Means of Telemetry

I just had a Medtronic dual-lead/dual chamber pacemaker installed. I am 4 days post-procedure. 12 hours after the operation, a representative from Medtronic came in at 0-dark-30 and woke me from a fentanyl stupor, and strapped me in, after placing what appeared to be a blue hockey-puck with leads over me left shoulder. When asked what the hockey puck was for, she replied that it allowed her to "log in" to my device and download statistics on heart rate, frequency of pacing, and percentage of battery used. She would not give me any really useful information, such as "what RF frequency does the device communicate on?" and "is the data encrypted", and "is there a password to my heart".

Being an engineer, I am less interested in the fact that this device paces my heart and much more interested in the datacom aspect of the device. It is clearly wireless, and I am thinking about hooking up a scope and an antenna and looking for the signal.

Does anyone know how this little chunk of metal communicates through my chest wall to the blue hockey puck? I am really curious. I al also REALLY sore - when does THAT little inconvenient side effect go away?

Thanks!

Tom Davidson


7 Comments

Communication with programmer

by peter - 2007-11-15 01:11:40

Good question. I am certain that it is radio frequency communication. It will be encrypted using the makers programming so I dont think you will be able to see anything except gobbledygook even if you could sense the digital signal. You could always buy a programmer if you win the lottery. They cost about £15000 or $30000
Best not to even try.I doubt if even the pacing technicians know the frequency as its no use to them and they dont need to know. Its almost certainly between 4 and 200 megacycles I suspect. Peter

Welcome, Tom

by NH - 2007-11-15 03:11:41

I too am new to the Pacemaker club, but not new to the Pacemaker. I had my first one for 5 1/2 years and have now had my Pacemaker changed out for a new one which may last 9-12 years.

I have learned to pay close attention to the instructions you are given by your Dr.

No lifting at all for a few weeks
DO NOT RAISE YOUR ARM OVER YOUR HEAD on the side where your Pacemaker is located until the Dr. says you may.
Mostly you will not be able to sleep on your Pacemaker side for a while.
DO NOT try to connect with your Pacemaker with another wireless device. It would be risking your health to do so as you might upset the pulsing of the Pacemaker. This may not be a very scientific reason, but please listen and don't do this.
Also, don't get the area wet until the Dr. says you may. No showers until the Dr. tells you it is OK.
You will no longer be able to go thru the screening "door" at the airport, you must be patted down and I just tell them that before hand. The airport screening "door" is set much higher (I have been told) than the screening at stores, etc. In stores and supermarkets, just go thru them quickly and don't stand close as they might interfere with your Pacemaker.

I have a St. Jude Medical Pacemaker and the St. Jude tech. is always very nice. I am always told what he is doing. First, he puts the magnet over my Pacemaker and does what is called a Pacemaker interrogation. At this time the Pacemaker gives out the info. it has stored in it's memory. It will tell the tech. if I have had any unusual events, such as a really fast heartbeat and on what date this happened.

Then he takes the Pacemaker down to see if my heart will pick up by itself and at what pulse. Then he puts the Pacemaker back to normal pulse. I often times have a headache after the procedure.

I am by no means a medical person, or scientific person or computer guru. I just keep try to learn all I can and to know my own body as well as possible.

This is some things I have learned and that have been beneficial to me. Hope they help and again WELCOME!

Take care,
NH

Don't know much, but...

by sboissonnas - 2007-11-15 05:11:18

Hey Tom,

I'm an engineer by training, if not by trade, and I want to know too. I don't know a whole lot more than you do, but I do know that it's a magnet they put over your heart, and it has to be circular. (Your hockey puck. In my case, it's a thin hollow circular wand.) When a circular magnet (presumably of a specific magnetic strength?) is placed directly over your pacemaker, it puts your pacemaker into a special mode (unfortunately I can't remember the term they used at the time - suspend, maybe?) from which they can interrogate and control it electronically.

How they interrogate it and send/receive data from it, I'm not entirely sure, but I always thought it had to do with varying the electromagnetic field created by the circular magnet.

If you find out the real story, please let us know!

-Stephanie

PS: When I read your comment about being sore, I thought you meant that the pacemaker interrogation made you sore. I see now I probably misunderstood, but I too get a little bit sore and feel very strange after the PM interrogations. It's usually gone somewhere between half an hour and two hours later, depending on the tech who checks me. (Some are more vigorous with the tests than others!)

Frequency...

by dward - 2007-11-15 08:11:34

First, hockey pucks are black, not blue. Take it from me - I am Canadian... there are no blue hockey pucks!
Second, that little PM can hold 10 pages worth of info!!! I think mine even has a GPS!
Third, the transmission capability of these things is obviously very weak. Being an engineer, you likely understand the rationalle behind that.
Fourth, the frequency in which they operate is

tom

by jessie - 2007-11-15 12:11:28

it takes about six weeks or it did me for the soreness to subside. everyone is different tho. the soreness sometimes returns if i carry heavy things. it will get better tho. as far as the engineering part you have to wait for someone else like smitty to answer you. welcome to the club jessie

GPS?

by tomdavidsonjr - 2007-11-18 12:11:56

GPS? Cool!

One week follow up yesterday. I have been having some difficulty breathing, so they did another chest x-ray and echo. I have a teensy little pericardial effusion, which is what he thinks is causing the heavyness.

Anyways, he decided to interrogate my PM, just to make sure everything was copasetic. This time, instead of being stoned on fentanyl, I was sitting up and lucid, and the good doctor was kind enough to show me the ropes of the interrogator. Not much to it. It even looks to be written in Visual Basic. He let me watch everything he did, though he didn't actually know how the engineering aspects worked, so he wasn't much help there. It appears that there is no password nor logging in. This bothers me a bit, but I think "dward" (above) has a good, if incomplete thought - the signal is probably very weak.

As an engineer, I would like to believe that there is some sort of pairing that is done between the device and the puck, but I am starting to doubt it. It would not be feasible, I guess, since these readers appear to be in most EP offices. So hopefully no one decides to use the Medtronic equivalent of "Air Snort" to hack my heart :)

My wife wants to know when she gets the remote.

Tom

Monitoring the pacemaker

by ElectricFrank - 2007-11-24 11:11:51

Tom,
I haven't figured out how to interface with it as yet. My concern with playing around with the interface is that it is two way and conceivably I could change some critical settings. What I have done is hang together a ECG monitor that records the waveform of my heart. I have found that by putting one electrode just below the pacer and the other just at the lower edge of the rib cage I can see both the heart chambers and the pacer pulses. The system is just an instrument amp (Analog Devices AD620) and an A/D converter. The original interfaced to the parallel port on a PC, but now I have got fancy and go into the USB port.
This has been very helpful in getting the pacer programmed optimally for me. The first thing I ran into was the rate response. Any time I did anything that caused shaking of the pacemaker would make my heart race. I watched the pacer output while I twiddled the pacer and could see the rate ramp up. I also found that I didn't need atrial pacing anyway so I asked to have it changed to DDD mode which is atrial sense and ventricle pace.
By the way I designed and manufactured biofeedback equipment for a number of years.

frank

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