INAPPROPRIATE PAUSES DURING BRADYCARDIA PACING IN A 3RD-GENERATION IMPLANTABLE CARDIOVERTER-DEFIBRILLATOR

Many ICD devices have the capability for back up bradycardia pacing. B ecause of the use of a single sensing algorithm for both bradycardic a nd tachycardia functions, they may be prone to certain ''sensing error s.'' Following implantation of an ICD in a patient with long QT syndro me, ''inappropriate'' pauses were noted during bradycardia pacing, whi ch were exactly twice the programmed pacing cycle length. This was due to an automatic increase in the device's sensitivity during pacing, a characteristic of the automatic gain control of this particular ICD. Proper recognition of this ICD's special features, known as ''lower th reshold crossing,'' allowed noninvasive rectification of the problem a nd prevented these pauses.