Progress | vigilant! These electronics can interfere with cardiovascular implants!

*For medical professionals only

Cardiovascular implant devices (CIEDs) have a special magnet pattern, such as the magnet mode of pacemakers and implantable cardioverter defibrillators, to facilitate the setting of the device to a standardized mode, mainly for ICD tachycardia detection and treatment, as well as non-synchronous pacing pause of pacemakers.

In clinical practice, a special magnet pattern can be triggered by applying a special magnet from the outside, which exhibits a maximum field strength greater than 100 Gaussian (G) at a distance of 30 mm. However, according to the International Organization for Standardization standard 14117, the minimum field strength required for CIED to trigger the magnet mode is 10G. Below this field strength, mode switching is not triggered.

Recently, some scholars have reported the interaction of the smartphone iPhone 12 Pro Max (containing magnets) with many CIED. In everyday environments, where mobile phones are often placed in the pockets of shirts or jackets, CIED has the potential to penetrate a magnetic field with a field strength of more than 10G generated by mobile phones. Therefore, it is of great clinical significance to strengthen the understanding of the magnetic field strength of electronic products and the resulting safety distance.

Recently, the journal Circ Arrhythm Electrophysiol published a study that quantified the CIED's 10G dividing line using a dedicated magnetic field map, which can be measured about 20mm from the back of the phone. Let's take a look!

Introduction to the study

The researchers investigated the magnetic field strength of the Apple AirPods Pro and its wireless charging case, Microsoft Surface Pen and Apple Pen (second generation) and compared it to the iPhone 12 Pro Max.

Due to the three-dimensional (3D) nature of the magnetic field and its strong intensity gradient near the permanent magnet, a three-dimensional magnetic field plot with resolutions in the millimeter range is required to reliably assess the risk of inadvertently triggering CIEDs magnet patterns.

Draw a three-dimensional map at a resolution of up to 2mm compared to the recently announced setup by the U.S. FDA, which includes manually moving and rotating a single single-axis magnetic field sensor and offering a resolution of 10mm.

The magnetic field mapr used by the researchers has 64 triaxial magnetic sensor chips (AK09970N).

The mapper is mounted on a custom automated 3D platform that allows configurable volumes to be drawn above the device.

The minimum in vitro safety distances of 5 different ICDs (Boston Scientific: Inogen, Teligen, Cognis, Medtronic: Protecta, Viva Quad) from two manufacturers were mapped.

The 10G contours in the figure are displayed in augmented reality along with a 3D view of each device. Highlights areas where magnetic fields exceed 10 G, ciED should not penetrate.

The study found:

Of all the Apple products shown, the furthest point measured to 10G strength is about 20mm off the surface, while the Microsoft Surface Pen is at 29mm. In vitro measurements are shown in the figure.

The handheld electronic device (PED) tested triggered a magnet inversion mode at a distance of 8 to 18mm.

In addition to the iPhone 12, PED also has magnetic induction, so it is possible to suppress CIED performance (lifesaving therapies).

In clinical practice, because patients often put these PED in the pocket of the chest, magnetic field and in vitro measurements confirm that the minimum safety distance of patients with CIED > 20mm. This work provides a high-resolution magnetic field map that depicts the associated characteristics of portable electronic devices.

In addition, the study highlighted two other product categories like the iPhone 12 that affect CIED (headphone cases and tablet pens). Although Apple's website does not mention the second-generation Apple Pencil in its list of devices that can cause CIED magnetic interference, the study shows that the second-generation Apple Pencil produced a 10G magnetic field, causing CIED to interact at a distance of 8mm. Further research is needed to see if other PED, such as smartwatches or e-cigarettes, will also affect CIED.

Research Review

Previous studies have confirmed that the iPhone 12 has a magnetic force strong enough to affect the ICD and put the pacemaker in abnormal mode (Heart Rhythm 2021; 18:1040）。

The new study evaluated other portable electronic devices and found that three other categories of devices (Apple AirPods Pro and its wireless charging case, Microsoft Surface Pen, and second-generation Apple Pen) also have a magnetic field strong enough to have an impact on CIED. The minimum trigger distance per device varies from 8mm to 18mm.

Therefore, as with the iPhone 12, these devices should not be placed near the front chest position or chest pocket of a patient placed in a CIED.

source:

Magnetic Field Measurements of Portable Electronic Devices: The Risk Inside Pockets for Patients With Cardiovascular Implantable Devices.Circ Arrhythm Electrophysiol. 2022 Mar;15(3):e010646. doi: 10.1161/CIRCEP.121.010646.