CRM 4,5 - Introduction to Pacemaker Timing and the NBG Pacing Code

Question 1

Describe the complex

Answer 1

-A paced, V sensed

Question 2

Describe the complex

Answer 2

-A sensed, V sensed
-A paced, V paced

Question 3

Describe the complex

Answer 3

-A sensed, V paced

Question 4

What is capture?

Answer 4

-Depolarisation following the pacing impulse

Question 5

What is sensing?

Answer 5

-When intrinsic complex is seen

Question 6

How do you convert interval to rate?

Answer 6

60bpm = 1000ms

Question 7

How do you convert rate to interval?

Answer 7

60bpm = 1000ms

Question 8

What is pacing interval?

Answer 8

-Time period between an event (paced or sensed) and the next event in the same chamber

Question 9

What is an active pacing interval?

Answer 9

-Active pacing intervals can be interrupted and restarted by a paced or sensed event

Question 10

What are refractory/blanking intervals?

Answer 10

-Refractory interval starts after paced/sensed beat
-Refractory interval categorises signals picked up
-Blanking period ignores signals picked up

Question 11

Lower rate interval/limit

Answer 11

Question 12

How does pacemaker create intracardiac electrogram (EGM)?

Answer 12

-Measured from tip/ring of pacing lead
-Only a few discrete cells at the point of contact create the sharp bipolar signal
-Pacemaker can only see this sharp signal, not surface ECG

Question 13

What are farfield signals?

Answer 13

-Signals from another cardiac chamber seen on electrogram

Question 14

What is atrial refractory?

Answer 14

-Notices the complex
-But does nothing

Question 15

What is retrograde

Answer 15

-Signals that fall into refractory periods can be termed retrograde

Question 16

Pacemaker code

Answer 16

Pace
Sense
Trigger/Inhibit

E.g. DOO - Dual pace, nothing, nothing

Question 17

What is this?

Answer 17

-AOO
-Atrial pacing spikes
-Exact interval between spikes

Question 18

What is this?

Answer 18

-VOO
-Ventricular pacing spikes
-Exact interval between spikes

Question 19

Issue with non-sensing modes

Answer 19

-VOO can cause VF (R on T)
-AOO can cause AF
-Uses up battery

Question 20

What is the interval that matters in AAO/VOO?

Answer 20

-Lower rate interval

Question 21

What is this?

Answer 21

DOO
-AV interval (PR interval)

Question 22

Features of DOO

Answer 22

-Atrial and ventricular spikes
-Lower rate limit and AV interval
-Intrinsic A and V not sensed
-Intrinsic signals do not trigger/inhibit

Question 23

What do refractory periods prevent?

Answer 23

-Double counting the same event
-Sensing the pacing stimulus, it’s after potential, and the evoked response
-In dual chamber devices, prevent PMT and cross-talk

Question 24

What is this?

Answer 24

AAI(R)
-Lower rate interval shortens at the end

Question 25

What is this?

Answer 25

VVI(R)

Question 26

What is this?

Answer 26

DDD -Paced QRS if there is no intrinsic beat during AV interval

Question 27

Other modes to consider

Answer 27

AAT - sees intrinsic atrial beat, triggers atrial paced beat VVT - sees intrinsic ventricular beat, triggers ventricular paced beat VDD - Only paces ventricle, senses both to set up AV interval DDI- A-sensed events inhibit atrial spike

Question 28

Pacemaker timing (could be in exam)

Answer 28

Question 29

What are the 2 types of refractory period?

Answer 29

Absolute/blanking - no signals 'seen' Relative/noise sampling - 'sees' and categorises signals but does not reset lower rate/refractory period

Question 30

Absolute refractory period Relative/noise sampling period Alert period

Answer 30

Question 31

Normal sinus node, complete AV block

Answer 31

-Let sinus node control atria -Dual chamber pacemaker -To sense P waves and create AV delay Or -Single chamber pacemaker with rate response

Question 32

How does VVIR work?

Answer 32

-Upper rate interval -Lower rate interval -If it doesn't see anything, it will pace -Makes interval shorter with activity

Question 33

Symptoms in VVI pacemaker

Answer 33

-Dizziness -Fatigue -SOB -Oedema -Hypotension -Due to loss of AV synchrony -V pace while atria is contracting

Question 34

Which devices have AV delay?

Answer 34

-Only dual chamber devices (AV synchronous pacing)

Question 35

What are the 2 types of AV delay?

Answer 35

pAV - paced AV interval sAV - sensed AV interval -Allows ventricular filling

Question 36

Why is pAV longer than sAV?

Answer 36

-Sensing starts in the middle of the P wave

Question 37

What is the VA interval?

Answer 37

-Interval from paced/sensed ventricular event to next atrial event

Question 38

What type of pacing does MTR apply to?

Answer 38

As Vp

Question 39

When does MTR start?

Answer 39

-After AV delay -When p/s V wave starts -Along with lower rate limit

Question 40

What is the MTR?

Answer 40

Maximum Tracking Rate -Fastest rate at which dual chamber pacemaker can pace ventricle after a sensed p wave

Question 41

If patient's sinus node is working (p waves), what type of pacemaker should you give?

Answer 41

-Dual chamber pacemaker