Metal workers and ECGs

I learned that when a person works with metal, his ECG will have lots of interference and be essentially unreadable. I had an experience with that yesterday and I was sure the machine was malfunctioning until I called in a co-worker for help. One look at the printout, and she asked the guy if he was a metal worker. He was.

What would happen if he would someday have a heart attack and need an ECG to see what’s going on with his heart? What are the alternative tests that can be performed on him to assess his cardiac function?

Also, where exactly is the metal located in his body? Embedded in the skin? In his lung tissues? If he would quit his job, would the problem gradually fade away, or is the metal in there forever?

…I have been a critical care nurse for 22 years and have done thousands of EKGs. I have never been taught this or never heard of such a thing. IMO, poor EKG=poor technique or uncooperative/difficult patient.

This doesn’t make sense from an electrical standpoint, either. Unless the patient came in for his EKG literally coated with metal dust, his electrical characteristics aren’t going to vary considerably (if even measurably) from the norm. Metal dust particles themselves are too small to be effective antennas for any sort of EM radiation that might conceivably affect an EKG. At worst, I can imagine such dust particles embedded in skin pores, but I can’t see this having much effect. An MRI, perhaps, but not an EKG. Sounds like a medical UL to me.

Well then I don’t understand why I was having such a hard time with this guy.

I admit that I’m not an expert on this subject and I’ve only been doing this for 3 months, but I don’t usually have trouble getting a nice clear reading. With this guy, I spent 20 minutes trying to make it work. I readjusted the bulbs (we use an old suction-bulb ECG machine) several times, made sure he was very relaxed, checked that he’d removed all metal from his pockets and turned off his cell phone and put it across the room. The interference was in all leads, no matter what I did. I reset my machine, checked that all the wires were hooked up properly and not crossed, and tried some more. I then unhooked him, brought him to another room, and used a second machine, but still had the exact same problem.

When I printed it out to show my co-workers and the doctor, they all said immediately upon seeing the pattern: “oh, he works with metal!”. So I don’t know how true it is, but they all seemed to agree on it, and he did work with metal. They’d had experience with this sort of thing before.

Instead of being straightish lines interrupted by blips, like it usually should be, it looked like someone had superimposed a seismograph printout on top of it.

If we’re all wrong and it isn’t caused by his exposure to metal through his work, then what else could have been causing a problem like this?

Fine muscle tremors in the patient or what’s known as 60-cycle interference come to mind. (IMO, if they didn’t teach you about 60-cycle interference in EKG class you were not taught properly.) The equipment might be causing the problem, too. I haven’t used suction cup leads for at least 10 years. They have to be cleaned regularly and kept meticulously clean to get an acceptable EKG.

To answer another question in the OP, about what else could be done to find out if the person had a heart attack, the standard test today is to obtain serial cardiac isoenzymes, specifically CK-MB and Troponin levels. Troponin levels rise and fall predictably after a myocardial infarction, and can be used to gauge the severity of the event and the time since the infarction happened.

I just want to clarify - I’m not a nurse and I’m not working in a hospital, where the ECGs are being used in diagnosis of cardiac patients. I work at a screening center for a place that runs clinical trials. We’re not extensively trained; we’re taught how to attach everything and run the machine (an old machine, as you’ve mentioned), and how to recognize whether there’s interference. Make a nice clear printout, give it to the doc, who checks the patient’s overall cardiac health and then either OKs or rejects him for the study in question. I think that it’s unfortunate that we don’t get more training, because I’d like to learn more about it. I’m starting to look into it on my own, because I’m curious.

But if the problem was in the leads, as you suggest, Eggerhaus, then why would the machine have been working fine until that patient, and then fine again after him, just not for him?

I looked up 60-cycle interference, and it did look something like that. But again, shouldn’t that have shown up in several patients, if that was the problem?

It also could have been muscle tremors, I suppose, even though he looked relaxed.