PMT

Question 1

PMT requires what 4 things to occur?

Answer 1

1. Dual chamber PPM
2. Retrograde conduction
3. Triggering event eg: loss of atrial capture, SVE, VE
4. PVARP is shorter than the VA interval (conduction occurs outside PVARP)

Question 2

How do most PMT algorithms work?

Answer 2

Extending PVARP. This causes the retrograde atrial activity to not be sensed as it falls in PVARP.

Question 3

What determines how fast can PMTs get?

Answer 3

Max track rate (MTR); normally around 120bpm

Question 4

How does the loss of atrial capture cause a PMT?

Answer 4

Because atria didn’t capture/ depolarise, they are not in refractory after the ventricular paced event, and are therefore able to depolarise when the retrograde conduction occurs. Normally this would be too soon and the atria would be in refractory.

Question 5

What is PMT?

Answer 5

The PPM senses and tracks retrograde conduction, which causes inappropriately fast pacing