AMS Episodes

AMS = AUTOMATIC MODE SWITCH

by Gemita - 2020-08-14 14:49:01

Hello Mary,

AMS is a pacemaker algorithm which prevents tracking of atrial tachy arrhythmias like Atrial Fibrillation, Atrial Flutter, Atrial Tachycardia especially when they reach a certain speed and duration.   For example your EP (Electrophysiologist) might programme your pacemaker to mode switch when your heart rate reaches say 150 bpm and stays at this rate for a set period.  This is to prevent these high heart rates from getting through your AV Node to affect your ventricles which could be dangerous if the tachy arrhythmia is prolonged.  You could become extremely unstable very quickly.

The AMS switches the pacing to the right ventricle for the period of the atrial tachy arrhythmia, thereby ignoring the chaos in the right atrium, and then switches pacing back to the right atrium when the arrhythmia ceases.  It is really quite clever.  

Looking at your post, I see that you have a very high number of mode switches occurring, more than I am getting, and this tells me that you are probably going in and out of your tachy arrhythmias?  You say you had 108,238 AMS switches noted during your last pacemaker check?  Was this an annual figure or over a longer period ?

Yes I would recommend making an appointment to discuss your results with your cardiologist or EP since those high number of mode switches could be significant.  I got around 3,500 AMS episodes recorded over the last year which is, I believe, a fairly high burden but I am an in and out arrhythmia sufferer too !  With your high number of AMS episodes, it would be interesting to know the "total time you actually spent having arrhythmias".   They will have this information stored.  I would ask for a download of all your pacemaker data and you can study these results at your leisure. 

In case you want to read more detail, I attach a link

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1431592/

AMS

by AgentX86 - 2020-08-14 17:42:26

Gemita has it right, though I'd add that the "mode switch" would be between DDD (probably) and VVI. You can look up these pacing modes but as Gemita said, this change disconnects the ventricles from the atria so the ventricles no longer track the atria.

This loss of synchronization between the two chambers and can cause them to fight each other. Not only will your pace be capped but there is a loss of output because the atria are no longer helping the ventricles fill AND there may even be retrograde blood flow as the chambers pump against closed valves.

This isn't horrible and I'm sure you can feel it but it's a whole lot better than the ventricles tracking the atrial tachycardia. The AV node prevents this from happening naturally and pacemaker can't allow this either.

Yes 108,000 AMS switches is a LOT. I'm surprised that your EP didn't even mention this. Your PM's output voltage is quite high too. This will shorten its life. Their thought may be that there isn't a reason to replace the lead until the pacer's battery runs down so they only have to unzip you once.

Inappropriate mode switches ?

by Gemita - 2020-08-14 20:06:11

Thank you AgentX86 for filling in the gaps.  I was trying to keep it "simple" for Mary but pacemakers don't do simple, do they.

I wonder if Mary is getting inappropriate automatic mode switches to account for her very high AMS count unless it is a mistake and these excessive number of switches are certainly not going to help preserve battery life.

AMS

by WVMary - 2020-08-17 20:36:49

Thanks for the input.  I too am wondering if the automatic mode switches are inappropriate .  I do have increased heart rate when I walk in place several times a day and wonder if there is a connection. Thanks again to you both,