Design dependent loss of telemetry: uplink telemetry hold.
Bidirectional telemetry in cardiac pacing is the ability of the programmer to communicate with the pacemaker and vice versa. It is an essential capability if one is to interrogate the pacemaker as to its programmed parameters and to access the diagnostic capabilities incorporated in the present generation pacemakers. Pacemaker to programmer telemetry capability was lost in two Medtronic SymbiosR pacemakers due to a design eccentricity termed "uplink telemetry hold". It is initiated by a complex sequence of spontaneous sensed and internal timing events, once activated it cannot be reversed in the clinical setting. It is potentially dangerous in that the subsequent application of a magnet over the pacemaker can result in total output inhibition. The initiating sequence of events included activation of the "cancel magnet" command. If that command is not activated, "uplink telemetry hold" cannot occur. Once telemetry uplink hold does occur, the pulse generator should be replaced.