Problematik der asynchronen Schrittmacherstimulation

In cases where technical systems interfere with each other, normalization should be the consequence. If a pacemaker patient enters a strong magnetic field, the pacemaker switches to its asynchronous interference mode. The question whether asynchronous pacing is tolerable in all patients, is the subject of the following discussion. In the 1960s there was nothing but asynchronous stimulation in implantable and external pacemakers and numerous reports on fibrillation due to asynchronous pacing were published at that time. Even a few seconds are sufficient to elicit ventricular fibrillation. One of the youngest papers on fibrillation appeared in 2004 in which atrial ?undersensing“ was the cause of ventricular asynchronous pacing. That episodes of fibrillation under asynchronous pacing are nowadays rare is explained by modern electrodes with low thresholds, but fibrillation can also be caused by asynchronous pacing in tachycardial phases during which the fibrillation threshold is reduced. This can be verified by deaths of patients with bradycardia-tachycardia syndrome which occurred during magnetic resonance imaging. Even if very few reports have been published during the last 10 years, this is by no means evidence that they do not exist. It can be concluded that: 1) the risk of producing ventricular fibrillation by applying a magnet is low but still exists. From this it follows that physicians are duty bound to inform the patient of such risks. 2) Asynchronous pacing during tachycardia must be strictly avoided because of the reduced fibrillation threshold. 3) In pacemaker patients with sudden cardiac death, it should be investigated whether ventricular fibrillation was induced by asynchronous pacing.