Special Timing Functions PMT PVC Crosstalk Auto Ventricular Blanking

for internal use only


Special Timing Functions

• PMT

• PVC

• Crosstalk

• Auto Ventricular Blanking


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


PMT – Endless Loop Tachycardia






PMT - Conditions to be fulfilled

• Initiator

•Retrograde (VA) conduction

•VDD or DDD Pacemaker


PMT – Cycle Length

PMT cycle time=

VA conduction time +

programmed AV delay

(or Maximum Tracking Rate interval)



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


PMT – Initiation by PVC

PVCSurface ECG

Esophageal ECG

Retrograde P-waves

ASAP

VSVP

AP

VP

AS AS AS AS AS AS

VP VP VP VP VP VP VP


PMT – Initiation by PVC


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


PMT – Initiation by loss of atrial capture

Surface ECG

Retrograde P-waves

Esophageal ECG

AP

VP

AP

VP

AS AS AS AS AS AS

VP VP VP VP VP VP

AP

VP

AP

VP


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


PMT – Initiation by loss of atrial sensing

Surface ECG

Esophageal ECG

Retrograde P-waves

AP AS AS AS AS AS AS

VP VP VP VP VP VP VP

AS

VP

AS

VP

AS

VP



•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



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

sensor indicated rate


PMT Options SJM

•Off (nominal for Identity and Integrity)

•10 Beats > PMT

•Auto detect (nominal for Zephyr and Victory)

• No PMT options during AMS or Magnet Application


PMT Options SJM - 10 Beats > PMT

Detection•10 consecutive AS-VP events at a rate > 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


10 Beats > PMT

PVARP: 480ms

Atrial Alert Period 330ms


PMT Options SJM – Auto Detect

Detection• Rapid stable VP – AS interval

› Rapid: atrial rate > 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 < 100 ms› If VP – AS cycle is within 16 ms of average VP – AS cycle

PMT. Else Sinus Tachycardia



(VP-AS)1 (VP-AS)2

therefore:

sinus tachycardia

(VP-AS)2(VP-AS)1

(VP-AS)1 (VP-AS)2

(VP-AS)1 = (VP-AS)2

therefore:

PMT

AS - VP AS - VP(AS-VP) -

AS - VP AS - VP(AS-VP) -





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

pace


PMT Options SJM – Auto Detect and Response

Response• After 9th interval no ventricular response

• Atrial pulse 330 ms after retrograde P-wave


PMT Option Auto Detect

AVI: +50ms



• PMT

• PVC

• Crosstalk



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


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


PVC Options: + PVARP on PVC

After PVC Detection• PVARP extension to 480 ms

• Followed by atrial alert period of 330 ms


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


Atrial Pace on PVC

Extension of PVARP to 480

Atrial Alert Period of 330ms

330ms

DDD 60



• PMT

• PVC

• Crosstalk



What’s up Doc?


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


Crosstalk

Decrease atrial output?

Decrease ventricular sensitivity?

Prolong ventricular blanking?

Enable Ventricular Safety Standby!


Ventricular Safety StandbyB

lan

kin

g

Per

iod

Cro

ssta

lk

Det

ecti

on

W

ind

ow

64ms


Ventricular Safety Standby

Crosstalk

Ventricular Safety Pacing

after 120 ms

V EGM

sensitivity




Is Ventricular Safety Standby Pacing Present In This Panel?



Sensing in

Crosstalk Detection Window

Ventricular Safety Pacing

after 120 ms



Blanking Period - No sensing

Ventricular Pacing after

programmed AV Interval


Blanking period undersensing can be dangerous at long AV intervals


Crosstalk – Ventricular Safety Standby



• PMT

• PVC

• Crosstalk



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


Auto Ventricular Blanking - Zephyr

Auto Ventricular Blanking - Programmability



Programmable values

Shipped setting is Auto



• 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.

time

AP

12 ms

Absolute v. Blanking

52 ms

Maximum ventricular blanking interval

64 ms



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

R R

time

AP

Ventricular Crosstalk

No Crosstalk Detection Window

170 ms VP

40 ms

64 ms

Alert12 ms

52 ms

No Sensed Ventricular Event



• 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


time

AP

Crosstalk Detection Window

VP120 ms VSS

12 ms 40 ms Alert12 ms

64 ms

R R R R

52 ms



• 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


time

APCrosstalk

Detection Window

VP120 ms VSS

12 ms 40 ms Alert12 ms

64 ms52 ms


Ventricular Blanking

Programming EGM trigger

High Ventricular Rate V Blanking to 12ms


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


Special Timing Functions PMT PVC Crosstalk Auto Ventricular Blanking

Documents