Alternating atrial sensed and pace events

Tracing N° 1
Medtronic Devices: CRT Field: Nominal parameters

47 years old man, implanted with a triple chamber defibrillator Viva XT CRT-D for dilated cardiomyopathy with left bundle branch block; 3 months – routine - follow-up after implantation (DDD 70 bpm) ; 

Graph and trace


  1. atrial stimulation and biventricular stimulation (AP-BV) ;
  2. atrial sensed event and biventricular stimulation (AS-BV) ;
  3. persistent alternating atrial paced and sensed events;
  4. modification of the programing: DDD 60 bpm;
  5. permanent atrial detection and biventricular stimulation ;

In the absence of manifest sinus node dysfunction, it is preferable to promote spontaneous atrial activity by programing a relatively low minimal HR. In this patient, programming the minimal HR at 70 bpm induced a competition and alternation between the spontaneous atrial rhythm and the atrial pacing. Slowing the minimum frequency yielded a permanent atrial sensing at rest as during exercise which allows 1) to limit energy consumption and save battery 2) maintain a physiological atrial activation and reduce the atrial activation time. However, the effect on the potential occurrence of an atrial arrhythmia remains more controversial.

Theoritical features / Basic concepts

Basic parameters programming Minimal rate and pacing mode Upper tracking rate Rate reponsive mode Switch mode Atrial and ventricular sensing Blanking periods PVARP Ventriculo-atrial crosstalk prevention BASIC PARAMETERS PROGRAMMING The first goals of the basic CRT programming are to maintain a permanent biventricular capture and to optimize the patient hemodynamic. CRT recipients may present various form of underlying disease. Therefore CRT optimization should be tailored to the patient characteristics. CRT programming should also take into account the need for detecting and treating ventricular arrhythmias.  Minimal rate and pacing mode  Tuning the pacing basic interval will impact the percentage of atrial pacing. The left atrium is the only cavity that cannot be stimulated directly with...