Which Mode?

How do you know which mode your pacemaker is set in? I am advised VVI would be the best for me. I had an AFib episode last week and my pulse felt as irregular as it ever did when I got an attack. I am told this cannot happen with paced ventricles on my dual pacemaker and following an AV node ablation.

However on another site it was suggested that unless I was set in VVI mode, then a signal could break through from the atria and the PM would follow it? Is this true? I felt the Pacing Clinic didn't believe me and told me not to feel my pulse! No need as I can always hear it in my ears anyway..... My husband confirmed an irregular beat at the time. Lasted about an hour. Tracings showed nothing untoward, so I am baffled. As my AFib is paroxysmal, then I am fine at the moment.

5 Comments

115...

by golden_snitch - 2015-05-17 01:05:40

... is probably your upper tracking rate. The ventricular pacemaker lead will track the atrial rhythm up until that rate, but you cannot go any faster. Some pacemakers are programmed to go into a 2:1 block when the upper tracking rate is reached, so that they drop, for instance, from 160 to 80 bpm. It's not a mode switch to VVI, though. My pacemaker does the 2:1 block at 190 bpm (atrial rate).

Mode switch feature

by golden_snitch - 2015-05-17 09:05:10

Hi JoMarie!

If your AV-node ablation was successful and there is a complete third degree block, Afib can no longer cause your ventricles to beat irregularly. The pacemaker/the ventricular lead will never track an atrial signal that's as fast as during an Afib episode (> 400 bpm in the atria). It cannot keep up with that, and it has safety features to avoid such tracking behaviour (mode switch).

Today's pacemakers all have special features to respond to atrial tachy-arrhythmias, like Afib. My pacemaker has a mode switch from DDDR to VVIR if I should ever suffer an episode of an atrial tachy faster than 200 bpm. That is a very common feature that most, if not all, pacemakers have. So, no need to program you into VVI all the time, the pacemaker can switch into that mode when you have an Afib episode. VVI can lead to pacemaker syndrome which means that the atria and ventricles do not beat insync. One usually only programs this mode in patients who are in Afib (or any other permanent atrial tachycardia) all the time and who had an AV-node ablation. In those patients there simply is no chance to keep atria and ventricles synchronized. But as long as you only have episodes of Afib, you should stay in DDD with a mode switch.

All the best!

Mode Switch

by JoMarie - 2015-05-17 11:05:52

Thank you so much gs for your informed reply which I think I understand. So if I felt an irregular beat for a period, what would that signify? Is it possible what I felt was the PM switching around trying to cope with the episode? I had palpitations which felt quite strong. I think I heard that I was turned up to 115, so that would be the rate at which the atria could beat before switch....

Mode switch

by golden_snitch - 2015-05-17 12:05:20

115, are you sure? Usually a mode switch for atrial-tachy is not activated below an atrial rate of 180 or 200. Otherwise the pacer would switch, if you just do some daily life activities or exercises, because 115 is for instance a common rate when one climbs stairs etc.

The palpitations could have been caused by the atria and ventricles not beating insync (atria fibrillating, pacemaker stimulating ventricles). I always get strong palpitations when my own atrial rhythm kicks in, and I'm suddenly not paced in the atria and ventricles, but in the ventricles only. Also, you might have felt the switch and, not sure about that, the pacemaker might have checked regularly whether you are still in Afib or not. But this only applies if you are set in DDD with a mode switch. As long as you are set in VVI, there won't be any mode switches.

Mode Switch

by JoMarie - 2015-05-17 12:05:29

Now not sure what the 115 meant, only that it was turned up to that as just after implant I had a severe AFib and they spent a long time adjusting, even calling in a doc to verify that something was breaking through and it was set too low.

All this started last week, when at a pacing check, the tech said he was turning down something as it seemed no longer necessary and would 'save the battery'. Following my first AFib and feeling ill in over a year, then I linked it up with what he might have done, but they said nothing had been changed (or recorded as changed!) When I said I had had an irregular pulse for a while, they said it was not possible as the trace showed nothing untoward other than an AFib episode (paroxsymal for an hour), and as it was not possible to feel an irregular beat, and suggested I didn't feel my pulse! So I felt like a hypochondriac who must be imagining things and was not believed. But during that night I was woken by it and my husband also felt what he said was the AFib pattern - I guess I will have to wait and see.

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