Automatic mode switching (AMS) in atrial fibrillation

In Feb. 2022, I had a checkup and my AMS rate was 9 events.  In July 2022, I had a software update for my PM and my AMS events were 565.  I know this is mostly for dual-chamber pacemakers like mine by Abbot that is pacing me 100% of the time.  Can someone put in layman's terms what AMS events are telling me?  My home monitor sent an alert to the hospital over the events, so is this something I should be concerned with?


AMS - automatic mode switch

by Gemita - 2022-08-22 01:14:58

Stache, AMS is the automatic switching of pacemaker modes to prevent the tracking of an atrial tachyarrhythmia for the duration of the arrhythmia.  The mode automatically switches back to its former mode setting at cessation of the atrial tachy arrhythmia.  This pacemaker function prevents the fast atrial rate being picked up by atrial sensing and then pushing the ventricles too fast which would of course be dangerous, especially if the arrhythmia was long lasting.  So AMS is like a safety device.  Mode switch will also help to control our symptoms which can only be a good thing.

Should you be concerned?  Yes and no.  Yes in that any increase in mode switching tells your doctors that your atrial tachy arrhythmias are becoming more frequent, that your heart rates during episodes have exceeded the parameters set by your EP (say above 165 bpm) to trigger a mode switch.  This would suggest that your heart rate and arrhythmia control may need to be better managed.  No in that if you have frequent, short bursts of atrial tachy arrhythmias like me, your doctor might not be too concerned.  While short in and out episodes can be destabilising at times, because episodes start and stop on their own, without intervention, doctors may not be too concerned.   For example, my % time in AF continues to be extremely low despite all my mode switches and has been like this for years which does surprise me because AF usually progresses.  I am presently going through an increase in my AF though, but hopefully it is only temporary.

Clearly Stache you need to assess what this means for you personally in view of you heart condition.  I see you have stents for coronary heart disease.  Your doctors will obviously want any high atrial rates to be well controlled as well as controlling the duration you are actually in an atrial tachyarrhythmia.  But try not to worry.  That will only cause stress and make any palpitations worse.  Your doctors will know how best to manage this.  My last 12 month AMS count was down to around 1000 (from 2500+ previously) so I know my AF is being controlled, the little pest.

What are your symptoms Stache?  Hopefully they are minimal


by Stache - 2022-08-22 21:34:16

My symptoms really started after the doctor took me off 

A lot of the symptoms started after the doctor took me off Pradaxa blood thinner medicine that lowers the chance of blood clots, Prinivil ACE inhibitor, and Plavix.  I am still taking two other meds daily.  Seems my blood is back to normal and can clot now, but I have fatigue now that I didn’t have while taking all the meds.  I am always hungry and drink a lot of water, and my eyes get a little blurry and I see sparkles now and then.  I don’t get dizzy as I used to on the blood thinners.  I do feel hot when it is not but this is California and it has been HOT here 

I walk for one hour every morning and a couple times a week ride my bicycle after walking for 2 hours.

Strange as it sounds I can feel my heart flutter and the shocks my pacer puts out.  My blood pressure is constant as I check it morning and night and record it since my cardiac arrest 3rd degree 02/08/2021.

Automatic Mode Switching

by Marybird - 2022-08-22 22:48:20

I can't add anything to Gemita's explanation of the purposes of AMS and how it works, but maybe relating my own experiences with AMS might go a little way in addressing your questions about being concerned with AMS incidents.

I have had paroxysmal atrial tachycardias for years, and have been on beta blockers and diltiazem which generally have done a great job of controlling the tachys. I also developed sick sinus syndrome over the years. So it became tachy-brady type and ended up with a dual chamber pacemaker to keep the heart rate from falling too low, with metoprolol and diltiazem keeping the tachys at bay.

I'm under the impression that the AMS settings, including notification of a patient's doctor/pacemaker clinic personnel for AMS activity  are variable,,set at the time of implant or at the first post-op pacer check according to the instructions of the EP/pacemaker technician. The settings include the heart rate at which the clinic/doc should be alerted. 

I was notified the first time by my cardiology office that they had received alerts from my pacemaker monitor of excessive automatic mode switches ( there must be an minimum acceptable number of those, anything being above that number is excessive). These were related, in my case, to increased incidents of tachycardia, and I was instructed to increase the amount of metoprolol I was taking. 

