title: A critical link between heart failure self-care and intrathoracic impedance.
abstract: BACKGROUND
  Effective self-care is regarded as essential to the management of heart failure (HF). The influence of self-care on HF decompensation, however, is not well understood. Accordingly, we examined the relationship between self-care and fluid accumulation accompanying worsening HF as indexed by decreasing intrathoracic impedance (Z).
  
  
  METHODS
  Z data were collected from 58 HF patients with OptiVol enabled devices (Medtronic Inc, Minneapolis, Minnesota). Heart failure self-care was measured with the European Heart Failure Self-care Behaviour Scale. Regression modeling was used to describe the influence of HF self-care on the likelihood of a fluid index (FI) threshold crossing, the number of threshold crossings, and number of days spent above threshold.
  
  
  RESULTS
  Patients were elderly (74.98 [SD, 8.12] years), with a mean left ventricular ejection fraction of 26.21% (SD, 9.77%), and 63.7% had class New York Heart Association III HF. Patients were followed up for 317 (SD, 96) days; 65.5% had FI threshold crossings (mean 1.45 [SD, 1.56] crossings), spending an average of 33.8 (SD, 42.4) days above FI threshold. Controlling for age, sex, left ventricular ejection fraction, functional class, and duration of follow-up, each additional point on the European Heart Failure Self-care Behaviour Scale was associated with an increase in the odds of having had an FI threshold crossing (adjusted odds ratio, 1.201; 95% confidence interval, 1.013-1.424; P<.05) and more days spent above FI threshold (incidence rate ratio, 1.051; 95% confidence interval, 1.002-1.102; P<.05).
  
  
  CONCLUSIONS
  Intrathoracic impedance measurements obtained from implantable devices provide important information regarding the influence of self-care on fluid accumulation in patients with HF.
authors.affiliation: Heart Failure Program, Lancaster General Hospital, The Heart Group, Lancaster, PA 17603, USA. lisa.rathman@theheartgroup.com
authors.forename: Lisa D
authors.initials: LD
authors.lastname: Rathman
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Lee
authors.forename: Shantanu
authors.initials: S
authors.lastname: Sarkar
authors.forename: Roy S
authors.initials: RS
authors.lastname: Small
mesh_terms: D000368:Aged; D002307:Cardiography, Impedance; D004489:Edema, Cardiac / Q000175:diagnosis; D004567:Electrodes, Implanted; D005260:Female; D006333:Heart Failure / Q000175:diagnosis / Q000628:therapy*; D006801:Humans; D016014:Linear Models; D008297:Male; D018670:Monitoring, Ambulatory; D010349:Patient Compliance; D012189:Retrospective Studies; D012648:Self Care