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Electromagnetic Interference (EMI) in the Workplace

 

Description

Boston Scientific adheres to the Association for the Advancement of Medical Instrumentation (AAMI) standards for testing of implantable pacemakers, implantable cardioverter defibrillators (ICD), or heart failure devices (cardiac resynchronization therapy-defibrillator [CRT-D] or -pacemaker [CRT-P]) in the presence of EMI. As such, these devices incorporate protection mechanisms (filters) to ensure normal operation in the presence of most operating equipment in home, public and work environments. However, some workplace environments contain equipment that may produce large levels of electromagnetic energy and subsequently interfere with the operation of the implanted device.

 

While the majority of workplace environments will not adversely affect implantable device operation, EMI of significant strength may impact the performance of the implanted device, and could potentially lead to the following temporary device responses:

     Figure 1. Reference levels for general public exposure to time-varying and magnetic fields. 

Device response

ICDs / CRT-Ds

Pacemakers / CRT-Ps

Asynchronous pacing

Inhibition of pacing (pacing therapy not provided when needed)

Inhibition of tachyarrhythmia therapy (shock therapy not provided when needed)

 

Inability to communicate with the device

Inappropriate shocks (shock therapy provided when not needed)

 

Deactivation of shock therapy

 

Trigger ventricular pacing at Maximum Tracking Rate

Trigger the End-of-Life indicator

 

 

The impact to device function is typically temporary; if the employee (patient) moves away from or turns off the EMI source, the implanted device resumes its normal mode of operation. In rare instances, the impact to the device may be permanent such as memory corruption or reversion to Safety Mode operation.

 

Workplace environmental EMI testing

Because EMI has the potential to adversely affect implanted device performance, some employers may request an environmental EMI assessment (also called site surveys) of their workplace to assist in determining if the patient with an implantable device can return to work. Allowing a patient to resume work is a medical decision, and must be made cooperatively by the physician, the employer and the patient; Boston Scientific cannot provide recommendations as to whether or not the patient should return to work.

 

 

If an environmental assessment of the workplace is requested, the EMI testing consultant may conduct a site survey of the entire facility, or may conduct testing on a single piece of equipment. These site surveys should be conducted in accordance with a broad range of electromagnetic specifications and regulations, and will help identify EMI sources that may interact with the patient’s device. While we can suggest site survey agencies and provide technical information to professional testing consultants regarding operation and specifications of our devices, Boston Scientific does not conduct or provide reimbursement for site surveys. Furthermore, Boston Scientific recommends that only trained individuals employed by professional testing agencies perform workplace environmental EMI assessments. Boston Scientific makes no representations as to the quality or capability of the consultants that an employer may appoint to conduct the survey.

 

 Site survey considerations

Table 1 lists the EMI field measurements of interest with respect to evaluating potential interaction of certain workplace equipment with Boston Scientific implantable devices.

 

Table 1.  EMI Field Measurements of Interest for Evaluating Boston Scientific CRM Implantable Devices

 

Description

Frequency

Frequency Range

Unit of Measurement (RMS*)

 

E-field strength

Low

Below 1 kHz

 

Volts / meter (V/m)

High

500 kHz to 6 GHz

 

H-field strength

DC (Static)

0 Hz

 

Gauss (G), Tesla (T), or Amperes (A) / meter (A/m)

Low

0.1 Hz to 3 kHz

Power density

High

10 MHz to 300 GHz

Watts (W) / meter^2 (W/m^2)

*RMS (Root Mean Square) is a method of signifying the amplitude of an electrical characteristic such as magnetic or electric field strength

E-field is a static or dynamic electric field

H-field is a static or dynamic magnetic field

 

The EMI testing consultant will typically obtain the peak measurements for the frequency bands of interest (as listed above) and compare to reference levels found in industry standards such as the International Commission on Non- Ionizing Radiation Protection (ICNIRP) as shown below in Figure 1.

 

While the ICNIRP guidelines state that “compliance with the present guidelines may not necessarily preclude

interference with, or effects on, medical devices such as…pacemakers and defibrillators…,” under ordinary circumstances, it is Boston Scientific’s belief that exposure to electromagnetic field strengths below the reference levels should not interfere with the operation of Boston Scientific implantable devices. Please note that the effects of EMI can vary based on the physical positioning of the implanted pulse generator and lead system within a patient's body; therefore, safe operation at the levels listed above are neither guaranteed nor absolute.

 

 1“Guidelines for Limiting Exposure to Time-Varying Electric, Magnetic, and Electromagnetic Fields (up to 300 GHz),” Health Physics, Vol. 74, No. 4, 1998,

494-522.

 

June 23, 2006                                  ©2006 Boston Scientific Corporation Fact Sheet                          Page 2 of 2