Advanced Pacemaker Operations
Module 7
1
Objectives
• Define: Blanking and refractory
• Complete VVI and DDD timing diagrams
– Correctly identifying PVARP, PVAB, PPAB, and TARP
– Identify events in refractory and blanking, and their effect on timing
– Correctly identify Marker Channel™ notations
• Identify upper rate behaviors
– Calculate 2:1 vs. Wenckebach rates
2
Marker Channel
™
• Very useful in helping you understand how the IPG is
interpreting events
• Each manufacturer has its own code
• Medtronic’s code:
– AS  Atrial Sense
– AP  Atrial Pace
– AR  Atrial Refractory
– VS  Ventricular Sense
– VP  Ventricular Pace
– VR  Ventricular Refractory
3
What Do You Think Would Happen Next If…
• The QRS was sensed by the atrial channel?
A
P
A
S
DDD 60
V
P
Note: The Marker Channel tells you how
the pacemaker is interpreting these
events.
Click for Answer
The next atrial pace would be inhibited because the pacemaker
thinks the QRS is a P-wave.
Obviously, this is not how we want a DDD pacemaker to behave.
This was a problem in early pacemakers.
4
What Do You Think Would Happen Next If…
• These T-waves were sensed by the ventricular
channel?
Actual Rate: 50 bpm or 1200 ms
Programmed: VVI 60
Click for Answer
V
P
V
S
V
P
V
S
5
Blanking and Refractory Periods
• Blanking Period
– A period of time during which the sense amplifiers are off, and the
pacemaker is “blind”
– Some blanking periods are programmable, some are nonprogrammable
• Refractory Period
– A period of time during which sensed events are ignored for timing
purposes, but included in diagnostic counters
– Some refractory periods are programmable, some nonprogrammable
6
Why Do We Use Refractory and Blanking Periods?
• Pacemaker sensing occurs when a signal is large enough
to cross the sensing threshold
5.0 mV
Sensing does not tells us
anything about the origin or
morphology of the sensed
event, only its “size.”
2.5 mV
1.25 mV
1.25 mV Sensitivity
Time
7
Why Do We Use Refractory and Blanking Periods?
• By manipulating the sense amplifiers, we filter signals
based on their relationship
The potential for digitizing
these signals may
someday allow
pacemakers to discriminate
signals based on
morphology rather than just
on their relationship.
5.0 mV
2.5 mV
SENSE!
1.25 mV
Sensing
Blanking
Refractory
Time
8
Let’s Look at the VVI Example Again…
• Now, is the T-wave sensed by the ventricular channel?
VVI 60
V
P
V
R
V
P
V
R
Click for Answer
The T-wave falls in the ventricular refractory period (VR), and it is
ignored for timing purposes.
The VVI pacemaker is operating normally.
9
VVI Timing
• Note the addition of the Blanking and Refractory periods
1000 ms
1000 ms
VRP 320 ms
Blanking
V
P
VRP 320 ms
V
R
V
P
V
R
Refractory
The pacemaker applies these
periods to every timing cycle.
10
T-wave Sensing
• Is there another way to program the pacemaker to ignore
the T-waves?
Click for Answer
1000 ms
1000 ms
VRP 320 ms
Blanking
V
P
V
R
VRP 320 ms
Refractory
V
P
V
R
We could program the pacemaker to be less sensitive (e.g., from
2.5mV to 5.0 mV). But then it might not sense every R-wave.
11
Dual Chamber Timing
Refractory and Blanking Periods
PVAB
ARP
PVARP
VRP
Those affecting the atrial
channel are indicated above
the ECG baseline.
Those affecting the ventricular
channel are indicated below
the ECG baseline.
Red: Blanking
Orange: Refractory period
12
Dual Chamber Timing
Post Ventricular
Atrial Blanking
• Atrial Refractory and
Blanking Periods
Atrial
Blanking
PVAB
ARP
PVARP
VRP
Atrial
Refractory
Period
Post Ventricular Atrial
Refractory Period
13
Dual Chamber Timing
• Ventricular Refractory and Blanking Periods
PVAB
ARP
Post Atrial
Ventricular
Blanking
PVARP
VRP
Ventricular Refractory
Period
Ventricular
Blanking
14
Dual Chamber Timing
• Atrial Pace (AP) - Ventricular Pace (VP) example
A-A interval
A-A interval
DDD 60
V-A interval
PAV
V-A interval
PAV
PVAB
ARP
PVAB
PVARP
VRP
ARP
PVARP
VRP
The pacemaker applies these periods every timing cycle.
