How does Pacemaker Rate Response Work and How Can it be Adjusted?

Pacemaker Rate Response – Accelerometer 

I have had a question into how Rate Response works, which bits are programmable and how that affects the patient.

Now I am going to use the names of some adjustable settings that Medtronic use. Now there are similarly programmable settings on most rate response algorithms but obviously this is manufacturer specific. 
Firstly as a side note we use a code in pacemaker language that tells us how many leads the pacemaker has or more accurately how it is set up to work. You may have seen them or heard the terms, we describe pacemakers as DDD or VVI and there are many more. If a device has rate response on we put an R after this code. So a a pacemaker programmed DDD, doesn’t have rate response on. A pacemaker programmed DDDR does have rate response switched on.
What is Rate response? 
Rate response is a pacemaker function that is designed to increase the patients heart rate when they exercise.
Take a patient who had a heart rate of 60 but because of disease when they ran up a hill the heart rate didnt increase in the same fashion a healthy heart would. Enter a pacemaker, the pacemaker can use vibration (through a piezo-electric crystal) or impedance (a measurement of electrical ‘resistance’) at the end of the lead to assume that person is exercising….

This will then gently increase the persons heart rate when they start to exert themselves.

How is this adjustable for different patients?
With many algorithms in the pacemaker world there are lots of settings so it can be tailored for the patient. Here are a few that Medtronic use.
Upper Sensor Rate: Example Setting – 130bpm
When a person is exerting themselves the pacemaker will increase the heart rate up to a maximum of this rate. It will plateau at this number so long as the vigorous exercise continues. The more movement in the pacemaker the more strenuous it will predict your exercise to be and it will adjust your heart rate accordingly up to 130bpm (in this example).
When technicians program this figure we take into account many factors. For Example, the age, health and activity level are all important. Fitter, younger patients will generally require a higher upper sensor rate as their body will likely have periods of very high demand of blood and oxygen but most importantly it is less likely that their heart will have any physiological issues through being paced at higher rates e.g. 180bpm. If a patient has a cardiac history which includes Angina, we will tend to err on the side of caution as pacing the heart at a quicker rate could induce symptoms or put their health at risk.
The ‘speed’ the pacemaker increase its rate by is determined by the Exertion Response this is programmable between 1-5. A 1 would mean that the pacemaker would take its time in increasing your heart rate to the rate it feels your exertion requires. A 5 would mean the pacemaker upped your heart rate very quickly. The normal setting is quite predictably a 3. If a patient felt that it takes a while to get going when they start exercising, we would potentially look at increasing the exertion response.
A similar feature is the ADL Response, this is programmable in the same way with the same figures, but it is in reference to the ADL described below.
ADL (Activities of Daily Living): Example Setting 95 bpm
This is a helpful tool for a pottering around heart rate! Now when you potter around at home your heart rate will increase… but not by very much. Movement is minimal (therefore the vibration on the sensor in the pacemaker will be minimal). The pacemaker will ‘know’ that your exertions are not too strenuous but you are up and about all the same. So the pacemaker will bring the heart rate up to this ‘pottering about’ figure and keep you there so long as mild activity continues.
The level of movement (leading to vibration in the crystal) required to trigger the pacemaker to reach ADL is minimal.
Which brings me on to the final setting I am going to discuss with you right now, The Activity Threshold. In my head I see this as how sensitive your pacemaker is to exercise. Programmable from Low to High with a couple of permutations in between this is how vigorous your activity would have to be before your rate response kicks in. If set to Low then your pacemaker will only have to detect slight movement before rate response kicks in. This level of required exertion increases with each setting all the way up to High, where only vigorous hard exercise would trigger a rate response from the device.
It is important to add that these algorithms do have value in helping patients meet the demands of their lifestyles. However they do not always have the answers if symptoms are due to a health issue that is not treatable with a Pacemaker with Rate Response.

A complete explanation of these topics and more is available in the book Pacemakers Made Easy by Carl Robinson.

Comments 6

  1. Hi Carl,
    Your book ” Pace Makers made easy ” has been a great help to me penetrating the protective secrecy which seems to pervade the Cardiac pace making technical departments.
    My Pacemaker was implanted at the Queen Elizabeth Hospital Birmingham on 18/02/2014 ,after my Trycuspid and Pumonary valves were replaced causing Total Block ,I don’t know what grade ! I have not had a heart attack.
    The pulse rate is set between 60/120. ModeDDDRO .
    The M fg is St Jude Medical Type Zephyr 5826 Serial 4349507.
    When I had the pacemaker checked I asked questions and was initially met with what do you want to know that for ? Later I posed some Pacemaker questions to my Heart Consultant his response was ” Well really it’s your Pacemaking dept you should should speak to . I explained my problems with that department. His next response was ” Well to answer your question properly you should spend 1/2 year in Med School however I will explain simply only once” . later in a letter he said he contacted the Pacemaking Dept but could not get much information from them
    I have since transferred to the University Hospital Royal Stoke who have been very helpful and have answered some questions.
    I am still trying to find out what type of accelerometer My Pacemaker uses. I am an exRunner/ Windsurfer/Paraglider Pilot all of which I now can’t do due to knee and shoulder “Ops” . I am still very active Orienteering but walking, Trying to ride my bike and attending the “Gym”.
    My recent Histogram showed a max pulse of 115 yet when I take my own pulse when I have exercised to the point of feeling sick ,like really out of breath,my pulse taken from my wrist shows 140 . ?
    When exercising to a lesser degree my pulse at my wrist shows 120.
    When I questioned the Pacemaker tech about this ,he waffled on about double pulse which did not make sense.
    I have been checking my pulse for training purposes for over 40 years so I am not making miss reading
    Have you any idea as to the difference?
    I thought that the excess over the 120 was my own intrinsic pulse? But the histogram says otherwise.
    I look forward to learning more since I don’t think at the age of 78 any Med School will accept me LOL.
    Cheers Tony

  2. I have a rate responsive pacemaker fitted because of SA block (with slow junctional escape) and I have found that when climbing 2 or 3 flights of stairs or climbing a steep slope the movement of my legs have a natural tendency to go slower which results in my heart rate slowing down and I find it very difficult to maintain a satisfactory walking pace without getting immensely tired. Can the pacemaker be adjusted for this?

  3. Im a fire fighter and recently got a PM. I’ve been on light duty for a couple of months and hope to be released back to full duty in 2 months. My concern is the 60-130 setting on my PM. My heart rate will certainly exceed 130 bpm while fighting fire. Is there an issue with me having the upper margin set to 180?

  4. My wife recently had a PM installed. One of the problems she has encountered is riding in our truck while pulling the 5th wheel trailer. When riding on a road with regular bumps the PM will increase her heart rate to max levels. This creates discomfort and many times we must pull off the road. Any cures for this?

  5. About 9 years ago I had an attack of Atrial Fibrillation I was prescribed Atenolol but this slowed my heat rate excessively, as a result a dual chamber pacemaker was implanted. Prior to all this my normal resting pulse was 48-50, the the PM was set to 65 bpm and rate response was set.
    This meant that at 65 bpm my heart was relying 100% on the PM, that was a concern to me. I initially thought that the PM would simply prevent my heart rate from dropping below my normal average, It took about 6 years to convince the cardio and tech that it needed tweaking.
    A slow walk would raise the rate to 120+ the simple act of pulling up the blanket to my shoulder would result in a pulse of over 100 which I found distressing, I purchased a Garmin Heart rate monitor which proved my point; as a result the PM was adjusted to a HR of 55 and the rate response was disabled. With the rate response disabled that means that my heart is functioning on its own most of the time now, which gives me peace of mind.

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