Micra rate response

Minute ventilation

by piglet22 - 2024-10-22 12:45:10

Tracey

You might already have seen this

https://pubmed.ncbi.nlm.nih.gov/2463560/

It looks as though it needs two points at a distance across the chest wall.

With a traditional device, they measure the impedance between the case of the generator and the tip of a lead. This will be made up of the lead value and the tissue value.

As the chest expands and the distance changes, the impedance changes as well.

The change in impedance presumably is used to calibrate the volume change.

I can't see how you could do that with a leadless device.

thanks

by Tracey_E - 2024-10-22 12:56:19

That makes sense. With ventricular pacing, it'll only track the atria up to 105 after which it depends on rate response to get the rate up. I've been told there will be an adjustment period but being congenital heart block, my heart should adapt easily and it will not affect my ability to be active. I'm still not 100% sold, but I trust both eps and the alternative is another set of traditional leads. I have until December to think about it and decide what I want. 

Finding something better than accelerometer...

by crustyg - 2024-10-22 13:20:06

... is really quite difficult.  I *think* Biotronik have added strength of heart muscle contraction as an indication that cardiac output needs to increase, but anyone who's ever watched a scary movie will know that we get occasional 'thump' heart contractions due to sympathetic activation which wouldn't necessarily justify much of an increase in HR.

Chest impedance is surprisingly difficult: it changes with blood flow, every heart beat *and* chest expansion/contraction of breathing.  BostonSci's approach is to use a digital filter to separate out the low-frequency chest impedance changes (==breathing) from the high-frequency (==heart beats), *and* as breathing frequency can overlap with low heart rates, the digital filter has to have the centre-point adjusted as HR changes.  Seriously complicated, very steep roll-off (24db/octave, IIRC).  And of course normal breathing changes as you change altitude, so without some compensation everyone in the Rockies/in a commercial flight would have a raised HR.

Given the quality and reliability of indwelling-glucose monitors we might see an embedded CO2 sensor in the next decade or so.  However, Technical Diving chums of mine are sceptical, as oxygen-sensors in closed-loop Helium/O2 rebreathers have a poor safety record (when counting the drowned bodies), despite using multiple sensors and voting algorithms, so perhaps this tech isn't quite ready for us.  And yes, I know they are different sensors, but I think you get the point.  And we would expect something that could survive for 8+years and still give good results.

crusty

by Tracey_E - 2024-10-22 13:45:33

If I go with tradtional dual lead, I don't really need anything sophisticated for rate response. I've been doing just fine with St Jude/Abbott. If I go with Micra, it'll essentially be single chamber pacing over 105 as it only tracks the atria up to 105. They can do two Micras to have dual chamber pacing, but neither of my doctors likes that option and they both say single will be sufficient.

I'm a bit overwhelmed and confused, it feels like a step backwards. They are both well aware of my history, my activity level, and my desire to remain active.  One is adult congenital and has a lot of adult CCHB patients, the other does more complicated extractions and has experience with acive adults. Micra is primarily what he uses when he extracts someone like me who has been long term paced. 

What would be great would be if my battery had a few more years in it so they could keep working on dual chamber leadless! Alas, I've got less than 4 months left and I've met my annual out of pocket so I want to do it before the end of the year. So my choices are less than ideal leadless, or new leads. 

A dilemma

by Gemita - 2024-10-22 14:03:07

Tracey, could you please explain why your EP is now saying the Micra is a better choice than the Aveir?  What in particular concerns them about the Aveir and how is this improved by implanting a Micra?

I would have to be really confident that the Micra, would this be the Micra AV MC1AV1, is the best choice for me?  

What if you decided to go with new leads.  Would both your EPs support this and are they confident they could safely, successfully carry out the procedure?  If the answer is yes, I know what I would choose

Gemita

by Tracey_E - 2024-10-22 16:37:55

Aveir doesn't have remote monitoring and the battery doesn't last as long. The main reason I didn't want Micra originally is because they leave it in. Aveir is retrieved on replacement. However, they are working on retrieval for Micra. 

Both are fine with it if I choose to go with new leads rather than leadless, it's entirely my choice. If they can get the current leads out, then new leads would go on the left. If they can't, then new leads would have to go on the right, which is my last resort. I've always felt like the right side is my long term emergency back up plan and want to avoid using it as  long as possible.

I'm 58 now, so if new leads lasted 15-20 years, that puts me in my early 70's having another extraction.

I have reduced circulation on my left side now and a vascular surgeon will be stenting as needed after the leads come out. I really prefer not to have more put in once it's all cleaned out and stented.