Pacemaker Magnet Response VVI — FRCA Final MCQ

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ModerateAnaesthetic Equipment & SafetyPacemaker Magnet Response VVIFRCA Final

A 68-year-old man (ASA III) has a permanent pacemaker (VVI mode) for complete heart block. He requires a hip replacement. The magnet response of a VVI pacemaker converts it to:

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Correct answer: B — VOO mode (asynchronous pacing at a fixed rate)

Placing a magnet over a pacemaker activates the 'magnet response' – this converts most pacemakers to an asynchronous mode (ignoring sensed signals). For VVI pacemakers: magnet converts to VOO mode (ventricular pacing at a fixed rate, typically 65-85 bpm depending on manufacturer, with no sensing). For DDD: converts to DOO. This ensures continuous pacing output regardless of electromagnetic interference from diathermy. The magnet should be removed after diathermy use to restore normal sensing function. Note: magnet response in ICDs is different – it disables tachycardia detection/therapy but does not affect pacing.

Reference: Association of Anaesthetists – 2023 – CIEDs perioperative management; RCOA – 2023 – Equipment