title: Utility of intrathoracic impedance monitoring in pediatric and congenital heart disease.
abstract: BACKGROUND
  The utility of cardiac device-based intrathoracic monitoring (OptiVol, Medtronic Inc., Minneapolis, MN, USA) for congestive heart failure (CHF) exacerbation has not been evaluated in pediatric or congenital heart disease patients.
  
  
  METHODS
  This was a retrospective study of all patients at a single center with an endocardial OptiVol capable device. OptiVol index values were collected in 2-week bins from January 2007 to December 2010. The clinical outcomes were CHF exacerbation defined as hospitalization or medication change for CHF and device-treated ventricular arrhythmia based on remote or in-office device interrogation. Clinical and OptiVol data were collected by separate investigators blinded to the other parameter. OptiVol data were correlated to the clinical outcomes to determine sensitivity and predictability for multiple threshold values in the entire cohort and pediatric and congenital subgroups.
  
  
  RESULTS
  Forty-seven patients were included. A total of 1,106 months of OptiVol data were collected. Median age of the cohort was 18 years (range 6-58 years). There were 23 pediatric, median age 13 years (range 6-16), at device implant, and 18 patients, median age 31 years (range 13-58), considered at risk for heart failure at implant. There were three heart failure exacerbations and 17 treated ventricular arrhythmias. The study population-specific positive predictive value (PPV) of OptiVol was low (sensitivity 33% and PPV ≤4.4%) for both CHF exacerbation and arrhythmias in all analyzed groups.
  
  
  CONCLUSIONS
  The sensitivity and positive predictive value of intrathoracic impedance monitoring was low in this population of adult congenital and pediatric patients. Recent improvements to the OptiVol algorithm may decrease these deficiencies.
authors.affiliation: Department of Pediatrics and Communicable Diseases, Division of Pediatric Cardiology, University of Michigan, Ann Arbor, Michigan 48109, USA. mlapage@med.umich.edu
authors.forename: Martin J
authors.initials: MJ
authors.lastname: LaPage
authors.forename: Johannes
authors.initials: J
authors.lastname: von Alvensleben
authors.forename: Macdonald
authors.initials: M
authors.lastname: Dick
authors.forename: Gerald
authors.initials: G
authors.lastname: Serwer
authors.forename: David J
authors.initials: DJ
authors.lastname: Bradley
mesh_terms: D000293:Adolescent; D000328:Adult; D002307:Cardiography, Impedance / Q000706:statistics & numerical data*; D002648:Child; D005260:Female; D006330:Heart Defects, Congenital / Q000175:diagnosis* / Q000453:epidemiology / Q000628:therapy*; D006333:Heart Failure / Q000175:diagnosis* / Q000453:epidemiology / Q000517:prevention & control*; D006801:Humans; D008297:Male; D008824:Michigan / Q000453:epidemiology; D008875:Middle Aged; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D055815:Young Adult
keywords: congestive heart failure; defibrillation - ICD; electrophysiology - clinical