Upper rate behaviour in dual chamber pacemaker

Dr Shreetal Rajan NairSenior resident , Department of Cardiology

MCH, Calicut.

DDD pacemaker- 4 rhythm scenarios

Dual Chamber Timing Cycle

• Lower rate interval (LRI)• Upper rate interval (URI) – Maximum tracking rate (MTR)

– Maximum sensor rate • AV and VA interval• Refractory period• Blanking period

Dual-chamber Timing Intervals

AV Interval

TARPVA Interval

LRI

A-BlankingPVARPV-Blanking

URI/MTR

VRP

Ap Vp Ap Vp Ap Vp

Upper rate behavior refers to how a dual-chamber pacemaker will behave when the atrial rate exceeds the programmed maximum tracking rate

There are three types of upper rate behavior

1:1 Tracking

Pacemaker Wenckebach

2:1 Block

The key to upper rate behavior is in the atrium

Observed only when the device is tracking intrinsic P waves (A sense/V pace)

Upper rate behavior

Normal 1:1 tracking

Pacemaker Wenckebach (PSEUDOWENCKEBACH)

W

As Vp As Vp

MAXIMUM TRACKING RATE

TARP

PVARP

AV

TARP

PVARP

AV

Upper Rate Pacing CharacteristicsWenckebach (4:3 Block)

As Vp As Vp As Vp (As) As Vp As Vp As Vp

TARP

AV Delay

VA Interval

MTR

Upper Rate Pacing Characteristics

As Vp (As) As Vp As Vp As Vp(As) (As) (As)

TARPAV DelayVA Interval

MTRLRI

2:1 Block

2:1 Block

AV

PVARP

TARP

MAXIMUM TRACKING RATE

AV

PVARP

TARP

As Vp (As) As Vp

2:1 Rate = 60,000 / TARP

Upper Rate Pacing Characteristics

Upper Rate Pacing Characteristics

1:1

Wenckebach

2:1 BlockTARP

MTR

LRI

SinusRate

Upper Rate Behavior is determined by TARP and MTR

How to deal with this?

Solution In young patients, the upper rate of the

pacemaker to be programmed to faster rates corrected for the patient's age to prevent Wenckebach behavior of the pacemaker during exercise.

Programming dynamic AV interval and dynamic PVARP allows the TARP to be shorter at higher pacing rates and avoid sudden slowing of ventricular pacing rates.

Sensor driven pacing : a separately programmable sensor rate allows the pacemaker to continue to pace at the sensor-driven rate during exercise

Dynamic AVI and PVARP

Programmed AV Delay shortens with increasing rate

Allows programming a higher MTR for higher 1:1 P-synchronous tracking

Dynamic AVI and PVARP

AV Delay + PVARP = TARP

65 ms

300 ms 365 ms (164 ppm)

130 ms

300 ms 430 ms (139 ppm)

200 ms

300 ms 500 ms (120 ppm)

Effects of Shorter AV Delay

Dynamic AVI and PVARP

Rate = 65 ppm AV Delay ~ 180 ms Rate to 135 ppm

AV Delay

~ 80ms

Rate-responsive PacingSensor driven (DDDR) pacing promotes a

more regular rhythm if the sinus rate exceeds the MTR. It is not dependent on the PVARP

DDD - Wenckebach

DDDR

Thank you