Voltage setting ?

I've had my PM since Oct. 2012. St. Judes, SR RF 1210.
I've recently transferred my care to my local area, it was with a group 40 miles away where I was previously employed. Had my device checked and the tech reset the voltage from the previously set 1.5 volts to a new setting of 2.5 volts.
The new setting made sleeping on my left side untenable. I couldn't handle the very noticeable annoying thumping in my chest. I shift from my right to left during the night as a matter of personal comfort. You might say that's the way I roll.
I'm not overweight nor do I have high clorestoral (sorry about spelling), I'm not diabetic. I was given an atrial oblation at the time of my implant. So, I'm apparently totally dependent on the PM.
The new tech told me the the higher setting was the norm at my new cardio clinic. I returned one week later and insisted it be reset to 1.5 volts. The tech attempted to dissuade me but I persisted and insisted. I saw no reason to fix what wasn't broken and it certainly was affecting my sleep. The tech was a bit p.o'ed as I referred to the new setting as generic. To me setting the PM at the higher voltage would entail battery replacement 40% sooner than the originally projected 10 year battery life. That would be in 6 years.
I guess after all the above yammering I'd like to get an idea of what a typical voltage setting is.
I'm not over weight, there is no defib in this unit, not necessary, no previous history of heart disease, though afib was diagnosed about 3 years prior to the PM, it would come and go, I was asymptomatic. I'm 63 years old.
I've always been provide with a print out of my PM settings but am not sure what I'm looking at. Is there a good source of info to interpret what I'm looking at?

2 Comments

Outputs

by AndyJames - 2014-05-29 06:05:10

Hi. Because of your AV node ablation you're most likely dependent on your pacemaker to keep your heart going. As a pacemaker RN I rarely set my dependent patients with a fixed output below 2 volts because if something changes and the lead fails to capture they will be in serious trouble. I've found that the longevity of the device isn't usually reduced by more than a year and I think it's worth it to provide the extra safety cushion. Compare the 'Longevity' seen at the top of the 'FastPath summary' on your printouts and you'll see that the longevity probably didn't change much with the pacemaker at 2.5 volts compared to 1.5 volts.

Your model (Accent SR 1210) pacemaker has an auto-capture mode that I'm a fan of. It automatically tests the thresholds and adjusts the outputs to provide a slimmer margin and less waste of battery but it can increase the outputs up to 5 volts if the amount of energy needed to capture increases. This allows the pacemaker patient the best of both worlds as far as safety and improving battery longevity, but it doesn't work for everybody so they may have tested it and found it wasn't appropriate for you, but you could ask about it at your next visit.

Unless you're talking about extra-muscular stimulation which is very rare with your type of pacemaker the pounding feeling in your chest shouldn't change regardless of how much energy is being delivered. The electricity travels through the heart cells like a row of dominoes falling over. All the pacemaker does is knock over the first domino so it doesn't matter if the pulse is 5V or 1V (if it captures) the heart beats the same way. The increased pounding sensation in your chest may be coincidental or even a nocebo effect of the setting changes of your pacemaker.

Voltage and threshold

by golden_snitch - 2014-05-29 11:05:55

Hi Paul!

There only general rule I know about voltage settings is: threshold x 2-3. The threshold is defined as the minimal electrical stimulus required to make the ventricles/atria contract. If the threshold is, for instance, 0.75, then the voltage should be at least 1.5V. That is the typical voltage setting, and since patients have different thresholds, it varies. The norm the tech was referring to could be the 2 x, 2.5 x or 3x the threshold.

Programming the voltage that way is a kind of safety measure to make sure that the pacer stimulates effectively, even if the threshold should rise a little. Thresholds can change, even on a daily basis, that's why most pacers today automatically check the threshold, for example, every 24 hours, and adjust the voltage accordingly.

In my opinion, you were absolutely right to request that the voltage be changed back to your original setting. As long as you keep the above mentioned a safety margin, you should be fine.

Just one question out of interest: It sounds like you had an AV-node ablation. But then you say you had Afib that came and went, and that you were asymptomatic. Now, an AV-node ablation is usually the last resort therapy for VERY symptomatic Afib patients who have exhausted all other treatment options. So, I'm a bit surprised that you apparently had this done, without being symptomatic.

Best wishes

Inga

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