title: Stratifying patients at the risk of heart failure hospitalization using existing device diagnostic thresholds.
abstract: BACKGROUND
  Heart failure hospitalizations (HFHs) cost the US health care system ∼$20 billion annually. Identifying patients at risk of HFH to enable timely intervention and prevent expensive hospitalization remains a challenge. Implantable cardioverter defibrillators (ICDs) and cardiac resynchronization devices with defibrillation capability (CRT-Ds) collect a host of diagnostic parameters that change with HF status and collectively have the potential to signal an increasing risk of HFH. These device-collected diagnostic parameters include activity, day and night heart rate, atrial tachycardia/atrial fibrillation (AT/AF) burden, mean rate during AT/AF, percent CRT pacing, number of shocks, and intrathoracic impedance. There are thresholds for these parameters that when crossed trigger a notification, referred to as device observation, which gets noted on the device report. We investigated if these existing device observations can stratify patients at varying risk of HFH.
  
  
  METHODS
  We analyzed data from 775 patients (age: 69 ± 11 year, 68% male) with CRT-D devices followed for 13 ± 5 months with adjudicated HFHs. HFH rate was computed for increasing number of device observations. Data were analyzed by both excluding and including intrathoracic impedance. HFH risk was assessed at the time of a device interrogation session, and all the data between previous and current follow-up sessions were used to determine the HFH risk for the next 30 days.
  
  
  RESULTS
  2276 follow-up sessions in 775 patients were evaluated with 42 HFHs in 37 patients. Percentage of evaluations that were followed by an HFH within the next 30 days increased with increasing number of device observations. Patients with 3 or more device observations were at 42× HFH risk compared to patients with no device observation. Even after excluding intrathoracic impedance, the remaining device parameters effectively stratified patients at HFH risk.
  
  
  CONCLUSIONS
  Available device observations could provide an effective method to stratify patients at varying risk of heart failure hospitalization.
authors.affiliation: Medtronic Inc., Minneapolis, MN, USA. Electronic address: vinod.sharma@medtronic.com.
authors.forename: Vinod
authors.initials: V
authors.lastname: Sharma
authors.affiliation: Lancaster General Hospital, Lancaster, PA, USA.
authors.forename: Lisa D
authors.initials: LD
authors.lastname: Rathman
authors.affiliation: Lancaster General Hospital, Lancaster, PA, USA.
authors.forename: Roy S
authors.initials: RS
authors.lastname: Small
authors.affiliation: Sidney Kimmel Medical College, Philadelphia, PA, USA.
authors.forename: David J
authors.initials: DJ
authors.lastname: Whellan
authors.affiliation: Medtronic Inc., Minneapolis, MN, USA.
authors.forename: Jodi
authors.initials: J
authors.lastname: Koehler
authors.affiliation: Medtronic Inc., Minneapolis, MN, USA.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Warman
authors.affiliation: Ohio State University Heart and Vascular Center, Columbus, OH, USA.
authors.forename: William T
authors.initials: WT
authors.lastname: Abraham
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001281:Atrial Fibrillation / Q000175:diagnosis*; D017147:Defibrillators, Implantable; D004554:Electric Countershock / Q000379:methods; D005260:Female; D006333:Heart Failure / Q000175:diagnosis*; D006339:Heart Rate / Q000502:physiology; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012306:Risk
keywords: Ambulatory monitoring; Heart failure; Heart failure hospitalization; Implantable device diagnostics; Intrathoracic impedance