Timing cycles Flashcards
What 2 schemes does dual chamber timing rest on?
A-A timing and V-V timing
In A-A timing, what is constant and what adjusts?
A-A timing is constant. V-A adjusts
In V-V timing, what is constant and what adjusts?
V-A timing is constant; A-A adjusts. Atrial rate (A-A) varies with intrinsic ventricular conduction
In DDD, what timing does an AP trigger?
Lower rate timer and AV delay timer (PAV)
What happens when PAV expires?
VP
What does an AS inhibit and trigger?
Inhibits the lower rate timer and triggers a sensed AV delay (SAV)
What happens when an AS expires?
Hasn’t been inhibited by a VS in the timing cycle, so it VP
What can inhibit a SAV?
VS
What is the ventricular safety pacing window (VSP) and when does it occur?
110ms after a AP
What is PVAB?
Post-ventricular atrial blanking
What causes PVAB to start?
VS or VP
What is PVARP?
Post-ventricular atrial refractory period
What does the existence of PVARP avoid?
Tracking of retrograde P-waves or PACs
When a far-field signal from the ventricular channel is being sensed in the atrial channel (far field R waves), what timing interval can be changed to avoid this?
PAVB
Which timing interval avoids tracking of retrograde P-waves or PACs?
PVARP
