Home /

Single Chamber Pacemaker Modes

Pacemaker single chamber modes

Pacemaker
Stimulation Modes
Single Chamber Pacemaker Modes
VOO Pacing
VVI Pacing
AOO Pacing
AAI Pacing

Pacemaker

PCM is a device implanted under the left clavicle
It serves to control heart rhythm

Mainly, it protects the heart from symptomatic bradycardia

It can have 1, 2, or 3 leads

Each lead is introduced into a different heart chamber:

Right atrium, right ventricle, left ventricle

Through the leads, the pacemaker can

Sense the electrical activity of the chamber (sensing)
Stimulate the respective chamber (pacing)

Stimulation Modes

Each pacemaker is classified according to the NBG code (table below)

Posi- tion	I	II	III	IV	V
	Cham- ber(s) Paced	Cham- ber(s) Sensed	Response to Sensing	Rate Modula- tion	Multisite Pacing
	O = Off	O = Off	O = Off	O = Off	O = Off
	A = Atrium	A = Atrium	T = Triggered	R = Rate Modula- tion	A = Atrium
	V = Ventricle	V = Ventricle	I = Inhibited		V = Ventricle
	D = Dual (A+V)	D = Dual (A+V)	D = Dual (T+I)		D = Dual (A+V)

Single Chamber Pacemaker Modes

Pacemaker single chamber mode (atrial lead)

Pacemaker single chamber mode (ventricular lead)

Single chamber pacemaker has only 1 lead

In the right atrium or the right ventricle

Single chamber modes are:

VOO
VVI
AOO
AAI

VOO Pacing

V - Ventricle pacing
O - Sensing is off
O - Response to sensing is off
This is asynchronous pacing

The pacemaker has its own programmed rate, regardless of the heart's intrinsic activity

Pacemaker single chamber VOO mode (ventricular lead)

VOO Pacing (Asynchronous Ventricular Pacing)

Pacing rate of 60/min. (1000ms) (red arrows)
2nd and 5th QRS are intrinsic QRS complexes (green arrows)

Followed by pacing in the refractory period
Myocardium is non-excitable during the refractory period

F is a fusion beat

The QRS complex is created by 2 impulses
From the pacemaker and from a sinus impulse

Second-to-last QRS is a spontaneous ventricular extrasystole
VOO pacing behaves like parasystole

The heart has 2 autonomous pacemakers:
Its intrinsic sinus rhythm
The ventricular rhythm from the pacemaker

VVI Pacing

V - Ventricle pacing
V - Ventricle sensing
I - Positive sensing inhibits pacing
The pacemaker senses the intrinsic electrical activity of the chamber

Intrinsic electrical activity "turns off" the pacing

Pacemaker single chamber VVI mode (ventricular lead)

VVI Pacing

The pacemaker is programmed at a rate of 60/min. (1000ms - 5 squares)

Sensing detects each QRS complex
If no intrinsic QRS occurs within 1000ms from the previous QRS, pacing is activated

1st and 2nd QRS are intrinsic QRS complexes (green arrows)

The interval between them is 800ms

After the 2nd QRS, no intrinsic QRS occurred within 1000ms, so pacing was activated (red arrow)
5th QRS is a ventricular extrasystole, followed by pacing again after 1000ms

AOO Pacing

A - Atrial pacing
O - Sensing is off
O - Response to sensing is off
This is asynchronous atrial pacing

The pacemaker has a preset frequency, regardless of intrinsic atrial activity

Pacemaker single chamber AOO mode (atrial lead)

AOO Pacing (Asynchronous Atrial Pacing)

Pacing rate of 70/min. (857ms) (red arrows)
3rd, 4th, and 5th QRS (green arrows) are intrinsic sinus QRS complexes

Intrinsic atrial activity does not inhibit pacing

AAI Pacing

A - Atrial pacing
A - Atrial sensing
I - Positive sensing inhibits pacing
The pacemaker senses intrinsic atrial activity

Intrinsic electrical activity "turns off" pacing

Pacemaker single chamber AAI mode (atrial lead)

AAI Pacing

The pacemaker is programmed to a rate of 70/min. (857ms)

Sensing registers each P wave
If no intrinsic P wave occurs within 857ms from the previous P wave, pacing is activated

The 1st and 2nd P waves are intrinsic P waves (green arrows)

The interval between them is 850ms

No intrinsic P wave occurs within 857ms after the 2nd P wave, so pacing is activated (red arrow)

