Wenckebach behavior during exercise Copy Copy


  • same patient than previous tracing
  • programming of rate adaptive AV delay and PRAPV auto


  • AS-VP with the prescribed AV delay (70 ms at peak exercise)
  • progressive prolongation of the AV delay in order to maintain the heart rate at the maximum rate limit
  • marked prolongation of the AV delay
  • P wave falling inside the post ventricular atrial blanking (Ab) and therefore not followed by ventricular pacing
  • dropped P wave
  • Wenckebach behavior 8/7: progressive prolongation of the AV delay and 1 dropped P wave every 8 P waves


  • this tracing illustrates a case of Wenckebach behavior during exercise
  • when the intrinsic atrial activity is faster than the programmed maximal tracking rate, the device has to wait until the upper rate interval has timed out before it can release a ventricular stimulus
  • the AV delay has to be extended to deliver ventricular pacing at the completion of the upper rate interval
  • if the A-V interval is further extended on repeated cycles, the VA interval is reduced in parallel and eventually a P wave will fall in the PVARP and will not initiate an AV delay (dropped P wave) and a pause will occur
  • the following P wave is outside all refractory periods and initiates a new programmed AV delay
  • this pattern is repeated for as long as the sinus rate remains above the programmed maximum tracking rate
  • missing beats occur less frequently when the sinus rate is only slightly higher than the maximum tracking rate and more frequently when the sinus rate well exceeds the maximum tracking rate
  • once the sinus rate falls below the maximum tracking rate, the 1:1 AV association is restored
  • Wenckebach behavior can be defined by the rate at which the missing beat occurs and by the ratio of sensed atrial events over paced ventricular events (e.g., 8/7, 7/6, 6/5 or 3/2)
  • the Wenckebach behavior is most often less symptomatic than the 2:1 behavior although it must be avoided by setting a sufficiently high maximum tracking rate
  • increasing the maximal tracking rate solved the problem