High-Power Electric Car Chargers Safe With Cardiac Devices

High-power chargers for battery powered electric vehicles (EVs) appear to be safe for use by patients with cardiac implantable electronic devices (CIEDs), a new study suggests.

High-power, direct-current (DC) chargers shorten the charging time compared with conventional alternating current (AC) chargers. CIEDs can be susceptible to electromagnetic interference (EMI), which may cause pacing inhibition, mode switching, inappropriate detection of tachycardia or therapy, or spontaneous device reprogramming.

"Electric vehicles, along with the charging stations, are potential sources of such EMI," lead author Carsten Lennerz, MD, of the German Heart Centre in Munich said during a moderated poster session.

He said electromagnetic fields are low inside the cabin of an EV, on the order of 2.1 to 3.6 microtesla (μT) for cables using moderate current (32A) and power (22kW). New, high power fast chargers using 400A current and delivering 350kW of power can create potentially clinically relevant electromagnetic interference for CIEDs.

In this report, they saw no evidence of risk for electromagnetic interference episodes among patients implanted with a variety of devices.

"We believe that no specific restrictions should be placed on their use, but we do recommend reasonable caution by minimizing the time spent in close proximity to the charging cables," Lennerz advised.

Their results were presented at the European Heart Rhythm Association in Barcelona and published simultaneously in EP Europace.

CIEDs and Car Chargers

To test whether high-power chargers are safe for people with CIEDs, Lennerz and colleagues enrolled in the study 130 patients (79% men) with pacemakers, implantable cardioverter defibrillators (ICDs), subcutaneous ICDs, and cardiac resynchronization therapy devices. Patients had a total of 53 models of devices from six manufacturers.

Excluded were patients with leadless pacemakers, lead malfunction, batteries with less than 3 months of longevity remaining, or an intrinsic heart rate greater than 120 beats/min.

Devices were programmed for permanent ventricular pacing to maximize EMI detection. ICD therapies were disabled except that tachycardia detection was active if applicable.

Patients had a median age of 59 years and had indications for anti-bradycardia therapy (35%) or anti-tachycardia therapy (65%). They performed 561 charges using six common models of high-power chargers, all capable of delivering 300 to 350kW, to charge four representative EVs capable of using these chargers and one additional vehicle capable of using full 350kW charging.

The investigators made magnetic and electric field measurements at various points in the charging apparatus. The maximum magnetic field strength at the upper part of the charging station was 77.9μT, and along the cable and at the connector, 38.7μT. The connector is the part at which the user makes contact with the device when connecting the cable to the EV.

Patients were asked to charge the EVs and were positioned so that the charging cables were over their CIEDs to mimic a worst-case scenario of EMI occurrence. They were monitored with 6-lead electrocardiograms to detect pacing inhibition or mode switching. After they charged the vehicles, the patients' CIEDs were interrogated to look for spontaneous reprogramming and for tachycardia.

"Solid Results"

There were no episodes of EMI detected by the CIEDs, and specifically, no inhibition of pacing in pacemakers or inappropriate detection of rapid arrhythmias by defibrillators that could lead to shock therapy.

So, among the 130 patients, the risk of EMI was 0/130 (95% CI, 0% - 2%), and on a per-charge basis, the risk was 0/561 (95% CI, 0% - 0.6%). Therefore, the use of high-power EV charging stations by such patients with CIEDs appeared safe.

The authors noted in the article that the high-power chargers use DC, whereas conventional household chargers use AC, which induces a magnetic field of 50Hz or 60Hz depending on the country. This field can induce harmonic electrical signals in wires and electrical devices. Their previous work indicated that "the use of conventional AC chargers did not result in clinical EMI."

They also note that given the large variety of CIED models in the study and the low number of each, they could not "exclude very rare events of EMI or that any specific device is at high risk for EMI." They recommended that as new battery and charging technologies come into use, they should be evaluated for the safety of patients with CIEDs.

Session co-moderator Jens Cosedis Nielsen, DMSc, PhD, co-director of the Department of Cardiology at Aarhus University Hospital, Aarhus, Denmark, told theheart.org | Medscape Cardiology that "the study was done systematically and properly and included a high number of patients and chargers," and the patients had a variety of forms of CIEDs.

"For current CIEDs and car types investigated, these results are valid and solid. Whether the data are valid for very old CIED types is unknown," he said. "Leadless pacemakers were not investigated in this study."

Cosedis Nielsen said he thinks it wouldn't be feasible for every charger manufacturer to test their apparatus for every type of CIED, "so they rather prefer a warning in their manuals." Although CIEDs are tested for EMI, he was unsure if and to what extent manufacturers disclose that information.

He said that in his clinic he has not seen any problems with interference between CIEDs and high-power EV chargers, so he is "confident that this is no significant problem" and thus would deter a patient with a CIED from buying an EV. Still, he reiterated Lennerz's advice that patients should minimize their time in close proximity to the charging cables.

The German Foundation of Heart Research supported the study. IONITY high power charging network provided the test vehicles and use of charging infrastructure at their test site. German Social Accident Insurance performed the electromagnetic field measurements. Lennerz has received travel and/or lecture honorarium support from Biotronik. Nielsen reports no relevant financial relationships.

European Heart Rhythm Association 2023. Presented April 17, 2023.

EP Europace. Published online April 17, 2023. Full text

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