It will depend on what brand pacemaker you get. They all have different features to combat these issues. It will also depend on whether or not you get just a pacemaker, an ICD, or a BIV-ICD. All have pacing capabilities.
That having been said, if you get a strictly low power device (only a pacemaker) then the risk of damaging the device is essentially zero, however you may cause it to pace when it doesn't necessarily need to, the only side effect you would notice would be the occasional palpitation, caused from an extra beat from the pacemaker every now and then.
The issue has nothing to do with the actual wavelength of the noise, but rather the way the pacemaker (or ICD) itself works. They are designed to sense very small electrical currents (the ones in your heart) and use a wire placed in one or more of the chambers in your heart to accomplish this. However, you can overwhelm the device and basically blind it, by introducing noise at such a high amplitude that it prevents the pacemaker from seeing (sensing) the signals it needs to (the ones from your heart). When this happens, the pacemaker resorts to a noise reversion algorithm, and will pace at a set rate, until the noise subsides and it can tell what is going on again. Better to err on the side of caution, and pace when it's maybe not needed, than not to pace when you really do need it. If it did the latter, you could / would pass out, perhaps suffer injury, or even death.
As far as damaging the device, they are all built with zener diodes in the output circuits, to prevent current from flowing backwards into the device and damaging the circuitry (such as what might happen if you are defibrillated externally or perhaps shock yourself changing a plug, welding etc). The risk of you damaging the device is small, however, if you did manage to take enough current to damage the device, probably you are going to die from the shock anyways so it would be a moot point.
If you do take a shock (such as welding DCEP or using AC TIG with aluminum, no gloves and leaning on the work etc) there is a small (and I mean very small) chance that you could corrupt the memory in the device. They all have dual sets of memory, which is error correcting, but if it is corrupted past a certain point it can't correct itself anymore, and will basically reset itself. This is called POR or power on reset. Basically it goes off for a few seconds (2-5) the comes back on with out of the box factory settings, it will still work, but won't be customized for you. You can return to the doctor to have it checked / reprogrammed no problem, and carry on as normal.
If you get a high power device (ICD or BIV-ICD) then you run the risk of getting an unnecessary therapy (cardioversion / defibrillation) which will hurt like hell, make you sore, scare the crap out of you, but won't really HARM you unless you do it over and over and over again. Some manufacturers have better discriminators than others to prevent unnecessary therapies, some work great (Medtronic) some dont (St Jude, Biotronik, ELA, Boston Scientific, listed in no particular order). These are the same discriminators that attempt to tell the difference between A-fib with rapid ventricular response, and V-tach, and SVT, AVNRT, V-Fib, etc. Some need a therapy, some don't. Some need one, but not the same as the others.
I am not sure where you are, if there is socialized medicine, if you have a choice etc. I would, if it were me, request a Medtronic device. They have the best battery life, best discriminators, best remote monitoring, and in my opinion are miles ahead of their competition in all aspects of the business as far as CRDM and pacing are concerned.
Now, all that being said, because of the litigious society we live in, they are going to give you a huge book of what not to do, and welding is in there, with about 9000 other things.
Long story short, wear gloves, don't lean on the work, and don't work between the cathode and anode (the work lead and the ground), keep the anode (the work ground) as far from you as you can, and stay away from large magnets. Oh, and don't get inside the microwave and turn it on. If you follow those precautions you will be fine.
Oh, and I would find an eletrophysiologist to insert my device if I had a choice, but that's just me. I would rather have the guy that does 100 a month do mine, than the guy that does 10 a year.
Your mileage may vary, no warrant neither expressed nor implied, rinse and repeat as necessary, side effects may include itching, irritation, baldness, erectile dysfunction, anal leakage, and flu like symptoms. Yes, it is possible that I stayed at a holiday inn express last night.......
If you read this far, and still have questions, you can PM me and I will be happy to discuss it with you on the phone.
Be Safe
Shane
and run their cnc plasma table 
) have the pleasure of having one of these put in.
) that I might (or might not) have to factor in
it goes that far, I will, without saying raise what I do for my living and ask what can be done to avoid any issues 
but thought it would be good to ask the question on this site 
