An intervenor in Docket No. 37248, AEP’s application for a CCN in Childress County, states that the proposed project “would directly affect the ability of the pacemaker to work.” She filed a letter from Biotronik, the manufacturer of her Protos DR/CLS pacemaker. The intervenor lives near a substation and an existing 69 kV transmission line, but the existing line is proposed to be increased to a 138 kV transmission line.
The Biotronik letter states that electromagnetic interference (EMI) with pacemakers is a complex issue. Biotronik states that it is not able to define an exact EMI level to avoid because (1) there is an infinite number of field compositions (radio frequency and power combinations); (2) the effect of the field on the pacemaker system will vary with patient orientation in the field; and (3) placement of every pacemaker within a patient’s anatomy is unique, which means the level of shielding is unknown.
The letter addresses the effects that could happen to the patient or implant if exposed to strong EMI. The pacemaker’s response depends on the EMI characteristics, proximity to the interference, available shielding, and the pacemaker’s sensing characteristics and polarity.
Biotronik describes some complications that could result from strong EMI interference:
- Inhibition of pacing for a slower than normal heart rate can occur due to electrical noise sensed by the device. It is possible for intermittent electrical noise to be mistaken as normal heart beats, which will prevent the device from pacing the heart if the patient’s rhythm becomes dangerously low. It is possible for the patient to lose consciousness if this occurs.
- Noise mode pacing, which means the device will pace asynchronously in the presence of high-frequency electrical noise, rather than timing the pacing based on the patient’s intrinsic heart activity.
- Devise reversion to back-up mode, which means the device will still operate in a safe program, but it will not operate with the specific parameters prescribed by the patient’s physician until it is checked and reprogrammed in the doctor’s office.
Biotronik states that the best protection for patients with its pacemakers is to maintain the farthest possible distance from sources of EMI in order to avoid any possible interaction with the implanted device. In general, Biotronik states, a higher power source will produce greater EMI compared to a lesser power source at the same frequency.
Biotronik’s web site includes a patient manual that advises patients to avoid high-voltage transmission lines because they may emit EMI signals that could affect normal pacemaker operation.