Single event upsets in implantable cardioverter defibrillators

Single event upsets (SEU) have been observed in implantable cardiac defibrillators. The incidence of SEUs is well modeled by upset rate calculations attributable to the secondary cosmic ray neutron flux. The effect of recent interpretations of the shape of the heavy ion cross-section curve on neutron burst generation rate calculations is discussed. The model correlates well with clinical experience and is consistent with the expected geographical variation of the secondary cosmic ray neutron flux. The observed SER was 9.3 x 10(-12) upsets/bit-hr from 22 upsets collected over a total of 284672 device days. This is the first clinical data set obtained indicating the effects of cosmic radiation on implantable devices. Importantly, it may be used to predict the susceptibility of future implantable device designs to cosmic radiation. The significance of cosmic radiation effects relative to other radiation sources applicable to implantable devices is discussed.