Montreal: Cardiac device wearers to limit their exposure to high voltage power
lines, says Dr. Katia Dyrda of Montreal Heart Institute and University
of Montreal. Her research into electromagnetic
interference (EMI) was conducted in response to public concerns about
bicycle routes and walking paths under high voltage power lines (230 kV
and more) and whether these are safe for patients with cardiac devices.
These high electric fields are also encountered in utility substations
where employees who bring up power lines, conduct maintenance or work
within the buildings (cleaners, for example) may be exposed.
“High electric fields may interfere with the normal functioning of
cardiac devices, leading to the withholding of appropriate therapy
(anti-bradycardia pacing, for example) or to the delivery of
inappropriate shocks. The International Organization for Standardization
says pacemakers and ICDs should give resistance up to 5.4 kV/m (for 60
Hz electric fields) but electric fields can reach 8.5 kV/m under high
voltage power lines and 15 kV/m in utility substations,” Dr. Dyrda said,
noting that “there is a lot of interest in using the areas under power
lines as bicycle paths or hiking trails because it's essentially free
space. But patients and the medical community want to understand the
risks. There are no recommendations from device manufacturers about
power lines or higher electric fields.”
The study exposed 40 cardiac devices (21 pacemakers and 19 ICDs) from
five manufacturers to electric fields up to 20 kV/m in a high voltage
laboratory. The devices were mounted in a saline tank at human torso
height. Devices were set up as both left and right sided pectoral
implants. The researchers found that when pacemakers were programmed to
nominal parameters and in bipolar mode they were immune to EMI up to 8.6
kV/m. But when programmed to higher sensitivity levels or in unipolar
mode, the EMI threshold decreased to as low as 1.5 kV/m in some devices.
When programmed to nominal parameters, all ICDs were immune to EMI up
to 2.9 kV/m. There was no difference in EMI thresholds between left and
right sided implants.
“There is no significant concern for patients with pacemakers
programmed in the usual configuration (nominal settings, in bipolar
mode). For the minority of patients with devices in unipolar mode or
with very sensitive settings, counselling should be given at
implantation or at medical follow-up,” Dyrda explained. “There is no
need for patients with a pacemaker or ICD to avoid crossing under high
voltage power lines (> 230 kV) but patients should avoid staying in a
stationary position underneath them. Passing near pylons rather than
between two pylons mitigates exposure to the electric field because the
wires sag in the middle and the field is higher at this location.”
Dyrda emphasised that this advice does not concern distribution lines
(lines delivering electricity to homes), as the 60 Hz electric field
that they generate is very low, adding that “Patients ask us if they
should avoid driving on roads that cross under high voltage power lines.
The answer is no. If you're in a vehicle you are always protected
because your car acts as a Faraday cage and shields you automatically.”
Employees with a pacemaker or defibrillator should tell their
employer so that their safety at work can be carefully evaluated, Dyrda
urged. “Our study tested the effect of electric fields up to 20 kV/m and
the results can be used to assess individual risks depending on
exposure levels during specific tasks and the type and model of cardiac
device. This may lead to job adjustments or, more rarely, to a job
change.”
Source: Adapted from materials provided by the European Society of Cardiology Press Office