Activity-sensing permanent internal pacemaker dysfunction during helicopter aeromedical transport

Study objectives: This study was designed to establish the frequency, magnitude, and possible etiologies of the dysfunction of activity-sensing internal pacemakers during helicopter aeromedical transport. Design: Two models of Medtronic Activitrax ® pacemakers were attached externally to healthy adult volunteers. Each volunteer then was loaded into the helicopter and subjected to a flight sequence. Pacemaker firing rates throughout this sequence were recorded. Setting: On separate days, Aerospatiale Dauphin and Twinstar helicopters completed a total of 23 flights. Type of participants: Four healthy adult volunteers, two men and two women, participated. Interventions: These included intra- and inter-flight threshold reprogramming and external magnet application. Results: The average preflight pacemaker rate of 65 beats per minute increased to an average in-flight rate of 105 beats per minute, which resolved to preflight rates on shutdown. This pattern was consistently extinguished with external magnet application. Conclusion: The effect of rotor motion and flight vibration on the rate-response of the Activitrax ® pacemaker is both predictable and easily preventable. Possible guidelines for the safe transport of these patients, using pacemaker reprogramming or external magnet application, are examined.