Razi Journal of Medical Sciences

Background: One of the treatments in patients with dangerous diseases particularly heart failure, is Implantable Cardioverter Defibrillator (ICD) that is used to prevent sudden cardiac death. Regarding to the superiority of ICD rather than medical treatment, the purpose of this study is the assessment of time-dependent effective factors on the rates of entered shocks to patients with ICD.

Methods: In this paper, we studied heart patients in Ghaem Hospital of Mashhad from 2005 to the first half of 2008. For various clinical reasons, ICD has been improvised for these patients. The QRS duration was measured by a digital caliper with an accuracy of a thousandth of a millimeter before we implanted ICD. Moreover, age of patients and type of ICD for each patient were recorded. Finally, we analyzed data set by a survival semiparametric statistical model through R statistical software.

Results: For these patients, all mentioned variables had time-varying effects. Age, had an additive effect on the entered shocks by this device in all patients over time. Type of ICD has both an additive effect in the period of time and depressive effect in another period. Also QRS influences the shocks induced by ICD with gentle slope.

Conclusion: For a specified patient, based on three explanatory variables, the introduced model could be used in reinforcement of correct diagnosis in installation of ICD. The single chamber type of ICD, entered less inappropriate shocks to the heart of patients than the two  other types of ICD i.e CRTD and two chamber.