Wenckebach behavior during exertion

N° 28
Manufacturer Medtronic Device PM Field Programming for exercise

Same patient as in the preceding tracing; change in programming with a shortening of the PVARP value, programming of an adjustable AV delay; new exercise test (flexions) with attenuation of the sensation of discomfort relative to the previous tracing.

Graph and trace

The first line corresponds to lead II, the second line to the atrial EGM with the superimposed markers and the third line to lead I;

  1. AS-VP interval with programmed AV delay;
  2. AS-VP interval with prolongation of the AV delay so as to meet the 120 beats/minute maximal tracking rate;
  3. Wenckebach behavior with prolongation of the AV delay;
  4. blocked P wave; indeed, the wave falls within the PVARP and induces neither AV delay nor ventricular pacing;
  5. resumption of AV synchrony with short AV delay;
  6. continuation of Wenckebach behavior (4/3).

The exercise test is an important component of the follow-up of implanted pacemaker recipients especially in the presence of symptoms. Ideally, it should be performed while analyzing the EGM during the exercise using the programmer in order to detect a possible dysfunction and allow real-time reprogramming based on the observations made. The exercise performed can be a simple walk to reproduce efforts of everyday life. Repetitive flexions mimic a more vigorous effort. These two types of exercise tests are of practical interest since they can be carried out at the time of the consultation. A standard bicycle exercise test offers the advantage of continuous 12-lead electrocardiographic monitoring. Another value of the exercise test is the verification of the effectiveness of a programming change. In this patient, the shortening of the AV delay and of the PVARP allowed a relocation of the 2/1 point to a more suitable rate (> 220 beats/minute). On the other hand, maintaining a maximal tracking rate at 120 beats per minute explains the Wenckebach behavior observed on this tracing. The sensed AV delay is prolonged from one interval to another in order to prevent the maximum synchronous rate from being exceeded. In this patient, the Wenckebach function is of the 4/3 type (4 P waves for 3 ventricular pacings). An increase in sinus rate would increase the proportion of blocked P waves. There is no valid reason to curb the maximal tracking heart rate in this young active patient free of structural heart disease. A reprogramming of the maximum synchronous rate to 180 beats per minute enabled a consistent atrial tracking over the entire rate range of this patient at rest as well as during maximal effort.  

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