Medtronic, Inc.

Ben W Herberg

Hyun J Yoon

Michael L Ellingson

Jonathan D Edmonson

Todd Jon Sheldon

Wade M Demmer

James D Reinke

Paul R Solheim

Matthew J Hoffman

Robert A Betzold

Juliana E Pronovici

Piotr J Przybyszewski

Mark K Erickson

Christopher C Stancer

David E Manahan

Sandy K Wixon

Alison M Seacord

Joel Peltier

Sung-Min Park

Zhongping C Yang

Kevin R Seifert

Dina L Williams

Implantable medical systems enter an exposure mode of operation, either manually via a down linked programming instruction or by automatic detection by the implantable system of exposure to a magnetic disturbance. A controller then determines the appropriate exposure mode by considering various pieces of information including the device type including whether the device has defibrillation capability, pre-exposure mode of therapy including which chambers have been paced, and pre-exposure cardiac activity that is either intrinsic or paced rates. Additional considerations may include determining whether a sensed rate during the exposure mode is physiologic or artificially produced by the magnetic disturbance. When the sensed rate is physiologic, then the controller uses the sensed rate to trigger pacing and otherwise uses asynchronous pacing at a fixed rate.

Methods and implantable medical systems that implement exposure modes of therapy that allow for continued operation during exposure to a magnetic disturbance

Implantable medical devices automatically switch from a normal mode of operation to an exposure mode of operation and back to the normal mode of operation. The implantable medical devices may utilize hysteresis timers in order to determine if entry and/or exit criteria for the exposure mode are met. The implantable medical devices may utilize additional considerations for entry to the exposure mode such as a confirmation counter or a moving buffer of sensor values. The implantable medical devices may utilize additional considerations for exiting the exposure mode of operation and returning to the normal mode, such as total time in the exposure mode, patient position, and high voltage source charge time in the case of devices with defibrillation capabilities.

Methods and implantable medical devices for automatic entry to an exposure mode of operation upon exposure to a magnetic disturbance

A medical device lead is presented that includes an electrode assembly having a first electrode located near a distal end of the electrode assembly and a second electrode located near a proximal end of the electrode assembly. The electrode assembly also includes a conductive elongated coupler that is electrically coupled to the first electrode and capacitively coupled to the second electrode. At low frequencies and DC (e.g., during delivery of stimulation therapy), the capacitive coupling between the conductive elongated coupler and the second electrode presents a high impedance allowing little current to be redirected from the first electrode to the second electrode. However, at high frequencies (e.g., during an MRI scan) the capacitive coupling between the conductive elongated coupler and the second electrode presents a low impedance, resulting in a significant amount of induced current being redirected to the second electrode and dissipated into bodily fluid surrounding the second electrode.

Electrode assembly in a medical electrical lead

Techniques are described for controlling effects caused when an implantable medical device (IMD) is subject to a disruptive energy field. The IMD may include an implantable lead that includes one or more electrodes. The IMD may further include a first component having a parasitic inductance. The IMD may further include a second component having a reactance. In some examples, the reactance of the second component may be selected based on the parasitic inductance of the first component such that an amount of energy reflected along the lead in response to energy produced by an electromagnetic energy source is below a selected threshold. In additional examples, the parasitic inductance of the first component and the reactance of the second component are configured such that an amount of energy reflected along the lead in response to a frequency of electromagnetic energy is below a selected threshold.

Controlling effects caused by exposure of an implantable medical device to a disruptive energy field

An IMD may transition to an MRI mode automatically in response to detecting one or more conditions indicative of the presence of a strong magnetic field. Large static magnetic fields, such as those produced by an MRI device, may interact with the blood of a patient as it flows through the magnetic field to produce a voltage, a phenomenon referred to as the magnetohydrodynamic (MHD) effect. The voltage produced by the MHD effect is proportional to the strength of the magnetic field. As such, the voltage produced by blood flow in the strong magnetic field of an MRI device may result in a change in a characteristic of an electrogram (EGM). The IMD may detect the change in the characteristic of the EGM caused by the MHD effect and transition to operation in the MRI mode in response to at least the change in the EGM.

Magnetic field detection using magnetohydrodynamic effect

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Andover, MN, United States of America

Ben W Herberg