What does a "rate responsive" PM do?

I had a "dual chamber rate responsive" PM from Medtronic installed Monday 14th December. My problem was low pulse, down to 7 seconds between heartbeats during my sleep, in combination with flutter.

The PM is programmed to keep my pulse above 60 bpm, and it seems to work just as intended. When my pulse drops slightly below 60 bpm, a correction occurs immediately, bringing the pulse back above 60 bpm. The doctor told me it gives my right atrium and my right ventrikkel a 0,5 volt stimulation.

On my first check-up, just a few days after the operation, the PM had been in operation 74% of the time, a surprisingly high percentage.

Is the rate responsive-function of the PM mean that it also is in operation above 60 bpm? And how is it working at the various pulse levels?

I use a sports watch and keep my pulse below 120 bpm, and intend to take it easy for the coming 2-3 months. But when the PM and the wiring is settled, I intend to go back to running, swimming and all kinds of sports again. So how then, will the PM respond to pulse above 120 below 160? And if my pulse exceeds 160 bpm, how will the PM respond?

2 Comments

rate response

by golden_snitch - 2010-01-10 08:01:37

Hey there!

Yes, when the rate-responsive function is activated your pacer will make sure that your heart rate reacts adaquately to your level of activity. It will kick in when your own rhythm is not responding fast enough. Now, not everyone needs this function. It will pace your heart anywhere between the minimum and maximum programmed rate. I don't know what your upper programmed rate is, but mine is 155 bpm, and when I exercise the pacer often paces me up to this rate. In case your own rhythm is able to go faster than the upper programmed rate, it will just take over. This upper setting doesn't necessarily mean that your heart rate can't go any higher. It does in my case because I have no good underlying rhythm that would be faster than the pacer.

Now, there are different sensors a pacer can use to adjust the heart rate adaquately. Medtronic pacer's have a so-called "accelerometer": "An accelerometer is basically a tiny electronic component that senses the degree of vibration in the body (when you move, it causes the tissues of the body to vibrate) and increases the heart rate in proportion to the amount of vibration (and hence the amount of movement)."
My pacer which is a Sorin Group has two sensors: accelerometer plus minute-ventilation. But for most people the accelerometer alone is sufficient.

I'm pretty sure that your relatively high pacing percentage (is this atrial or ventricular?) is due to the rate response being activated.

Best wishes
Inga

Upper programmed rate

by otbergo - 2010-01-10 12:01:52

Thank you for your well informed info. My PM is programmed to pace my hearth between 60 and 160 bpm. The first 4 days, I think it might have accelerated my pulse a bit too much, because the slightest movement gave me a pulse of 150-160. It really was terrible. As far as I could understand my doctor, the highspeed pulse of the atrium forced the ventricle into the same frequency.

After an adjustment, I'm able to keep my pulse between 60 and 120 bpm. When my pulse exceeds 120 bpm, I just take it easy, and the pulse falls quite quickly. I'm able to increase my level of activity little by little, without exceeding 120 bpm. I'll see my doctor again this week, and is very curious to know the readings from the PM. I've asked for a PM reading device, but Medtronic doesn't have developed such a patient-oriented device. I'm using a sports watch to check my pulse, but I assume a reading from the PM would tell me much more of how the hearth and the PM work together!

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