Pacemaker failure induced by radiotherapy.

It is well documented that radiation therapy can have significant transitory and permanent effects on the function of cardiac pacemakers. In this study 18 multiprogrammable pacemakers were tested to establish any pattern by which these pacemakers are affected. The results confirm previous predictions on how pacemakers are damaged. The damage could be divided essentially into three types: (1) temporary change to interference or safety mode pacing lasting for the duration of the irradiation only; (2) change to interference mode pacing--from which recovery may occur after reprogramming the pacemaker; and (3) severe damage; in this case the pacemaker stops generating pulses. Recovery from this may occur a long time after the end of the treatment, but this recovery is mostly incomplete and the pacemaker cannot be used reliably thereafter. Therefore it is essential that patients with implanted pacemakers undergoing radiation therapy, should be monitored closely during the course of the treatment and for a few weeks thereafter.