Special Timing Functions

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• Special Timing Functions
• PMT
• PVC
• Crosstalk
• Auto Ventricular Blanking

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• Pacemaker - Mediated Tachycardia
• Initiation
• Prevention
• Detection
• Therapy

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PMT Endless Loop Tachycardia
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PMT Endless Loop Tachycardia
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PMT Endless Loop Tachycardia
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PMT - Conditions to be fulfilled

• Initiator
• Retrograde (VA) conduction
• VDD or DDD Pacemaker

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PMT Cycle Length

• PMT cycle time
• VA conduction time
• programmed AV delay
• (or Maximum Tracking Rate interval)

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PMT Endless Loop Tachycardia

• Initiation
• PVC
• Atrial undersensing
• Atrial oversensing
• Atrial noncapture
• Long AV delay

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PMT Initiation by PVC
PVC
Surface ECG
Retrograde P-waves
Esophageal ECG
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PMT Initiation by PVC
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PMT Initiation
Atrial noncapture causes ventricular
stimulation without the AV node being blocked by
anterograde event
Atrial oversense Inhibits atrial output causes
ventricular stimulation without the AV node being
blocked by anterograde event
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PMT Initiation by loss of atrial capture
Surface ECG
Retrograde P-waves
Esophageal ECG
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PMT Initiation
Atrial undersense Results in a long AV interval,
allowing the AV node time to recover and conduct
retrograde
Long AVI Allows the AV node time to recover
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PMT Initiation by loss of atrial sensing
AP
AS
AS
AS
AS
AS
AS
AS
AS
AS
VP
VP
VP
VP
VP
VP
VP
VP
VP
VP
Surface ECG
Retrograde P-waves
Esophageal ECG
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PMT Endless Loop Tachycardia

• Prevention (not SJM specific)
• PVARP
• PVARP extension after PVC
• Differential atrial sensing anterograde /
  retrograde p-wave morphology comparison
• Rate adaptive PVARP
• High max tracking rate retrograde fatigue

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PMT Endless Loop Tachycardia

• Detection
• P tracking at upper rate limit
• P tracking at intermediate rate
• AV interval modulation
• Discrepancy between sensed atrial rate and sensor
  indicated rate

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PMT Options SJM

• Off (nominal for Identity and Integrity)
• 10 Beats gt PMT
• Auto detect (nominal for Zephyr and Victory)
• No PMT options during AMS or Magnet Application

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PMT Options SJM - 10 Beats gt PMT

• Detection
• 10 consecutive AS-VP events at a rate gt PMT
  Detection Rate
• PMT Detection Rate 90 150 bpm, nominal 110
• Response
• Reset of PVARP to 480 ms for a single cycle
• After PVARP extension
• PMT detection is suspended for 256 cycles
• the atrial alert period is 330 ms

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10 Beats gt PMT
PVARP 480ms Atrial Alert Period 330ms
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PMT Options SJM Auto Detect

• Detection
• Rapid stable VP AS interval
• Rapid atrial rate gt PMT Detection Rate
• Stable compares average of 8 VP AS intervals
  to average of all cycles. If all VP - AS
  intervals are with 16 ms of average ? stable
• On the 9th cycle the AS VP delay is
• Shortened 50 ms if AS VP ? 100 ms
• Lengthened 50 ms if AS VP lt 100 ms
• If VP AS cycle is within 16 ms of average VP
  AS cycle ? PMT. Else ? Sinus Tachycardia

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PMT Options SJM Auto Detect
(VP-AS)1
(VP-AS)2
(VP-AS)1 ? (VP-AS)2 therefore sinus tachycardia
AS - VP
AS - VP
(AS-VP) - ?
(VP-AS)1 (VP-AS)2 therefore PMT
AS - VP
AS - VP
(AS-VP) - ?
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PMT Options SJM Auto Detect
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PMT Endless Loop Tachycardia

• Termination
• PVARP extension
• Withhold of ventricular output
• Withhold of ventricular output with early atrial
  pace

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PMT Options SJM Auto Detect and Response

• Response
• After 9th interval no ventricular response
• Atrial pulse 330 ms after retrograde P-wave

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PMT Option Auto Detect
AVI 50ms
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• Special Timing Functions
• PMT
• PVC
• Crosstalk
• Auto Ventricular Blanking