I was notified again of monitor alerts about 6 months later- not sure if they were excess AMS, or tachycardia alerts, or activity seen in a routine remote pacemaker monitor report ( they didn't tell me), but I was again instructed to increase the metoprolol. I learned in a later office visit that the reports were showing short runs of A-Fib ( new to me) and the metoprolol was increased to stomp this down. 

The third time I was notified by the cardiology office it was to inform me of alerts they had gotten from my remote monitor of a couple of several hours' long A-Fib incidents. They instructed me to come in to see the cardiologist, who handed me a diagnosis of A-Fib and a prescription for Eliquis. I continue to take the metoprolol and diltiazem, which control the heart rate well, so even though there may be occasional incidents of A-Fib, the heart rate generally isn't too high, the incidents last less than 30 seconds, ( I think, can't always feel them), and my A-Fib stroke risk is minimized by the Eliquis.

So now, there might still be occasional episodes of excessive AMS on my remote monitor reports, or even alerts to my pacemaker clinic personnel. But now,  they won't be concerned if those reports show more or less similar information as before, because they've already taken the necessary clinical action ( ie, increased rate control medication and Eliquis) to minimize any symptoms, keep the heart rate under 100, and stroke risk mitigation). Those reports just go into my health records. If the alerts (excess AMS or others) indicated a change or problem with either the pacemaker, or the patient/heart activity, this might well be a cause for concern and indicate a need for a clinical action, so the patient would be notified by the clinic so this action could be taken.

As for your AMS alerts to the hospital, I'd figure that the alert may have been generated because whatever was reported exceeded a preset threshhold for the event. Whether or not they notified you about them ( other than just seeing them in a report) depends on whether or not they considered them actionable, ie, need to do something about what's happened. If not, they may not contact you about the report. 

So really, as far as your increase in your AMS events being a matter of concern, that is a question best addressed by your pacemaker clinic/hospital. They can tell you ( show you in an in office check) exactly what caused those AMS incidents, explain how changes in your settings might have contributed to the increase, or just what's happening. 



by Stache - 2022-08-25 21:32:48

Today I had a very lengthy conversation with my cardiologist (the squeaky wheel gets the oil), about the AMS and my atrial fibrillation.  I have been assured the pacer AMS is doing exactly what it was designed to do in my case and yes I have had some severe AFib events that lasted for many hours back in March while I was taking Pradaxa at the time.  In June my Pradaxa prescription ran out and I was taken off Pradaxa.  However, today the cardiologist put me back on Pradaxa as the AFib sessions are still happening but not as bad as in March.

I have spent the day reading AFib studies and have concluded vitamin C 500 mg twice a day is better at reducing AFib as an alternative to other drugs.  I did pick up my prescription of Pradaxa today but it does have a lot of side effects for now I am willing to go back on Pradaxa until my AFib calms down as it will never go away.

I was told I am considered a high-risk patient and have been placed on the 24/7 tracking program another reason Pradaxa was prescribed.  The good news is all of my blood tests came back with great results today.  My everyday exercise plan has paid off of walking for 1 hour every morning rain or shine mostly shine here in Northern California and riding my bicycle 2 to 3-times a week on 20 to 40-kilo rides.  At this point, there isn’t much I can do but keep up my exercise, stay on my diet, and just hope for the best.

Thank you for the updates

by Gemita - 2022-08-26 01:45:06

Stache, I am a Vitamin C believer too (taken in non acidic form as Magnesium Ascorbate or Calcium Ascorbate).  Cannot take Ascorbic Acid because of bowel distress.

Pradaxa?  Not sure of the difference in cost where you are but Eliquis anticoagulant might be a safer option.  Many take Pradaxa but Eliquis can be easier to tolerate, with fewer side effects and potential risks. 

Providing heart rate when in AF is well controlled and that we are protected from the risk of having an AF related stroke by taking an anticoagulant, my doctors are not overly concerned.  What counts too are "symptoms".  Difficult symptoms can help determine whether or not to try to better manage AF by having an ablation.  Like you I am trying to manage my condition by lifestyle changes although you sound as though you are better at exercising than I.  

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