Safety Alert

For Physicians

CONTRAINDICATION: Do not use shortwave diathermy, microwave diathermy or therapeutic ultrasound diathermy (all now referred to as diathermy) on patients implanted with a neurostimulation system. Energy from diathermy can be transferred through the implanted system and can cause tissue damage at the location of the implanted electrodes, resulting in severe injury or death.

Diathermy is further prohibited because it can also damage the neurostimulation system components resulting in loss of therapy, requiring additional surgery for system explantation and replacement. Injury or damage can occur during diathermy treatment whether the neurostimulation system is turned “on” or “off.” Advise your patients to inform all their health care professionals that they should not be exposed to diathermy treatment.

May 16, 2001

Medtronic Neurological is issuing this Safety Alert to all physicians, patients and facilities involved with its implanted neurostimulation systems, which include:

Activa® Systems for deep brain stimulation (DBS)
Spinal Cord and Peripheral Nerve Stimulation Systems
InterStim® Therapy (Sacral Nerve Stimulation)
Enterra® Therapy
Dynamic Graciloplasty

DO NOT use or prescribe shortwave diathermy, microwave diathermy or therapeutic ultrasound diathermy (all now referred to as diathermy) for patients implanted with any type of Medtronic neurostimulation system. Use of diathermy on patients with any implanted neurostimulation device can cause heating at the tissue/stimulation electrode interface, which under certain circumstances can result in permanent tissue or nerve damage. Such tissue damage could lead to permanent injury or even death. The exact nature of the tissue or nerve damage depends on the location of the stimulation electrodes implanted in the patient (e.g. brain, spinal cord, sacral nerve, stomach), and the extent of the exposure to diathermy treatment.

This contraindication applies regardless of where the diathermy treatment is targeted on the patient’s body in relation to the implanted stimulation system.
This contraindication applies regardless of whether it is used to deliver heat or no heat.
This contraindication applies regardless of whether the Medtronic neurostimulation system is turned “on” or “off”.
This contraindication applies if any individual components of the neurostimulation system remain implanted in the body.

Medtronic is issuing new labeling for its neurostimulation systems using the contraindication language printed above. A patient-friendly version of the above contraindication language will appear in patient manuals and materials. The FDA has been notified of this issue and of Medtronic’s notification plans.

What are shortwave diathermy, microwave diathermy and therapeutic ultrasound diathermy treatments?
Diathermy treatments are used by a variety of health care professionals, including physical therapists, nurses, chiropractors, dentists, sports therapists, and others. Health care professionals may refer to diathermy using the term “deep heat” or similar terms. Diathermy means deep heat, but these devices may also be used in a way that causes little or no heating. Diathermy does not include ultrasonic imaging or electrocautery devices. Diathermy that uses these forms of energy (shortwave, microwave or ultrasound) can cause permanent nerve or tissue damage in patients with a neurostimulation system even if the diathermy is set at power levels that do not cause deep heating.
Diathermy (d_´-a-thur-m_) are treatments that deliver energy to treat specific areas of the body. These treatments are typically used for the following purposes:

relieve pain, stiffness and muscle spasms
reduce joint contractures
reduce swelling and pain after surgery
promote wound healing

The contraindication with implantable neurostimulation devices applies to all forms of diathermy.

Risk to Patients:
Medtronic has received two case reports of patients implanted with deep brain stimulation systems who received shortwave therapy (diathermy), one following oral surgery, the other for treatment of chronic scoliosis. In both cases, the shortwave energy caused severe and permanent brain damage in the area of the lead electrodes implanted in the brain. Both patients remain in a comatose condition since receiving shortwave diathermy.

As a result of the above case reports, Medtronic conducted tests on a neurostimulation system with one type of shortwave diathermy device. The tests found that the energy generated by the shortwave type of diathermy will cause heating well above the temperatures required for tissue destruction.

Due to the widespread use of diathermy for a variety of therapeutic treatments in the health care community, it is reasonable to assume that all patients with implanted neurostimulation systems can be at risk of exposure to diathermy therapy.

Impact on Neurostimulation Systems:
Please note that the permanent nerve or tissue injury is not caused by a device malfunction. Rather, it is caused by the interaction of two devices (neurostimulation system and diathermy machine) when they are working properly. Medtronic has previously cautioned against diathermy, as it poses a risk of damage to the implanted device. Although the testing subsequent to the reported events did not show damage to the Medtronic device, Medtronic continues to believe that diathermy of any type poses a real risk of damage to implanted neurostimulation devices and should be avoided. Other types of diathermy equipment have not been tested, and the specific effects of any individual diathermy system on the neurostimulation systems are unknown. Routine interrogation of the implanted neurostimulation device can ascertain its functional integrity.

If you have any questions related to this Safety Alert or any other safety issues regarding Medtronic’s implantable neurostimulation devices, please contact Medtronic’s Technical Service line at 1-800-328-0810. Please refer to the technical manuals provided with your Medtronic products to review the entire list of other contraindications, precautions, and warnings regarding the safe use of these devices.