Pacemaker Nomenclature

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PACEMAKER NOMENCLATURE –

NASPE/BPEG Revised in 2002 NBG Pacemaker Code
Position I Position II Position III Position IV Position V

(Chamber Paced) (Chamber Sensed) (Response to Sensed Event) (Programmability, (Multisite Pacing)
O = none O = none O = none Rate Modulation) O = none
A = atrium A = atrium I = inhibited A = atrium
V = ventricle V = ventricle T = triggered O = none V = ventricle

D = dual (A + V) D = dual (A + V) D = dual (T + I) R = rate moduation D = dual (A + V)



The first two positions of this code (Chamber Paced and Sensed) are relatively
straightforward. The third position is the most confusing. The most frequently used programs are
the DDD (dual chamber pacing and sensing, both triggered and inhibited mode), VVI (for single
chamber, ventricular pacing in the inhibited mode), VDD (ventricular pacing with atrial tracking),
and DDI (dual chamber pacing and sensing, but inhibited mode only).

The third position is described as follows:
D - (dual): In DDD pacemakers, atrial pacing is in the inhibited mode (the pacing device
will emit an atrial pulse if the atrium does not contract). In DDD and VDD pacemakers,
once an atrial event has occurred (whether paced or native) the device will ensure that an
ventricular event follows.

I - (inhibited): The device will pulse to the appropriate chamber unless it detects intrinsic
electrical activity. In the DDI program, AV synchrony is provided only when the atrial
chamber is paced. If on the other hand if intrinsic atrial activity is present, then no AV
synchrony is provided by the pacemaker.

T - (triggered): Triggered mode is only used when the device is being tested. The pacing
device will emit a pulse only in response to a sensed event.

The VDD pacemaker is used for AV nodal dysfunction but intact and appropriate sinus
node behavior. DDI is rarely used as the primary mode of pacing. The DDI pacer is used for a
patient with a dual-chamber pacemaker that has episodes of paroxysmal atrial fibrillation. DDI
prevents high ventricular rates. Some DDD pacemakers are programmed to enter the DDI mode
when high atrial rates occur.

The fourth position, rate modulation, increases the patient’s heart rate in response to
“patient exercise”. A number of mechanisms (vibration, respiration, and pressure) are used to
detect “patient exercise”. As the exercise wanes, the sensor indicated rate returns to the
programmed mode.

The fifth position describes multisite pacing functionality. Atrial multisite pacing is being
investigated as way to prevent atrial fibrillation. Ventricular multisite pacing is a treatment for
pacing a patient with dilated cardiomyopathy.

There are four types of pacemakers: asynchronous, single-chamber synchronous,
double-chamber AV sequential, and programmable.

• Asynchronous or fixed-rate (AOO, VOO, DOO) – discharge at a preset rate that is
independent of the inherent heart rate.

• Single-chamber synchronous or demand (AAI, VVI) – discharge at a preset rate only
when the spontaneous heart rate drops below the preset rate.

• Dual-chamber AV sequential pacing (VDD, DVI, DDD) – usually uses two electrodes, one
in the atrial appendage and one in the right ventricular apex. The atrium is stimulated to
contract first, then after an adjustable PR interval, the ventricle is stimulated.

• Programmable pacemakers – pacing rate, pulse duration, voltage output, and R-wave
sensitivity are the most common programmable functions.

My chart didnt work out so well so I included a word file. One type of question I have come across related to this is that they give you an EKG tracing and ask you to determine which type of pacemaker the patient has. I have also included that in the word file as I cant seem to get it to paste in the thread.

Originally Posted by usnavdoc

The third position is described as follows:
D - (dual): In DDD pacemakers, atrial pacing is in the inhibited mode (the pacing device
will emit an atrial pulse if the atrium does not contract). In DDD and VDD pacemakers,
once an atrial event has occurred (whether paced or native) the device will ensure that an
atrial event follows.

Great overview! Thank you! Did you mean (in the last sentence above) "... the device will ensure that a ventricular event follows"?

For me, the third position was always hardest to understand, until I realized that it describes the reaction of the pacer to the heart, not the other way round. I.e., you have to ask: does the pacemaker get triggered or inhibited or both by what the heart is doing?

Originally Posted by Freibi

Great overview! Thank you! Did you mean (in the last sentence above) "... the device will ensure that a ventricular event follows"?

For me, the third position was always hardest to understand, until I realized that it describes the reaction of the pacer to the heart, not the other way round. I.e., you have to ask: does the pacemaker get triggered or inhibited or both by what the heart is doing?

Yeah thanks for the corection. I always had trouble with the third position as well.