Analysis of intracardiac electrogram changes

The main purpose of this study is to investigate if sinus conducted beats in patients with a conventional ICD have changing intracardiac electrograms (EGM) and if any association with ventricular tachycardia or ventricular fibrillation (VT/VF) exists. Thirty-two patients with ICD implants were included. Sinus conducted EGM complexes were investigated. For each beat similarity measures were calculated in relation to all other beats. All beats satisfying the beat similarity criterion were allocated to the same morphology group. Normal beats were defined according to the beat morphology group similarity between visits. If the similarity between these normal beat clusters did not satisfy the similarity criterion, this was defined as EGM change. The number of EGM morphology groups were also observed. During the observation period EGM changed in 7 (20%) of the patients while 14 (44%) had >; 5 EGM morphology groups. No association with VT/VF was observed, but the number of morphology groups increased significantly by age.