Biomagnetic risk stratification by QRS fragmentation in patients with implanted cardioverter defibrillators

Abstract

Implantation rate of Implantable Cardioverter Defibrillators (ICDs) has been rising to 20 per million population. The mean age is increasing and the costs for one additional year of life in chronic heart failure ranges from US34,000 in older trials up to US50,000 (CABG Patch, DINAMIT). Further research is needed on the risk stratification of patients in whom ICDs are most likely to be clinically and cost-effective. Prospective studies are ongoing for validating the use of QRS-fragmentation [1] as predictor of arrhythmic events. Unfortunately, this kind of studies needs time. A faster way is to do retrospective studies on patients with already implanted ICDs. Until now, it has not been possible to perform biomagnetic measurements of QRS-fragmentation in patients with ICDs. In fact, the presence of this device in the thorax (normally it is located on the left shoulder) of the patient leads to very strong interferences in biomagnetic measurements due to the ferromagnetic case of the batteries. These interferences are order of magnitude larger than the biomagnetic signal of the heart. For this reason, ICDs or pacemakers are among the exclusion criteria for studies concerning magnetic field imaging (MFI). With a post-processing method based on Blind Source Separation, we were able to extract cardiac signals from biomagnetic signals that are disturbed by an ICD. Thus offers the possibility for a QRS fragmentation analysis in patients with already implanted ICDs. © 2009 Springer Berlin Heidelberg.