title: Physiopathologic correlates of intrathoracic impedance in chronic heart failure patients.
abstract: BACKGROUND
  Increased plasma levels of amino-terminal fraction of brain natriuretic peptide (NT-proBNP) and alterations of diastolic filling as described by Doppler transmitral flow pattern are well-known markers of decompensated heart failure (HF). Recently, some implantable defibrillators have allowed monitoring of intrathoracic impedance, which is related to lung water content, potentially indicating HF deterioration. The aim of this study was to assess the correlation between intrathoracic impedance and NT-proBNP and echo-Doppler transmitral flow indexes.
  
  
  METHODS
  Data were collected from 111 HF patients, in six Italian centers. All patients were on optimal medical therapy. Device diagnostics, echographic data, NT-proBNP determination, and clinical status as assessed by the Heart Failure Score (HFS) were registered at baseline, at bimonthly visits, and at unscheduled examinations due to HF decompensation or device alerts.
  
  
  RESULTS
  Over a median follow-up of 413 days, 955 examinations were performed. Intrathoracic impedance was significantly correlated with NT-proBNP (P = 0.013) and with mitral E-wave deceleration time (DtE) (P = 0.017), but not with HFS. At the time of confirmed alert events, NT-proBNP was significantly higher than during confirmed nonalert event examinations; DtE did not differ, whereas impedance was significantly lower.
  
  
  CONCLUSIONS
  A decrease in intrathoracic impedance is inversely correlated with NT-proBNP and directly correlated with DtE. Intrathoracic impedance monitoring therefore has the physiologic basis for being a useful tool to identify early HF decompensation.
authors.affiliation: Divisione Clinicizzata di Cardiologia, Azienda Ospedaliera Istituti Ospitalieri di Verona, Verona, Italy. lucatomasi1@gmail.com
authors.forename: Luca
authors.initials: L
authors.lastname: Tomasi
authors.forename: Gabriele
authors.initials: G
authors.lastname: Zanotto
authors.forename: Luisa
authors.initials: L
authors.lastname: Zanolla
authors.forename: Giorgio
authors.initials: G
authors.lastname: Golia
authors.forename: Renato
authors.initials: R
authors.lastname: Ometto
authors.forename: Carlo
authors.initials: C
authors.lastname: Bonanno
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Vergara
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Maines
authors.forename: Gabriele
authors.initials: G
authors.lastname: Lonardi
authors.forename: Emanuela
authors.initials: E
authors.lastname: Visentin
authors.forename: Werner
authors.initials: W
authors.lastname: Rauhe
authors.forename: Loredana
authors.initials: L
authors.lastname: Latina
authors.forename: Cosimo
authors.initials: C
authors.lastname: Perrone
authors.forename: Annamaria
authors.initials: A
authors.lastname: Varbaro
authors.forename: Tiziana
authors.initials: T
authors.lastname: DE Santo
mesh_terms: D000368:Aged; D015415:Biomarkers / Q000097:blood; D002307:Cardiography, Impedance / Q000379:methods; D002908:Chronic Disease; D003326:Coronary Circulation; D017097:Electric Impedance; D005260:Female; D006333:Heart Failure / Q000175:diagnosis* / Q000503:physiopathology*; D006801:Humans; D007558:Italy; D008297:Male; D020097:Natriuretic Peptide, Brain / Q000097:blood*; D010446:Peptide Fragments / Q000097:blood*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013223:Statistics as Topic; D013318:Stroke Volume
chemical_list: D015415:Biomarkers; D010446:Peptide Fragments; C109794:pro-brain natriuretic peptide (1-76); D020097:Natriuretic Peptide, Brain