Read the full journal at http://arrhythmiagr.com. Code: agr-00008-14-f01-01

1. 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: ………………………….

2. 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

3. 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

4. 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.

5. Questions
 Can the persistent symptoms be due to the
pacing system?
 How might this be evaluated?

6. Evaluation
 The excellent capture and sensing thresholds
make an early lead problem unlikely
 The baseline rhythm:

7. 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

8. 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

9. AAI pacing at 100 bpm

10. AAI pacing at 120 bpm

11. AAI pacing at 140 bpm

12. 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

13. 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

14. 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

15. AAI Pacing at 125 bpm
 2:1 Second Degree AV block develops

16. 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

17. 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.