Changes in Cardiac Indices from Implanted Defibrillator-Stored Electrograms Due to Acquisition and Preprocessing Conditions

A wide number of cardiac indices have been proposed to describe electrocardiograms (ECG) during Ventricu-lar Fibrillation (VF), and they can be useful when analy-zing electrograms (EGM) stored in Implantable Cardio-verter Defibrillator (ICD) during spontaneous VF. Howe-ver, the dependence of their measurement on acquisition and preprocessing conditions has not been so far statisti-cally quantified. We propose a systematic procedure based on nonparametric bootstrap resampling methods to obtain standard errors and confidence intervals for a test. This test detects changes in the statistical distribution of car-diac indices from ICD-stored EGM during VF, due to dis-crepancies in acquisition and preprocessing conditions. As an application example, significant changes in the distribu-tions of selected spectral indices due to lead configuration were found by comparing measurements obtained from si-multaneously recorded unipolar and bipolar EGM during VF. Our nonparametric bootstrap approach can be readily applied to the measurement of cardiac indices, allowing us to study their changes under a diversity of conditions in a systematic way. 1