The effect of 50 Hz external electrical interference on implanted cardiac pacemakers

Area of Science:

• Biomedical Engineering
• Cardiology
• Electrophysiology

Background:

• Implanted cardiac pacemakers are crucial for managing bradyarrhythmias.
• Understanding pacemaker susceptibility to external electromagnetic interference is vital for patient safety.
• Previous studies have explored various interference sources, but controlled testing methods for 50 Hz AC interference require further investigation.

Purpose of the Study:

• To evaluate the effects of injected 50 Hz alternating current (AC) on the function of VVI pacemakers.
• To determine the current thresholds at which pacemakers exhibit interference or reversion modes.
• To assess the safety and reproducibility of using current injection as a method for testing pacemaker sensitivity.

Main Methods:

• 18 patients with implanted unipolar VVI pacemakers were subjected to injected 50 Hz AC (0-600 microA) via surface electrodes.
• Pacemaker response, including reversion to interference mode and pacing irregularities, was monitored.
• Interference voltage was measured in 10 additional patients using temporary pacing catheters.
• Factors influencing sensitivity, such as electrode placement, patient posture, and respiration, were analyzed.

Main Results:

• Most VVI pacemakers reverted to interference mode within a current range of 29-250 microA.
• Irregular and inappropriate pacing occurred just below the reversion current threshold, varying from 27-246 microA.
• Pacemaker sensitivity was influenced by electrode location, patient posture, and deep inspiration.
• Measured interference voltage also varied with posture and respiration.

Conclusions:

• Injected 50 Hz AC can safely and reproducibly test VVI pacemaker sensitivity to external interference.
• Pacemaker reversion and irregular pacing occur at specific, patient-dependent current levels.
• Patient factors like posture and respiration significantly impact pacemaker response to interference.