12 lead ECG

• right atrial pacing (small pacing stimuli visible in DII, DIII) and spontaneous ventricular activation
• magnet application
• asynchronous atrio-ventricular pacing (DOO mode, 85 bpm)
• magnet removal and return to right atrial pacing/ventricular sensing

Comments

• magnet application remains widely used in clinical practice to assess pacemaker function and battery depletion in the absence of a programmer
• when a magnet is applied over a pacemaker, the special reed-switch is closed within the pulse generator resulting in asynchronous pacing at the magnet rate
• in patients with intrinsic rhythm inhibiting pacing, magnet application converts the device to asynchronous pacing and may confirm the ability or inability to capture
• change in magnet rate can reveal elective replacement indicator determining the need for replacement
• magnet application can be used therapeutically to interrupt an episode of pacemaker-mediated tachycardia
• magnet application can also restore pacing and prevent inhibition and asystole in pacemaker-dependent patients with oversensing
• details of the magnet mode and magnet rate vary among the different manufacturers
• in some devices, magnet application may trigger automatic threshold search or electrogram storage rather than asynchronous pacing; the patient may freeze and store electrograms with external magnet application during symptomatic events
• in some devices, the magnet mode can be programmed off resulting in the absence of modification of pacing rate after magnet application