Single chamber modes
VVI
paces ventricle
senses ventricle
sensing inhibits pacing
Lower rate interval (LRI) consits of 2 parts
•Ventricular refractory period (VRP)
•Alert period/ventricular escape period (VEP)
A new LRI begins after each sensed or paced beat
Indications
•Symptomatic bradycardia of any etiology (AV block, SSS)
Contraindications
•Pacemaker syndrome
Pacemaker Syndrome involves congestive signs & symptoms associated with retrograde conduction during VVI pacing
Caused by
Loss of AV synchrony
•Can result in up to 50% decrease in stroke volume
•And/or lead to increase CI by 25-30%
•Leads to premature mitral valve closure
Continuous VA conduction (retrograde)
Compared to DDD, VVI can result in
•Neurological – presyncope
•Paced hypotension
•Weakness
•Chest pain
•Dyspnoea
•Cough
•Pulsation in neck (cannon A waves)
•Congestive HR
•Decreased cardiac output
•Hypertension when not pacing
Pacemaker syndrome prevalence
•Older studies say ~7-10%
•More recent studies show ~20%
•Comparison studies have shown up to 83%
VVT
paces ventricle
senses ventricle
sensing triggers pacing
Lower rate interval (LRI) – consists of 2 parts
•Ventricular refractory period (VRP)
•Alert period/ventricular escape period (VEP)
A new LRI begins after
each sensed or paced event
Indications
•When force pacing is desired, including fusion pacing (biventricular pacing when intrinsic rhythm is > LRI)
Contraindications
•Pacemaker syndrome
VOO - asynchronous
paces ventricle
no sensing
no sensing response
Lower rate interval (LRI)
Indications
•Temporary use when external interference may interrupt pacing
•Temporary use in case of lead fracture with a dependent patient
Contraindications
•Competitive intrinsic rhythm
•Long term use
OVO
no pacing
ventricular sensing
no sensing response
No pacing intervals
Indications
•Temporary setting when measuring sensing values
•If a device is required to be “turned off” (MRI setting/permanent pacing off)
Contraindications
•Pacing dependent
AAI
paces atrium
senses atrium
sensing inhibits pacing
Lower rate interval (LRI) – consists of 2 parts
•Atrial refractory period (ARP)
•Alert period/atrial escape period (AEP)
A new LRI begins after
each sensed or paced event
Indications
•Symptomatic bradycardia caused by SSS
Contraindications
•AV conduction disorders
•Chronic AF/AFl
AOO - asynchronous
paces atrium
no sensing
no sensing response
Lower rate interval (LRI)
Indications
•Temporary use when external interference may interrupt pacing
•Temporary use in case of lead fracture with a dependent patient
Contraindications
•Competitive intrinsic rhythm
•Long term use
OAO
no pacing
atrial sensing
no sensing response
No pacing interval
Indications
•Temporary setting when measuring sensing values
•If a device is required to be “turned off” (MRI setting/permanent pacing off)
Contraindications
•Pacing dependent
