Magnet Effects on Pacemakers

All pacemakers respond to a magnet by switching to an asynchronous pacing mode at a programmed atrioventricular (AV) delay and a fixed magnet rate depending on the manufacturer, device model, and the status of the battery. The programmed mode DDD switches to DOO, VVI switches to VOO, and AAI switches to AOO. The rate response feature is switched to 'OFF' on magnet application in pacemakers. In biventricular pacemakers, both the right and left ventricles continue to be paced in the above modes with magnet application so long as the device is at or above elective replacement indicator "ERI". However, if  below ERI voltage, this response is unpredictable. If magnet application on a pacemaker site does not produce a response on the surface ECG pacing rate or mode, the magnet may be repositioned. If no change is still observed, the following reasons may apply: (i) a depleted pacemaker battery; (ii) the pacemaker is programmed to ignore the magnet (St. Jude, Boston Scientific, and Biotronik synchronous mode); (iii) the magnetic field does not reach the device, as in the case of those with deeper (abdominal or sub muscular) implants or in very obese patients; (iv) end of battery life "EOL" or lower battery life. Additionally, with Biotronik pacemakers in a synchronous mode, if your own heart rate is higher than the lower programmed rate, there will be no ECG response. In almost all pacemakers, the removal of the magnet causes the device to revert to pacing at the normal preprogrammed rate with the exception of Sorin pacemakers.

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