User Manual Part 1

PACING T HERAPIES

BASIC PARAMETERS

5-5

During PES, Manual Burst pacing, and ATP, runaway protection is temporarily

suspended to allow for high-rate pacing.

Maximum Tracking Rate (MTR)

TheMTRisthemaximumrateatwhichthepacedventricularratetracks1:1

with nonrefractory sensed atrial events. MTR applies to atrial synchronous

pacing modes, namely DDD(R) and VDD(R).

The following are considerations for programming the MTR:

• Interactive limits ("Lower Rate Limit (LRL)" on page 5-4).

• When the sensed atrial rate is between the programmed LRL and MTR, 1:1

ventricular pacing will occur in the absence of a sensed ventricular event

within the program med AV Dela y. If the se nsed atrial rate exceeds the MTR,

the pulse generator might begin a Wenckebach-like behavior to prevent

the paced ventricular rate from exceeding the MTR. This Wenckebach-like

behavior is characterized by a progressive lengthening of the AV delay

until an occasional P-wave is not tracked because it falls into the PVARP.

This results in an occasional loss of 1 :1 tracking as the pulse generator

synchronizes its paced ventricu lar rate to the next sensed P-wave. Should

the sensed atrial rate continue to increase further above the MTR, the ratio

of se nsed atrial ev ents to sequentially paced ventricular events be comes

lower until, eventually, 2:1 block results (e.g., 5:4, 4:3, 3:2, and ﬁnally 2:1).

• The PRM will not allow you to program an MTR interval shorter than TARP

(AV Delay + PVARP = TARP). If TARP is less than the interval of the

programmed MTR, then the pulse generator ’s Wenckebach-like behavior

limits the ventricular pa cin g rate to th e MTR. With TARP, the PRM does not

consider the AV Search AV Delay. If AV Search is on, Wenckebach-like

behavior may occur at rates lower than the MTR.

• Rapid changes in the paced ventricular rate (e.g., Wenckebach-like, 2:1

block) caused by sensed atrial rates above the MTR may be dampened or

eliminated by the implementation of any of the following:

–AFR

–ATR

– Rate Smoothing parameters and sensor input

–VRR

- DRAFT -