Paul A. Levine MD, FHRS, FACC, CCDS

Professor of Medicine

Loma Linda University School of Medicine

Clinical Associate Professor of Medicine

University of California, Los Angeles

AV Nodal Conduction System

Stress Test

Based on: Levine PA, The AV Nodal Conduction System Stress Test, Arrhythmia

Grand Rounds, 2014: 1: ………………………….

Clinical History

63 year old male presents with repeated weak

spells and pre-syncope

Following diagnosis of sinus node

dysfunction, implantation of a dual chamber

pacing system is recommended and proceeds

in an uncomplicated manner.

The implanted pulse generator is Medtronic

Advisa™ A2DR01

Managed Ventricular Pacing

(MVP):

MVP is the default pacing mode in the Medtronic

pacemakers

It provides functional single chamber atrial pacing

in the absence of AV block

If AV block develops, there needs to be 2:1 second

degree AV block for four cycles or higher levels of

AV block before it will disable functional single

chamber atrial pacing in favor of the DDD mode

After a period of time in the DDD mode, the

algorithm withholds the ventricular output to

determine if AV block persists or has resolved

Clinical History (cont)

The patient reports that the pre-syncopal

episodes have resolved but some weak spells

persist.

At follow-up, capture and sensing thresholds

are stable, there have been no

tachyarrhythmias and there is only 1%

ventricular pacing with the system in the MVP

mode.

Questions

Can the persistent symptoms be due to the

pacing system?

How might this be evaluated?

Evaluation

The excellent capture and sensing thresholds

make an early lead problem unlikely

The baseline rhythm:

Evaluation (cont):

There is a mild first degree AV block but this

would not be expected to be symptomatic

Could there be intermittently higher levels of

AV block?

How might intermittent AV block be

evaluated?

Holter or Event Monitor

Formal EP study assessing AV conduction

Bedside AV Nodal Conduction System Stress

Test

AV Nodal Conduction System Stress test

To determine if it is safe to program the

pacemaker to the fixed or functional single

chamber atrial pacing mode (AAI), it is necessary

to assess the status of the AV conduction system.

AV Nodal Conduction Stress Test Pace AAI at progressively higher rates

Intact AV conduction to atrial paced rates of > 120 ppm

Since this test is performed at rest, there will not

be the increased circulating catecholamine levels

that are present during physical activity Hence Wenckebach AV block may occur at atrial paced rates

that would not occur during physical exercise

AAI pacing at 100 bpm

AAI pacing at 120 bpm

AAI pacing at 140 bpm

Question

What is the cause of the pause during AAI

pacing at 140 ppm?

A. Wenckebach 2nd degree AV block

B. First degree AV block

C. First degree AV block with FFRW sensing

D. Atrial oversensing

Question 4

What is the cause of the pause during AAI

pacing at 140 ppm?

A. Wenckebach 2nd degree AV block

B. First degree AV block

C. First degree AV block with FFRW sensing

D. Atrial oversensing

Programming High Rates in the

Medtronic Pacemakers

Program to the AAI mode and a high rate

When evaluation completed, need to reprogram

the pacemaker to the desired parameters

Utilize the Capture Threshold test

This is performed in a temporary mode such

that when ended, the mode and rate go back to

the baseline

In DDD mode, highest allowed rate is 120 bpm

In AAI mode, highest allowed rate is 175 bpm

AAI Pacing at 125 bpm

2:1 Second Degree AV block develops

Management

Intermittent low grade AV block could explain

his continued weak spells

Disable MVP mode in favor of DDDR

combined with the Search AV+ hysteresis

algorithm

Reassess in 1 to 3 months

If symptoms resolved, patient has intermittent

AV block in addition to sinus node dysfunction

If symptoms persist, need to continue to

evaluate

Management

When ever programming to the fixed AAI

mode or the functional AAI mode, it is prudent

to assess the status of the AV nodal

conduction system at each follow-up visit.

This patient called the office two weeks after

having been seen and his pacemaker

programmed to report total resolution of his

intermittent weak spells.