Cardiac Resynchronization Therapy (CRT) ICDs are indicated for ventricular antitachycardia pacing and ventricular
defibrillation for automated treatment of life-threatening ventricular arrhythmias and for the reduction of the symptoms of
moderate to severe heart failure (NYHA Functional Class III or IV) in those patients who remain symptomatic despite
stable, optimal medical therapy and have a left ventricular ejection fraction less than or equal to 35% and a QRS
duration of ≥130 ms.
•
CRT IPGs are indicated for the reduction of the symptoms of moderate to severe heart failure (NYHA Functional Class
III or IV) in those patients who remain symptomatic despite stable, optimal medical therapy, and have a left ventricular
ejection fraction less than or equal to 35% and a QRS duration of ≥130 ms.
Contraindications
•
IPGs and CRT IPGs are contraindicated for dual chamber atrial pacing in patients with chronic refractory atrial
tachyarrhythmias; asynchronous pacing in the presence (or likelihood) of competitive paced and intrinsic rhythms;
unipolar pacing for patients with an implanted cardioverter defibrillator because it may cause unwanted delivery or
inhibition of ICD therapy; and certain IPGs are contraindicated for use with epicardial leads and with abdominal
implantation.
•
ICDs and CRT ICDs are contraindicated in patients whose ventricular tachyarrhythmias may have transient or
reversible causes, patients with incessant VT or VF, and for patients who have a unipolar pacemaker. ICDs are also
contraindicated for patients whose primary disorder is bradyarrhythmia.
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Brief Statements (continued)
Warnings/Precautions
• Changes in a patient’s disease and/or medications may alter the efficacy of the device’s programmed
parameters. Patients should avoid sources of magnetic and electromagnetic radiation to avoid
possible underdetection, inappropriate sensing and/or therapy delivery, tissue damage, induction of an
arrhythmia, device electrical reset or device damage. Do not place transthoracic defibrillation paddles
directly over the device. Additionally, for CRT ICDs and CRT IPGs, certain programming and device
operations may not provide cardiac resynchronization. Also for CRT IPGs, Elective Replacement
Indicator (ERI) results in the device switching to VVI pacing at 65 ppm. In this mode, patients may
experience loss of cardiac resynchronization therapy and / or loss of AV synchrony. For this reason,
the device should be replaced prior to ERI being set.
Potential complications
• Potential complications include, but are not limited to, rejection phenomena, erosion through the skin,
muscle or nerve stimulation, oversensing, failure to detect and/or terminate arrhythmia episodes, and
surgical complications such as hematoma, infection, inflammation, and thrombosis. An additional
complication for ICDs and CRT ICDs is the acceleration of ventricular tachycardia.
• See the device manual for detailed information regarding the implant procedure, indications,
contraindications, warnings, precautions, and potential complications/adverse events. For further
information, please call Medtronic at 1-800-328-2518 and/or consult Medtronic’s website at
www.medtronic.com.
Caution: Federal law (USA) restricts these devices to sale by or on the order of a physician.
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Brief Statement: Medtronic Leads
Indications
• Medtronic leads are used as part of a cardiac rhythm disease management system. Leads are
intended for pacing and sensing and/or defibrillation. Defibrillation leads have application for patients
for whom implantable cardioverter defibrillation is indicated
Contraindications
• Medtronic leads are contraindicated for the following:
• ventricular use in patients with tricuspid valvular disease or a tricuspid mechanical heart valve.
• patients for whom a single dose of 1.0 mg of dexamethasone sodium phosphate or dexamethasone
acetate may be contraindicated. (includes all leads which contain these steroids)
• Epicardial leads should not be used on patients with a heavily infracted or fibrotic myocardium.
• The SelectSecure Model 3830 Lead is also contraindicated for the following:
• patients for whom a single dose of 40.µg of beclomethasone dipropionate may be contraindicated.
• patients with obstructed or inadequate vasculature for intravenous catheterization.
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Disclosure
NOTE:
This presentation is provided for general educational purposes
only and should not be considered the exclusive source for this
type of information. At all times, it is the professional
responsibility of the practitioner to exercise independent
clinical judgment in a particular situation.
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