EMI risk for patients with pacemakers and defibrillators?

Battery-powered electric vehicles and their charging stations are a potential source of electromagnetic interference (EMI) for patients with cardiac implantable electronic devices (CIEDs). The new “high power” charging stations have the potential to generate strong electromagnetic fields and induce EMI in CIEDs. Their safety has now been evaluated in a study.

Implantable electronic cardiac devices (CIEDs), including pacemakers (PMs), implantable cardioverter defibrillators (ICDs), and cardiac resynchronization therapy (CRT) systems, are the primary or adjunctive treatment for arrhythmias or heart failure and are becoming increasingly popular [2–4]. Previous studies have shown that CIEDs are susceptible to electromagnetic interference (EMI), which can lead to spontaneous reprogramming of the device as well as mode switching, inhibition of pacing, or inappropriate tachycardia detection/therapy [5–8].

The electromagnetic field generated by an electrical device has the potential to cause EMI. It may induce current in the CIED circuits that can be detected by the CIED and falsely attributed to intracardiac signals. The risk of EMI depends on the strength of the electric and magnetic field. The magnetic field itself is proportional to the electric current source according to Ampere’s law. The higher the charging current, the stronger the magnetic field and the higher the EMI risk. The underlying principle: the speed of rotation of the motor is proportional to the voltage applied and the torque is proportional to the current drawn. Car manufacturers optimize current and voltage to maximize power, speed and torque. The vehicle design represents a compromise between maximum permissible current and voltage. Electric motors used in fully electric cars (e-cars) are very powerful and have an output of up to 500 kW.

High power chargers have the potential to cause EMI

One of the barriers to the adoption of battery electric vehicles (BEVs) has been the long charging time required. However, this problem has been addressed with the development of high-capacity charging stations that deliver higher amperage to quickly charge a BEV battery. The newer high-performance chargers are capable of charging BEVs faster; they use direct current and can deliver 300-350 kW. Because the charging current is directly proportional to the magnetic field, the high-power chargers have the potential to cause clinically relevant EMI [9,10].

Electromagnetic interference detection algorithms and device shielding reduce the risk of clinical EMI, but it is still important to identify and evaluate new potential EMI sources [11,12]. This is because recent studies on the risk associated with the Apple iPhone 12 (and other products containing magnets) showed that new technologies can pose such a risk to patients and that this is a significant source of anxiety or uncertainty [13,14]. Therefore, the objective of a recent study was to evaluate the potential EMI risk posed by these high-power chargers [1].

Electric cars with high power consumption and implantable electronic devices

Four BEVs were used for the study (Porsche Taycan Turbo, VW ID3 pro performance, Tesla Model 3 Performance and Audi E-tron 55 Quattro), which can be charged at high power. In addition, an IONITY test vehicle capable of 350 kW charging was used. These BEVs were selected because they are all-electric and compatible with the use of high-performance chargers. Six common high-power charging stations with a capacity of 300-350 kW were used. Since the current delivered is inversely proportional to the battery state of charge at the end of each test day, each BEV was driven until the battery charge was <20%. The actual current delivered during each charge was measured for each BEV during each charge. The measurements of the electric and magnetic fields were made along the charging cable and at the charging pole and were given as RMS values.

A total of 130 patients with a mean age of 59 ± 18 years (79% male) underwent 561 batches. CIEDs tested included 45 PMs (35%) and 85 ICDs (65%), of which 33 were S-ICDs, representing 25% of ICDs. The indication of the devices was primary prevention of sudden cardiac death in 38%, secondary prevention of sudden cardiac death in 27%, AV block in 25%, and sinus node dysfunction in 10%. A wide range of devices were represented in the study, including 53 different devices from six different manufacturers. Similarly, a wide range of electrodes were included in the study.

Electromagnetic interference evaluation

The maximum magnetic field (H-field) along the charging cable and at the charging system connector (connection to the BEV) was 38.65 µT RMS and at the charging station (at the point where the charging cable leaves the charging unit) was 77.9 µT (Fig. 1) [1]. The maximum electric field (E-field) along the charging cable was 74.33 V/m RMS and 281.7 V/m peak. The delivered charge for each vehicle varied depending on the battery state of charge; for the Porsche Taycan, Tesla Model 3, and VW ID3, the delivered charge was inversely proportional to the state of charge, but for the Audi E-tron and the IONITY test vehicle, the delivered charge was independent of the state of charge (Fig. 2) [1]. The delivered charge was highest for the IONITY test vehicle at 350 kW, followed by the Tesla at 190 kW at a state of charge <20%.

No EMI episodes were detected; specifically, there were no episodes of pacing inhibition, oversensing, erroneous tachycardia detection, or spontaneous reprogramming of the device. Thus, the risk of EMI is 0/130 (95% CI 0%-2%) for a patient-based analysis and 0/561 (95% CI 0%-0.6%) for a fee-for-service analysis.

Take-Home Messages

Various high-power charging stations and advanced battery-powered vehicles were used by supervised CIED patients.
No electromagnetic interference and no spontaneous reprogramming, pacing inhibition, or inappropriate tachycardia detection were detected.
The use of the new high-power charging technology appears to be safe for patients with CIEDs, and no specific restrictions should be placed on its use.

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