title: Intrathoracic impedance monitoring to detect chronic heart failure deterioration: relationship to changes in NT-proBNP.
abstract: BACKGROUND
  An alert algorithm, based on intrathoracic impedance monitoring, has been incorporated into a cardiac resynchronisation device (CRT) to detect pulmonary fluid accumulation, and to audibly alert patients to decompensating chronic heart failure (CHF).
  
  
  OBJECTIVE
  To evaluate this algorithm, alert events were correlated with changes in NT-proBNP concentration and CHF status.
  
  
  RESULTS
  In a prospective observational study of 62 patients (89% male, aged 67+/-1 year), NT-proBNP plasma concentrations, clinical CHF status, and device data were collected at enrolment, during regular follow-up and at device alerts. Over a mean follow-up of 27+/-2 weeks, pooled data indicated a weak, but significant inverse relationship between relative changes in intrathoracic impedance and NT-proBNP (r=-0.3; p<0.001). In 52 device alerts from 35 patients, NT-proBNP increased by 66+/-19% from 2039+/-331 pg/ml (p<0.001). The increase in NT-proBNP was higher in alerts with clinical signs of CHF deterioration (n=30, 89+/-25%; p<0.001) than in alert events without clinical signs (n=22, 25+/-15%; p=n.s.).
  
  
  CONCLUSIONS
  Intrathoracic impedance based alert events are associated with a significant increase in NT-proBNP concentration. These data indicate that intrathoracic impedance monitoring might facilitate the outpatient management of CHF patients with implanted CRT devices.
authors.affiliation: Herzzentrum Göttingen, Abteilung Kardiologie und Pneumologie, Georg-August-Universität Göttingen, Robert-Koch-Str. 40, 37075 Göttingen, Germany. larsluethje@med.uni-goettingen.de <larsluethje@med.uni-goettingen.de>
authors.forename: Lars
authors.initials: L
authors.lastname: Lüthje
authors.forename: Dirk
authors.initials: D
authors.lastname: Vollmann
authors.forename: Till
authors.initials: T
authors.lastname: Drescher
authors.forename: Peter
authors.initials: P
authors.lastname: Schott
authors.forename: Dieter
authors.initials: D
authors.lastname: Zenker
authors.forename: Gerd
authors.initials: G
authors.lastname: Hasenfuss
authors.forename: Christina
authors.initials: C
authors.lastname: Unterberg
mesh_terms: D000368:Aged; D000465:Algorithms; D002307:Cardiography, Impedance / Q000295:instrumentation*; D002908:Chronic Disease; D017147:Defibrillators, Implantable; D018450:Disease Progression; D004867:Equipment Design; D005260:Female; D006333:Heart Failure / Q000097:blood / Q000175:diagnosis*; D006801:Humans; D008297:Male; D018670:Monitoring, Ambulatory / Q000295:instrumentation*; D008991:Monitoring, Physiologic; D020097:Natriuretic Peptide, Brain / Q000097:blood*; D010446:Peptide Fragments / Q000097:blood*; D012984:Software
chemical_list: D010446:Peptide Fragments; C109794:pro-brain natriuretic peptide (1-76); D020097:Natriuretic Peptide, Brain