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PVC Options

• To distinguish between a premature ventricular
  contraction (PVC) and a conducted R-wave in
  DDD(R) or VDD(R) mode
• A response to a PVC to prevent the evolution into
  a PMT

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PVC Detection

• A PVC is confirmed if
• An R-wave is not preceded by an atrial event
• Or
• A P-wave is detected in the relative portion of
  the PVARP but is not followed by an R-wave within
  280ms of the atrial event

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PVC Options PVARP on PVC

• After PVC Detection
• PVARP extension to 480 ms
• Followed by atrial alert period of 330 ms

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PVC Options Atrial Pace on PVC

• After PVC Detection
• PVARP extension to 480 ms
• If retrograde P-wave is detected PVARP is
  terminated
• No ventricular output
• Atrial Escape Interval 330 ms

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Atrial Pace on PVC
DDD 60
330ms
Extension of PVARP to 480 Atrial Alert Period of
330ms
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• Special Timing Functions
• PMT
• PVC
• Crosstalk
• Auto Ventricular Blanking

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Whats up Doc?
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Crosstalk

• Sensing of an atrial output in the ventricular
  channel resulting in inhibition of the
  ventricular pulse
• Clinical manifestation atrial pacing with no
  ventricular output. Can be overcome with
  Ventricular Safety Standby
• Crosstalk can occurs with
• High atrial pulse amplitude
• High ventricular sensitivity
• Short ventricular blanking
• Rapid pacing rates
• Unipolar pacing and sensing

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Crosstalk

• Decrease atrial output?
• Decrease ventricular sensitivity?
• Prolong ventricular blanking?
• Enable Ventricular Safety Standby!

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Ventricular Safety Standby
64ms
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Ventricular Safety Standby
Crosstalk Ventricular Safety Pacing after 120 ms
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Ventricular Safety Standby
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Is Ventricular Safety Standby Pacing Present In
This Panel?
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Ventricular Safety Standby
Sensing in Crosstalk Detection Window Ventricular
Safety Pacing after 120 ms
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Ventricular Safety Standby
Blanking Period - No sensingVentricular Pacing
after programmed AV Interval
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Blanking period undersensing can be dangerous at
long AV intervals
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Crosstalk Ventricular Safety Standby
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• Special Timing Functions
• PMT
• PVC
• Crosstalk
• Auto Ventricular Blanking

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Auto Ventricular Blanking

• Maximizes the ventricular alert window.
• Minimizes inappropriate inhibition due to
  crosstalk.
• When crosstalk is present, ventricular blanking
  period automatically lengthens
• In the absence of crosstalk, ventricular blanking
  period remains short

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Auto Ventricular Blanking - Zephyr
Auto Ventricular Blanking - Programmability
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Auto Ventricular Blanking - Zephyr

• Programmable values
• Shipped setting is Auto

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Auto Ventricular Blanking - Zephyr

• AP - a 12 ms absolute blanking window begins.
• If ventricular activity (crosstalk) is sensed,
• a retriggerable 12 ms relative refractory
  window
• begins and can retrigger to a maximum of
• 52 ms.
• If no ventricular activity is sensed the
• ventricular channel enters an alert period.

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Auto Ventricular Blanking - Zephyr

• Crosstalk ends before 52 ms.
• No need for crosstalk detection window.
• Ventricular channel enters an alert period.

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Auto Ventricular Blanking - Zephyr

• Crosstalk reaches the maximum of 52 ms
• Ventricular Safety Standby will initiate a
  crosstalk detection window from 52 ms - 64 ms
• Normal Ventricular Safety Standby behavior will
  apply

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Auto Ventricular Blanking - Zephyr

• If there is sensing of constant ventricular
  events and the maximum of 52 ms is reached
• VSS will initiate a crosstalk detection window
  from 52 ms - 64 ms
• Normal Ventricular Safety Standby behavior will
  apply

VP
AP
120 ms VSS
Crosstalk Detection Window
Ventricular Crosstalk
Alert
12 ms
40 ms
12 ms
time
52 ms
64 ms
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Ventricular Blanking

• Programming EGM trigger
• High Ventricular Rate ? V Blanking to 12ms

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Auto Ventricular Blanking

• Auto Ventricular Blanking OFF
• Ventricular Blanking will auto program to 40 ms
  with the following
• Atrial output 6 Volts and higher
• Atrial pulse width 1.0 ms or longer

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