Recent Trends and Developments in Passive Component EMI Filters for Active Implantable Medical Devices

摘要

Active Implantable Medical Devices (AIMDs) include cardiac pacemakers, implantable cardioverter defibrillators (ICDs), neuromodulators, drug pumps, and the like. There has been an explosion of new emitters over the last few years that the patient is exposed to. These include cellular telephone amplifiers, RFID readers, keyless entry systems, and various medical diagnostic, therapeutic and imaging procedures such as MRI. Accordingly, National and International Standards for EMC compliance of AIMDs are evolving to become more comprehensive. There is a need for higher performance passive component EMI filters to meet these new challenges. This paper reviews the design trends in lead based bandpass and AIMD housing lowpass feedthrough EMI filters. Included are new electrode based filters that are designed to be installed at or near the point where implanted lead wires contact body tissue (the Distal Tip). These new Distal Tip bandstop filters consist of a resonant L-C circuit and are designed for biocompatibility and long-term reliability. The new filters significantly reduce the chance for AIMD electronics to malfunction due to the electromagnetic interference (EMI) produced by MRI systems. More importantly, the new Distal Tip filters raise the system impedance which reduces the currents induced in AIMD lead wires curing MRI imaging thereby reducing or eliminating problems associated with lead wire overheating.