Atrial pacing activates if no intrinsic P wave occurs within 857ms

Sources

ECG from Basics to Essentials Step by Step
litfl.com
ecgwaves.com
metealpaslan.com
medmastery.com
uptodate.com
ecgpedia.org
wikipedia.org
Strong Medicine
Understanding Pacemakers

Home /

Single Chamber Pacemaker Modes

Pacemaker single chamber modes

Pacemaker
Stimulation Modes
Single Chamber Pacemaker Modes
VOO Pacing
VVI Pacing
AOO Pacing
AAI Pacing

Pacemaker

PCM is a device implanted under the left clavicle
It serves to control heart rhythm

Mainly, it protects the heart from symptomatic bradycardia

It can have 1, 2, or 3 leads

Each lead is introduced into a different heart chamber:

Right atrium, right ventricle, left ventricle

Through the leads, the pacemaker can

Sense the electrical activity of the chamber (sensing)
Stimulate the respective chamber (pacing)

Stimulation Modes

Each pacemaker is classified according to the NBG code (table below)

Position	I	II	III	IV	V
	Chamber(s) Paced	Chamber(s) Sensed	Response to Sensing	Rate Modulation	Multisite Pacing
	O = Off	O = Off	O = Off	O = Off	O = Off
	A = Atrium	A = Atrium	T = Triggered	R = Rate Modulation	A = Atrium
	V = Ventricle	V = Ventricle	I = Inhibited		V = Ventricle
	D = Dual (A+V)	D = Dual (A+V)	D = Dual (T+I)		D = Dual (A+V)

Single Chamber Pacemaker Modes

Single chamber pacemaker has only 1 lead

In the right atrium or the right ventricle

Single chamber modes are:

VOO
VVI
AOO
AAI

VOO Pacing

V - Ventricle pacing
O - Sensing is off
O - Response to sensing is off
This is asynchronous pacing

The pacemaker has its own programmed rate, regardless of the heart's intrinsic activity

VOO Pacing (Asynchronous Ventricular Pacing)

Pacing rate of 60/min. (1000ms) (red arrows)
2nd and 5th QRS are intrinsic QRS complexes (green arrows)

Followed by pacing in the refractory period
Myocardium is non-excitable during the refractory period

F is a fusion beat

The QRS complex is created by 2 impulses
From the pacemaker and from a sinus impulse

Second-to-last QRS is a spontaneous ventricular extrasystole
VOO pacing behaves like parasystole

The heart has 2 autonomous pacemakers:
Its intrinsic sinus rhythm
The ventricular rhythm from the pacemaker

VVI Pacing

V - Ventricle pacing
V - Ventricle sensing
I - Positive sensing inhibits pacing
The pacemaker senses the intrinsic electrical activity of the chamber

Intrinsic electrical activity "turns off" the pacing

VVI Pacing

The pacemaker is programmed at a rate of 60/min. (1000ms - 5 squares)

Sensing detects each QRS complex
If no intrinsic QRS occurs within 1000ms from the previous QRS, pacing is activated

1st and 2nd QRS are intrinsic QRS complexes (green arrows)

The interval between them is 800ms

After the 2nd QRS, no intrinsic QRS occurred within 1000ms, so pacing was activated (red arrow)
5th QRS is a ventricular extrasystole, followed by pacing again after 1000ms

AOO Pacing

A - Atrial pacing
O - Sensing is off
O - Response to sensing is off
This is asynchronous atrial pacing

The pacemaker has a preset frequency, regardless of intrinsic atrial activity

AOO Pacing (Asynchronous Atrial Pacing)

Pacing rate of 70/min. (857ms) (red arrows)
3rd, 4th, and 5th QRS (green arrows) are intrinsic sinus QRS complexes

Intrinsic atrial activity does not inhibit pacing

AAI Pacing

A - Atrial pacing
A - Atrial sensing
I - Positive sensing inhibits pacing
The pacemaker senses intrinsic atrial activity

Intrinsic electrical activity "turns off" pacing

AAI Pacing

The pacemaker is programmed to a rate of 70/min. (857ms)

Sensing registers each P wave
If no intrinsic P wave occurs within 857ms from the previous P wave, pacing is activated

The 1st and 2nd P waves are intrinsic P waves (green arrows)

The interval between them is 850ms

No intrinsic P wave occurs within 857ms after the 2nd P wave, so pacing is activated (red arrow)

Atrial pacing activates if no intrinsic P wave occurs within 857ms

Sources

ECG from Basics to Essentials Step by Step
litfl.com
ecgwaves.com
metealpaslan.com
medmastery.com
uptodate.com
ecgpedia.org
wikipedia.org
Strong Medicine
Understanding Pacemakers