Inappropriate pacing inhibition triggered by QT prolongation due to T wave oversensing in an ICD recipient presenting with long QT syndrome.

Inappropriate inhibition of atrial pacing due to T-wave oversensing (TWOS) was observed in a patient presenting with congenital long QT syndrome, treated with an implantable cardioverter defibrillator (ICD) and beta-adrenergic blocker. Development of TWOS was associated with further QT interval prolongation in the absence of amplitude changes in the intracardiac T and R waves. Replacement of the ICD generator with a sensing filter designed to attenuate the intracardiac T wave suppressed TWOS and normalized the pacing functions.