Single-chamber AAI mode

Tracing
N° 4
Manufacturer Biotronik Device PM Field Pacing Modes
Patient

Same patient as in tracing 1.

Graph and trace

Tracing 4a: programming in AAI mode 50 beats/minute;

  1. permanent atrial sensing and inhibition of atrial pacing;

Tracing 4b: programming in AAI mode 60 beats/minute;

  1. permanent atrial pacing with preserved atrioventricular conduction but relatively long PR interval.
Comments

A single-chamber pacemaker operates in AAI mode when a single lead is positioned in the atrium; the AAI mode can also be programmed in a dual-chamber pacemaker. This tracing allows highlighting the main characteristics of this pacing mode:

  1. sensing and pacing of the atrium, inhibition due to a spontaneous atrial event; the preferred indication is therefore a pure sinus node dysfunction without ventricular conduction disorder. An AAI pacemaker allows limiting the number of implanted leads as well as ensuring a physiological rate at rest and during exercise after programming of the rate response while avoiding unnecessary ventricular pacing;
  2. absence of ventricular sensing or pacing. AAI single-chamber pacemakers or the programming of the AAI mode in a dual-chamber pacemaker are formally contraindicated in patients with permanent or paroxysmal atrioventricular conduction disorders. They should also be avoided in patients with vagal symptoms or carotid sinus syndrome.

A recent study has reported unfavorable results in the implantation of a single-chamber AAI pacemaker compared to the implantation of a dual-chamber pacemaker in patients with sinus dysfunction. Indeed, the rate of re-intervention is greater in patients implanted with an AAI with the need to add a ventricular lead as a result of the occurrence of an atrioventricular conduction disorder. Hence, the indications for the implantation of a single-chamber AAI pacemaker are nowadays relatively limited. 

In this patient, the prolonged post-atrial pacing PR interval is not propitious to the programming of AAI pacing in the long term.

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