Assessment of Electromagnetic Interference with Active Cardiovascular Implantable Electronic Devices (CIEDs) Caused by the Qi A13 Design Wireless Charging Board

Abstract

Electromagnetic interference is a concern for people wearing cardiovascular implantable electronic devices (CIEDs). The aim of this study was to assess the electromagnetic compatibility between CIEDs and the magnetic field of a common wireless charging technology. To do so the voltage induced in CIEDs by Qi A13 design magnetic fields were measured and compared with the performance limits set by ISO 14117. In order to carry this out a measuring circuit was developed which can be connected with unipolar or bipolar pacemaker leads. The measuring system was positioned at the four most common implantation sites in a torso phantom filled with physiological saline solution. The phantom was exposed by using Helmholtz coils from 5 µT to 27 µT with 111 kHz sine‑bursts or by using a Qi A13 design wireless charging board (Qi‑A13‑Board) in two operating modes "power transfer" and "pinging". With the Helmholtz coils the lowest magnetic flux density at which the performance limit was exceeded is 11 µT. With the Qi‑A13‑Board in power transfer mode 10.8% and in pinging mode 45.7% (2.2% at 10 cm distance) of the performance limit were reached at maximum. In neither of the scrutinized cases, did the voltage induced by the Qi‑A13‑Board exceed the performance limits.

Keywords: EMF risk assessment; Qi A13 design; defibrillator; electromagnetic interference; intermediate frequency magnetic fields; pacemaker; performance limits; wireless charging; wireless power transfer.

Figure 1

(a) Schematic diagram of the torso phantom. All implantation sites are indicated: 1. Housing: right-pectoral. Lead: atrium (RPA). 2. Housing: left-pectoral. Lead: atrium (LPA). 3. Housing: right-pectoral. Lead: ventricle (RPV). 4. Housing: left-pectoral. Lead: ventricle (LPV).The green area marks the unipolar induction area for the RPA implantation site (A_RPA). The orange area marks the unipolar induction area for the LPV implantation site (A_LPV). A_RPV and A_LPA are the unipolar induction areas of the implantation sites RPV and LPA. (b) Sensing mechanism of a bipolar lead. A differential (the housing is the reference electrode) voltage is measured between tip and ring electrode. (c) Sensing mechanism of a unipolar lead. A voltage is measured between tip and the reference (housing) electrode.

Figure 2

Results of the induced voltage for the homogenous exposure for (a) the bipolar lead, and (b) the unipolar lead. The linear fit to the measured values is indicated by the solid lines. The dashed lines indicate the extrapolation of the linear fit to the ranges where no induced voltages were measured due to the operation range of the used differential amplifier of the measurement system.

Figure 3

Pinging sequence recorded during pinging mode of the Qi-A13-Board. The amplitude is normalized to one.

Figure 4

The measured magnetic flux density vs. the coordinates x and y on the plane is shown for the power transfer mode at two distances (2 cm (a) and 10 cm (b)) and for the pinging mode at two distances (2 cm (c) and 10 cm (d)). The missing values in the plot of the power transfer mode at 2 cm (a) are caused by the housing of the AVID-Receiver.

Figure 5

(a) Torso phantom and Qi-A13-Board (pinging mode) on the lateral wall; (b) AVID-Receiver close to the edge of the Qi-A13-Board. If the AVID-Receiver was moved further over the edge the connection was interrupted.

Figure 6

The percentage portion of the performance limits of ISO 14117 contextualized with the most EMI affecting parameters: the four implantations sites, the two lead types and the two operating modes of the Qi-A13-Board. Additionally the attenuation of the induced voltage at 10 cm distance is presented (compare red and blue markers).