Thirty-five patients fitted with 16 different pacemaker models (from 6 manufacturers) were exposed to 50 Hz electric fields up to a maximum of 20 kV/m. Four different response patterns were encountered: (1) normal sensing and pacing in all Medtronic and some Vitatron units; (2) reversion to the fixed (interference) rate in all Telectronics, all Pacesetter, some Vitatron and CPI units; (3) slow and irregular pacing in one CPI and in all Cordis units; (4) mixed behavior over a critical range of field strengths in which slow and irregular pacing preceded reversion to fixed-rate, in some Telectronics and Pacesetter units. The field strengths required to induce such behavior varied from unit to unit and from model to model, with Telectronics being the most sensitive. In general, the interference threshold depended on the magnitude and distribution of induced body current relative to the pacemaker as well as field strength and thus varied with patient height, build and posture. While only a small proportion of pacemaker patients are likely to encounter electric fields strong enough to interfere with pacemaker behavior, this possible hazard should be recognized.

Adult↗

PubMed1983

Stable iodine.

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Humans↗

PubMed1982

Effects of high-intensity power-frequency electric fields on implanted modern multiprogrammable cardiac pacemakers.

The effect on an implanted, multiprogrammable pacemaker of power-frequency (50 Hz) electric fields up to an intensity (unperturbed value measured at 1.7 m) of 20 kV/m were assessed in ten paced patients. Radiotelemetric monitoring of the electrocardiogram allowed supervision of the electrocardiogram throughout exposure to the alternating electric field. Displacement body currents of up to 300μA were achieved depending on the position and height of the patient. None of the pacemakers was inhibited, triggered or reverted to fixed rate operation during the exposure. The programmable functions, programmability or output characteristics were not affected. Small changes in cardiac rate and rhythm elicited the correct pacemaker responses. Unlike earlier models of pacemaker, this modern implanted pacemaker, which represents `the state of the art', is not affected by 50 Hz electric fields likely to be encountered when standing underneath power lines.

Aged↗

PubMed1982