How are pacemakers programmed?

Updated: Oct 11, 2019
  • Author: Daniel M Beyerbach, MD, PhD; Chief Editor: Jeffrey N Rottman, MD  more...
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Modern pacemakers have multiple functions. The simplest settings are VVI and AAI. The VVI mode senses and paces the ventricle and is inhibited by a sensed ventricular event. Alternatively, the AAI mode senses and paces in the atrium, and each sensed event triggers the generator to fire within the P wave. (See the image below.)

100% ventricular paced rhythm. 100% ventricular paced rhythm.

The most common setting, the DDD mode, denotes that both chambers are capable of being sensed and paced. This requires two functioning leads, one in the atrium and the other in the ventricle. On the electrocardiogram (ECG), if both atrium and ventricle are being paced, there will be a pacing artifact before the P wave and preceding the QRS. The first pacing artifact indicates the atrial depolarization, and the second indicates the initiation of the QRS complex. Given that one of the leads is in the right ventricle, a left bundle-branch pattern may be evident on ECG.

Note that a 2-wired system does not necessarily need to be in DDD mode, since the atrial or ventricular leads can be programmed off. Additionally, single tripolar lead systems are available that can sense atrial impulses and either sense or pace the ventricle. Thus, this system provides for atrial tracking without the capability of atrial pacing and can be used in patients with AV block and normal sinus node function.

Pacemaker programming can be performed noninvasively by an electrophysiology technician or cardiologist. Because of the myriad of pacemaker types, patients should carry a card with them providing information about their particular model. Most pacemaker generators have an x-ray code that can be seen on a chest radiograph; however, the chest radiography may need to be zoomed onto the pacemaker generator for better resolution. The markings, along with the shape of the generator, may assist with deciphering the manufacturer of the generator and pacemaker battery.

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