15
Dual Chamber Timing
• Lower Rate (A-A) Interval
– A-A interval indicates the minimum rate the device will pace under
normal circumstances (“escape interval,” “lower rate interval”)
– In dual chamber pacemakers we subdivide this into the A-V interval
(PAV or SAV) and the V-A interval
• Normally, the device is designed to always use A-A timing – to maintain
a steady atrial rate
A-A interval
A-A interval
V-A interval
PAV
V-A interval
PAV
PVAB
PVAB
PVARP
ARP
VRP
PVARP
ARP
VRP
16
Dual Chamber Timing
• Upper Tracking Rate (UTR)
– The maximum rate the ventricles will be paced 1:1 in response to
atrial sensed events
A-A interval
A-A interval
V-A interval
V-A interval
SAV
SAV
UTR
UTR
PVAB
ARP
PVAB
PVARP
VRP
ARP
PVARP
VRP
17
Dual Chamber Timing
• Tracking
– 1:1 tracking (atrial sense – ventricular pace) occurs at rates above
the Lower Rate, but below the Upper Tracking Rate
A-A interval
A-A interval
UTR
PVAB
PVARP
ARP
VRP
1:1 tracking of
any atrial sense
18
Dual Chamber Timing
• The pacemaker’s response to high atrial rates
– To a pacemaker, an increase in atrial rate means that V-A intervals
are getting shorter
A-A interval
A-A interval
V-A interval
SAV
V-A interval
SAV
UTR
UTR
PVAB
PVAB
PVARP
ARP
VRP
PVARP
ARP
VRP
In other words, the next atrial sense is getting closer to the previous
ventricular event.
19
Dual Chamber Timing
Upper Rate Behavior
20
Upper Rate Behavior
• Pacemaker Wenckebach
– Caused by the atrial rate exceeding the Upper Tracking Rate
21
Upper Rate Behavior
• Pacemaker Wenckebach
– Prolongs the SAV until upper rate limit expires
– Produces gradual change in tracking rate ratio
A-A interval
A-A interval
UTR
UTR
A
S
A
S
ARP
PVARP
SAV
A
R
ARP
PVARP
SAV
V
P
A-A interval
UTR
A
P
ARP
PVARP
PAV
V
P
V
P
22
Wenckebach Example
• Pacemaker patient on an exercise test
– 4:3 Wenckebach operation
• Each AS (P-wave) is followed by an increasing SAV, and then the VP
• Eventually an atrial beat is not tracked, and a ventricular beat is dropped
23
Wenckebach Example
This P-wave fell in the
PVARP of the previous
cycle.
It is refractory (AR), so it
is ignored for timing.
It cannot start an SAV, so
it is not followed by a
ventricular pace.
This is normal upper rate
pacemaker behavior.
24
Upper Rate Behavior
• 2:1 Block
– Occurs when P-waves are faster than TARP
– TARP = SAV + PVARP
ARP
PVARP
ARP
PVARP
TARP
A
S
TARP
A
R
SAV
A
S
TARP
A
R
SAV
V
P
ARP
A
S
SAV
V
P
V
P
25
Upper Rate Behavior
• 2:1 Block
– Caused by the atrial rate exceeding the Total Atrial Refractory
Period (TARP)
26
Knowledge Check
• Given the following
pacemaker parameters, what
rhythm will result from an
atrial rate of 130 bpm?
– UTR = 120 bpm
– SAV = 150 ms
– PVARP = 250 ms
• Given the same pacemaker
parameters, what atrial rate
would result in 2:1 block?
