title: Internal thoracic impedance monitoring: a novel method for the preclinical detection of acute heart failure.
abstract: BACKGROUND
  Acute heart failure (AHF) evolves through two phases. In the first phase, there is interstitial congestion with no clinical sign of edema (preclinical phase); the second, during which lung alveoli begin to fill with fluid, manifests as clinically overt alveolar edema. Treatment of AHF at its preclinical phase can alleviate its clinical impact. Presently, there is no technique that detects the interstitial phase of AHF. We used a device based on a new method of lung bioimpedance measurement. The device measures internal thoracic impedance (ITI), which nearly equals inherent lung bioimpedance. This method can detect small changes in lung fluid that occur during the interstitial stage of AHF.
  
  
  OBJECTIVE
  The objective of this study was to assess the feasibility and efficacy of the said new method in detecting preclinical AHF.
  
  
  METHODS
  Internal thoracic impedance and pertinent clinical parameters were monitored for 72 h in 403 patients hospitalized for an acute coronary syndrome without evidence of AHF at study entry.
  
  
  RESULTS
  Seventy patients developed AHF during monitoring. Internal thoracic impedance decreased in these patients by 16.4% (95% CI=-12.2% to -20.6%; P<.0001) from the baseline level at 44+/-15.1 min prior to the onset of lung rales. The other 333 patients had no clinical sign of AHF, and their ITI declined only by 4.5% (95% CI=2.5% to -11.5%; P=.3) compared with the baseline level.
  
  
  CONCLUSIONS
  The new method for ITI measurement is sufficiently sensitive in detecting AHF at its preclinical stage. An ITI decrease of more than 12% heralds the appearance of clinically overt AHF and, thus, allows earlier therapy.
authors.affiliation: Heart Institute, Hillel Yaffe Medical Center (affiliated to the Rappaport School of Medicine, The Technion, Haifa, Israel), Hadera 38100, Israel. shochat1@yahoo.com
authors.forename: Michael
authors.initials: M
authors.lastname: Shochat
authors.forename: Gideon
authors.initials: G
authors.lastname: Charach
authors.forename: Shmuel
authors.initials: S
authors.lastname: Meyler
authors.forename: Mark
authors.initials: M
authors.lastname: Kazatzker
authors.forename: Morris
authors.initials: M
authors.lastname: Mosseri
authors.forename: Aaron
authors.initials: A
authors.lastname: Frimerman
authors.forename: Paul
authors.initials: P
authors.lastname: Rabinovich
authors.forename: Avraham
authors.initials: A
authors.lastname: Shotan
authors.forename: Simcha
authors.initials: S
authors.lastname: Meisel
mesh_terms: D000208:Acute Disease; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D002307:Cardiography, Impedance / Q000295:instrumentation*; D005240:Feasibility Studies; D005260:Female; D006333:Heart Failure / Q000175:diagnosis* / Q000503:physiopathology; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged