Pacing & Defibrillation

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Dual chamber discrimination, atrial tachycardia

Patient

  • 63-year-old male with ischemic cardiomyopathy; implanted with Autogen triple-chamber defibrillator

 

Summary 1

  • episode diagnosed in the VT zone with atrial rate equal to ventricular rate
  • programmed discrimination: Onset/stability
  • therapy delivered (1 burst), due to the diagnosis of AF and stable rhythm

 

Tracé 1 EGM

  1. regular 1/1 tachycardia with atrial cycles classified as AF
  2. V-epsd marker (Gradl: gradual onset)
  3. end of duration; diagnosis of AF with stable ventricular rhythm
  4. ATP burst restores sinus rhythm

Tracé 2 EGM

  1. regular tachycardia 1/1 same as above
  2. V-epsd marker
  3. end of duration; inhibition of therapies because RID+.
  4. spontaneous termination in the ventricle (favors a diagnosis of atrial tachycardia)

Summary 2

  • episode diagnosed in the VT zone with atrial rate equal to ventricular rate
  • programmed discrimination: Rhythm ID
  • inhibition of therapy (RID+)

Take home message

  • these 2 traces illustrate the complexity of defibrillator programming; in the first trace, 1/1 atrial tachycardia is poorly discriminated by the Onset/Stability algorithm; in fact, the atrial rate exceeds the AF threshold and the rhythm is stable; the device suspects a possible dual tachycardia and delivers a burst of anti-tachycardia pacing which terminates the atrial arrhythmia; it is therefore an inappropriate therapy that has a beneficial effect; this type of 1/1 atrial tachycardia is almost systematically poorly discriminated by this algorithm, therefore a decision was made to switch to the Rhythm ID option, since the morphology criterion is theoretically effective in this type of tachycardia
  • the second plot shows that an identical episode of tachycardia (1/1 atrial tachycardia) that is then correctly discriminated in this patient with inhibition of therapies; the episode ends spontaneously, which raises the question of reprogramming the initial duration (lengthening it significantly) in the VT zone so as to maximize the probability of spontaneous termination without intervention of the discrimination algorithm; another option is to increase the lower limit of the VT zone (to 200 beats/minute for example), so as to avoid any overlap between the rates of this atrial tachycardia and the rates of possible VT.

On the second trace:

– the rhythm is stable with a diagnosis of AF: this would therefore lead to a diagnosis of VT if the Onset/Stability algorithm had been programmed

– QRS complexes are correlated (RID+), which explains why therapies are inhibited


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