Thursday, February 28, 2008

Can Hybrid Cars Interfere with Your Pacemaker?

Dr. Wes on Pacemakers, Defibrillators and Hybrid Cars:

With the interest and popularity of going "green" with hybrid cars (even with a select few of my fellow physician-bloggers) I thought it would be worthwhile to share a few tidbits about the potential for electromagenetic interference between hybrids and pacemakers or defibrillators. (Heck, maybe they'll need this info when they get older and have their pacer installed...)

If you have a pacemaker or defibrillator like I do, this information is good to know.


Blogger DADvocate said...

Does this mean you can't ride with your hubby in his Highlander?

9:44 AM, February 28, 2008  
Blogger Helen said...


From what I understand, the problem is mainly the keyless entry systems that the new cars are equipped with, which Glenn's Highlander doesn't have. Here is a good article on the topic of the Toyota Hybrids and pacemakers:

9:55 AM, February 28, 2008  
Blogger DADvocate said...

The keyless entry systems! Wow! Hidden dangers everywhere.

At least you and Glenn can ride in which ever car you wish.

10:54 AM, February 28, 2008  
Blogger David Foster said...

Gasoline engines also use electricity: for each power stroke, a high-voltage pulse is delivered to the appropriate spark plug. These systems are shielded to prevent radio interference, but the quality of the shielding seems to vary, as measured by noise on AM radios.

So, if we're going to worry about pacemaker interference from hybrids, it might also be worthwhile checking out the risks from conventional engines.

11:23 AM, February 28, 2008  
Blogger Larry J said...

So, if we're going to worry about pacemaker interference from hybrids, it might also be worthwhile checking out the risks from conventional engines.

Since conventional gasoline engines predate pacemakers by several decades, it seems reasonable that if there was an RF (radio-frequency) interference problem, it would've been evident by now.

The ignition interference you get can come from RF but it can also be due to power fluctuations going into the radio. This is an issue with light airplanes and is addressed by shielding the ignition lines, the spark plugs, and by adding filters on the power lines.

12:53 PM, February 28, 2008  
Anonymous Anonymous said...

There has to be an adequate Faraday cage - either around the electrical device causing the problem or the pacemaker (or person) in question.

Why aren't pacemakers shielded more effectively?

1:05 PM, February 28, 2008  
Blogger Larry J said...

It isn't just a matter of shielding the pacemaker. Instead, most of the problem comes from the pacemaker leads acting like an antenna and carrying the signal directly to the heart. Shielding the pacemaker leads is possible but it could make them less flexible. They need a lot of flexibility.

2:53 PM, February 28, 2008  
Blogger David Foster said...

Larry J..."conventional gasoline engines predate pacemakers by several decades"...true. But how often have pacemaker-wearers opened the hood and gotten within a couple of feet of a running engine? IIRC, electromagnetic field strength declines with the cube of distance, so the difference between close and not so close is a very significant one. If pacemakers are really that sensitive to fairly low-level signals, then it seems possible that there would have been isolated incidents that never got pieced together.

9:58 PM, February 28, 2008  
Blogger Dr. StrangeGun said...

"Why aren't pacemakers shielded more effectively?"

Because most of the modern models are set and monitored by a radio circuit and hence have not only the cardiac leads, but a communications antenna.

IIRC the trouble with microwaves and other devices of that manner (and high frequency) are verboten because the noise can actually breach the shielding in place... short wavelengths. I could also see a strong magnet causing problems not for physical issues but because of the current generated in the leads when it moves near them.

Whether or not the Prius is an issue will depend on the frequency used in it's motor controller, since I'm sure it's a switching PWM, and the frequency used to "talk" to the pacemaker unit.

(disclaimer: Dr. Strangegun is a doctor of wierd guns and oddball home engineering, not medical science... and really isn't a doctor at all)

8:32 AM, February 29, 2008  
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