Larger change in intra-thoracic impedance before and during heart failure hospitalization is associated with longer length of stay in patients with cardiovascular implanted electronic devices

Abstract

Abstract Background Intra-thoracic impedance measured in implantable cardioverter defibrillators (ICD) and cardiac resynchronization therapy defibrillators (CRTD) is a measure of intravascular blood volume and have been shown to correlate with intracardiac pressures in previous studies. Purpose We investigated whether amount of change of intrathoracic impedance before admission is associated with length of stay (LOS) during heart failure (HF) hospitalizations in a large real-world cohort of patients with ICD/CRTD devices. Methods We linked a deidentified database of aggregated electronic health record during the period from 2007-2017 to a manufacturer’s device data warehouse with device based continuous diagnostic monitoring data. Patients with ICD/CRTD implants with intra-thoracic impedance measurements were included for this study. HF event was defined as an inpatient, emergency department, or observation unit stay in a hospital with primary diagnosis of HF and intravenous diuretics administration. Relative change of daily intra-thoracic impedance measurement from 60 days prior to admission and date of admission as well as from admission to discharge were compared in HF events with LOS < 5 days and LOS ≥ 5 days using a Wilcoxon rank sum test. Results A total of 17,886 patients with 1.8±1.2 years of follow-up met inclusion criteria. The average age of patients was 66.6 ±12.3 years, with 72% being males, and 51% with ICD devices. The relative change in intra-thoracic impedance from 60 days prior till date of admission and from admission to discharge for HF events with LOS < 5 days and LOS ≥ 5 days are shown in Table. A total of 1456 patients had 1720 HF events of which 874 events had LOS< 5 days and 846 had LOS≥ 5 days. HF events with a longer length of stay (LOS ≥ 5 days) had a higher relative decrease in intra-thoracic impedance prior to admission compared to HF events with a shorter length of stay. HF events with a longer length of stay (LOS≥ 5 days) had a higher relative increase in intra-thoracic impedance during hospital stay. Conclusions In a large real-world population of patients with ICD/CRTD devices, longer length of stay is more likely in patients with a larger relative decrease in intra-thoracic impedance prior to admission, indicating more accumulated fluid. Further, larger relative increase in intra-thoracic impedance during hospital stay was observed in patients with longer length of stay, indicating more fluid removal.