Electromagnetic Interference

OVERVIEW

• electromagnetic interference can affect the function of implanted electronic devices such as pacemakers and ICDs

CAUSES

• diathermy (monopolar & bipolar)
• mobile phones (don’t place over pacemaker)
• MRI
• shivering
• fasciculations
• alterations in heart size
• positive pressure ventilation
• peripheral nerve stimulators
• TENS machine
• defibrillation

EFFECTS ON PACEMAKERS AND ICDs

• inappropriate triggering or inhibition of output
• asynchronous pacing
• reprogramming
• damage to device circuitry
• pacing wires may acts as aerials and cause heating of endocardium

PREVENTION

• use bipolar diathermy
• if conventional diathermy required → position plate so that most of current passes away from the pacemaker, use short, sharp bursts and watch SpO2 or art line.
• ensure all devices are not in the same vector as the pacemaker current (between pacemaker and heart)
• if reason for pacemaker severe heart failure where loss of AV synchrony may precipitate haemodynamic compromise -> have a telemetric programmer and cardiac technician close @ hand
• keep lithotripter at least 6 inches away from pacemaker (should be timed with ECG and rate modulation deactivated)
• if have to defibrillate keep pads as far from pace maker as possible
• avoid sux c/o fasciculations (if used in a patient with a sensing mode activated -> use defasciculating dose of NDNMBD)
• avoid using defibrillation if at all possible (high level of EMI) -> if required use AP pad configuration and keep pad’s 10cm away from pacemaker

MAGNETS

• no longer recommended to place magnet over pacemakers, only applicable to older non reprogrammable pacemakers
• placement of a magnet would default mode to an asynchronous mode or a fixed rate
• all modern pacemakers are reprogrammable

MANAGEMENT OF PACEMAKER MALFUNCTION

• get help
• remove electromagnetic interference
• precordial thumps (percussive pacing)
• isoprenaline
• adrenaline
• transthoracic external pacing (capture around 80mA)
• trans-venous pacing
• transoesophageal pacing

References and Links

• CCC — Pacemakers