United States of America - The Food and Drug Administration has advised of the risk of serious injury or death to patients with implanted electrical leads who are exposed to diathermy treatments.

Reports have been received in which patients with implanted deep brain stimulators (DBS) died after receiving diathermy therapy. One patient received diathermy following oral surgery, the other for treatment of chronic scoliosis. In both cases, the interaction of the diathermy with the implanted device caused severe brain damage in the area where the lead electrodes were implanted.

There are three types of diathermy equipment used by physicians, dentists, physical therapists, chiropractors, sports therapists, and others: radio frequency (shortwave) diathermy, microwave diathermy and ultrasound diathermy. Shortwave and microwave diathermy, in both heating and non-heating modes, can result in serious injury or death to patients with implanted devices with leads. This kind of interaction is not expected with ultrasound diathermy. Electrocautery devices are not included.

Laboratory testing has shown that patients with any implanted metallic lead are at risk of serious injury when exposed to shortwave or microwave diathermy therapy. This is true even if the implanted device is not turned on, and even if the lead is no longer connected to an implanted system. Interaction of the diathermy energy with the implanted lead causes excessive heating in the tissue surrounding the lead electrodes. Insufficient testing has been done to determine whether there is a safe distance between the diathermy applicator and the implant system that might allow patients to be treated with diathermy without risk of injury.

It is recommended that shortwave or microwave diathermy should not be used on patients who have any implanted metallic lead, or any implanted system that may contain a lead. Both the heating and non-heating modes of operation pose a risk of tissue destruction.

Physicians and health care professionals should:

• Explain to the patient what diathermy is, and stress that they should not receive shortwave or microwave diathermy therapy.

• Be sure to ask the patient about possible implants before deciding to administer shortwave or microwave diathermy therapy. If the patient has an implanted lead or an implant containing a lead, diathermy therapy should not be used, even if the implant has been turned off. Examples of implanted systems that may contain a lead include cardiac pacemakers and defibrillators, cochlear implants, bone growth stimulators, deep brain stimulators, spinal cord stimulators, and other nerve stimulators.

• Do not administer shortwave or microwave diathermy therapy to a patient who has had an implant in the past unless you are absolutely certain that the implant and all leads in their entirety have been removed. Note that leads are often left implanted after the implant is removed.

Reference: Center for Devices and Radiological Health. http://www.fda.gov/cdrh/safety.html. 19 December 2002.