Click for Answer
– An atrial rate above 150 bpm
Click for Answer
– Pacemaker Wenckebach
27
Upper Rate Behavior
Ventricular Rate
UTR
LR
1:1 Atrial
Tracking
No
Ventricular
Pacing
LR
Wenckebach
UTR
2:1 Block
TARP
Atrial Rate
= Ventricular Pacing
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Upper Rate Behavior
Ventricular Rate
UTR
LR
1:1 Atrial
Tracking
No
Ventricular
Pacing
LR
= Ventricular Pacing
Wenckebach
UTR
2:1 Block
TARP
Atrial Rate
29
Achieving a Higher UTR without Block
• Decrease SAV
ARP
• Decrease PVARP
PVARP
ARP
TARP
A
S
TARP
A
R
A
S
SAV
ARP
SAV
A
R
SAV
PVARP
ARP
Increased
Tracking
TARP
A
S
PVARP
A
S
SAV
PVARP
Increased
Tracking
TARP
A
S
A
S
SAV
SAV
30
Achieving a Higher UTR without Block
• SAV and PVARP managed automatically
– Programming Rate-Adaptive AV to “On”
• This will automatically decrease the SAV/PAV as the atrial rate
increases
– Programming PVARP to “Auto”
• This will automatically decrease the PVARP as the atrial rate increases
31
If Long TARP is the Problem…
• Why not just program short AV Intervals or short PVARP?
– Short AV intervals may force ventricular pacing
– Short PVARP may allow retrograde conduction to be sensed
• Consider this ECG:
• The retrograde P-waves
occur outside of PVARP.
• The pacemaker tracks
the retrograde P-waves.
• This is called a
Pacemaker Mediated
Tachycardia (PMT).
32
Status Check
Can you identify the following
Marker Channel notations?
Click for Answer
AS
An Atrial Sense (P-wave)
VR
Ventricular Refractory
AR
Atrial Refractory
AP
Atrial Pace
VP
Ventricular Pace
VS
A Ventricular Sense (QRS or
R-wave)
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Status Check
Can you complete this timing diagram?
Click for Answer
Lower Rate Interval
Lower Rate Interval
VRP
V. Blanking
VRP
V. Blanking
V
P
V
P
34
Status Check
Complete this timing diagram
• Show:
- Atrial Refractory during the AV Interval
Atrial Refractory during the AV Interval
- PVARP with PVAB
PVARP with PVAB
- VRP
VRP
Click for Answer
35
Status Check
• You are called to evaluate this rhythm strip
– Obtained while the patient is having an exercise test
– Clinician thinks it is loss of capture
– Patient’s underlying rhythm is CHB
• What is going on?
Click for Answer
2:1 block. P-waves
36
Status Check
• What mode do you think this is?
• Calculate the Atrial and Ventricular rates
• Propose a programming solution to resolve this
430 ms
Click for Answer
860 ms
DDD Mode. Atrial rate: 430 ms or 140 bpm, Ventricular
rate: 860 ms or 70 bpm.
Increase the UTR and program RA-AV on, or Increase
UTR and decrease PVARP.
37
Status Check
• Given the following parameters, what will occur first as the
patient’s atrial rate increases? Wenckebach or 2:1 block?
– Upper Tracking Rate: 120 bpm
– SAV = 200 ms
– PVARP = 350 ms
Click for Answer
• 2:1 block will occur first
38
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.
39
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.
40
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.
41
Brief Statement: Medtronic Leads (continued)
Warnings/Precautions
• People with metal implants such as pacemakers, implantable cardioverter defibrillators (ICDs), and
accompanying leads should not receive diathermy treatment. The interaction between the implant and
diathermy can cause tissue damage, fibrillation, or damage to the device components, which could
result in serious injury, loss of therapy, or the need to reprogram or replace the device.
• For the SelectSecure Model 3830 lead, total patient exposure to beclomethasone 17,21-dipropionate
should be considered when implanting multiple leads. No drug interactions with inhaled
beclomethasone 17,21-dipropionate have been described. Drug interactions of beclomethasone
17,21-dipropionate with the Model 3830 lead have not been studied.
Potential Complications
• Potential complications include, but are not limited to, valve damage, fibrillation and other arrhythmias,
thrombosis, thrombotic and air embolism, cardiac perforation, heart wall rupture, cardiac tamponade,
muscle or nerve stimulation, pericardial rub, infection, myocardial irritability, and pneumothorax.
Other potential complications related to the lead may include lead dislodgement, lead conductor
fracture, insulation failure, threshold elevation or exit block.
• See specific 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 this device to sale by or on the order of a physician.
42
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.
43