Biotronik Rate Response (Acclerometer) vs. CLS (Closed Loop Stimulation)

I asked a question in another post about bumpy roads affecting my Biotronik pm.  I was confused about the difference between the Biotronik CLS setting and the rate response setting.  Penguin provided a link that explained a lot.  Adding here in case anyone else may find it helpful.  It seems especially relevant to those like me who exercise a lot.  Looks like there are a lot of previous posts about having difficulties getting the settings right and it may be because the gain sensitivity can be automatically adjusted based on patient activity.

Here is the difference between CLS and regular rate response:

"Rate-Adaptive Pacing

The device achieves rate adaptation through programming of either standard motion-based pacing via a capacitive accelerometer or by the means of the principle of closed loop stimulation (CLS) which involves the translation of myocardial contractility into patient-specific pacing rates.

for standard motion-based rate adaptation, the pacemaker is equipped with an accelerometer located on the hybrid circuit of the pacemaker; this sensor produces an electric signal during physical activity of the patient

when in CLS mode, the pacemaker monitors and processes the intracardiac impedance signal associated with myocardial contraction dynamics; changes in the waveform of this impedance signal are associated with changes in the contraction dynamics of the patient’s heart due to the heart’s inotropic response to exercise"

Apparently, both types of rate adaptation can be set to automatically adjust sensitivity gain to the patient's activity level.

"When the Automatic Sensor Gain setting is programmed, the Sensor Gain parameter is adjusted automatically.

the device samples the sensor-indicated rate

the sensor gain is increased by 10%, if the activity rate does not reach or exceed the programmed activity rate (fixed to 90% of maximum sensor rate) for 30 minutes each day over 7 consecutive days; an increase in gain cannot occur more often than every 7 days

if, during the 24 hour period beginning at midnight, the activity rate reaches or exceeds the programmed activity rate (90% of maximum sensor rate) for one hour, the sensor gain setting is reduced by 10%

a change in the sensor gain only occurs at midnight

The Automatic Sensor Gain function is primarily influenced by the Maximum Sensor Rate setting. Therefore the Maximum Sensor Rate must be appropriately selected."

"The device can be programmed to use a unique rate-adaptive principle called Closed Loop Stimulation (CLS) to adapt the patient’s pacing rate. The DDD-CLS and VVI-CLS mode use the CLS concept to determine the pacing rate variations.

the device measures electrical impedance by injecting a small AC current between the pacemaker case and the ventricular electrode tip

the induced voltage (which is proportional to the intracardiac impedance) is measured between pacemaker case and ventricular electrode tip

When the pacemaker is programmed to CLS rate adaptation, the pacing rate during CLS-driven operation will never exceed the programmed maximum closed loop rate."


Handy Website!

by Penguin - 2023-02-02 14:27:22

That website is really useful - if a little technical! 

Thank you for the link and explanation. I see now what is meant by 'the device needs to learn about you' e.g. learning your activity levels and responding over a 7 day cycle. 

It may help you also to request a copy of the device manual, (the technical one). Again - complicated - but it gives you all of the possible settings for the device. Running through these with a Biotronik Rep and exploring the limitations / possibilities of the useful ones would possibly help most.  The Rep can usually add the detail such as how different settings are inter-dependant on each other and the limitations of each.  The manuals don't always explain those things! 

You can contact a Biotronik Rep via their website. Give it a try.  

You've learned loads in a brief amount of time. I hope it's helped you get a better understanding of it.  Getting to know it's foibles may help you feel better about it and more in control - or at least help you understand when something bizarre happens. Knowing the beast is half the battle and empowers you to challenge the programming and ask for what you need.

I suspect you will become our Biotronik 'Go to Expert' in time. Well done you! 

Best Wishes


Product manual

by Daedalus - 2023-02-02 15:47:40

Click here for the manual download.

Light bedtime reading

by Mad Hatter - 2023-02-02 16:19:24

Thanks for the idea Penguin and for the link Daedalus--you've just given me something to keep me busy for the next few days!  


by Penguin - 2023-02-02 19:30:04

That manual is a very complex document and goes into a great deal of detail compared to others I've seen. You'll need support to understand it as someone new to pacing.  

It's kind of Daedalus to provide the link.  Have you found it patient friendly Daedalus? 


Biotronik Manual

by Gemita - 2023-02-03 03:30:47

Mad Hatter, thank you for making a separate post studying the difference between the Biotronik closed loop stimulation and the Biotronic Rate Response (Accelerometer) settings.  Not an easy read!

Just had a peep at the Biotronik manual (thank you Daedalus) and although I would have to re-read a lot of it or research certain features further to better understand them, it is an excellent manual, really well laid out.  I have just compared it with my Medtronic manual and actually both are very good.  We just need time to absorb them and to familiarise ourselves with their content.

Just discovered an answer in my Medtronic manual to a question that a member asked about having a pH impedance test to evaluate acid and non acid reflux from the stomach into the oesophagus.  Now who would have thought I would find reference to this in my manual?  It clearly states:  Capsule endoscopy and pH procedures should pose no risk of electromagnetic interference. This is just one example where our pacemaker manuals are really the first place to go and together with a telephone call to our device manufacturer representative or to our own pacing clinic technician, we should be able to get all the support we need to understand what is going on in our little devices.

Penguin, I certainly find the Biotronik manual patient friendly, well laid out and full of interesting information.  My Medtronic manual mainly focuses on the “how to operate the device” which is something none of us would be allowed to take on anyway, whereas the Biotronik manual focuses more on what each Settings feature has to offer, so in that regard it is far better than my present Medtronic manual which I think needs an upgrade now!


by Penguin - 2023-02-03 09:40:41

 My point is that it's very detailed and 142 pages is a lot to get through if you're new to pacing and you're not sure what you're looking for! You're a very experienced patient Gemita and your answers on the forum evidence that you spend a lot of time going to the trouble of researching and understanding a wealth of different issues that members bring to the table.  

I'm trying to see it from the perspective of someone new to pacing. I'd have been completely fuddled years ago and have to admit that 40 pages in I was losing the will to live!

The Medtronic manual is pretty basic in comparison. That's what I'm used to!  


You know you're wired when...

Muggers want your ICD, not your wallet.

Member Quotes

Good luck with your surgery. It will improve life amazingly.