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In order to evaluate if antitheft devices commonly designed as electronic article surveillance (EAS) systems can be dangerous for pacemaker patients, in vitro and in vivo studies were made in close cooperation between a pacemaker center and an EAS designer. Three types of EAS radiation including radiofrequency, magnetic, and pulsed electromagnetic fields were applied to various pacemakers. The in vitro study consisted of exposing to the EAS fields 28 pacemakers connected to unipolar leads. Radiofrequency fields and pulsed electromagnetic fields evoked minor effects and no prolonged inhibitions. When exposed to magnetic fields, most of the pacemakers switched to "fixed rate" pacing, but inhibitions were observed in 13 pacemakers exposed to 300 Hz, and in 14 pacemakers exposed to a 10-kHz magnetic field when they were moved at cardiac frequencies within the fields. The in vivo study was made on 32 volunteers treated by 26 different pacemakers: 22 single chamber and ten dual chamber. All patients had been monitored in the pacemaker clinic and pacemakers were working well. Radiofrequency and pulsed electromagnetic fields did not affect the pacemaker function. Magnetic interference evoked prolonged inhibition of seven out of the ten dual chamber pacemakers, causing brief asystole in patients being continually paced. None of the dual chamber pacemakers incorporated "safety stimulation intervals" after ventricular blanking. The EAS artifact was sensed after the ventricular blanking causing a cross-talk ECG pattern. No reprogramming was induced by the electromagnetic fields. This experience demonstrates that certain EAS may be dangerous for pacemaker patients. Following this cooperative study a pacemaker safe EAS circuit delivering short bursts of magnetic fields has been designed.

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