Analysis of different device-based intrathoracic impedance vectors for detection of heart failure events (from the Detect Fluid Early from Intrathoracic Impedance Monitoring study)

Am J Cardiol. 2014 Oct 15;114(8):1249-56. doi: 10.1016/j.amjcard.2014.07.048. Epub 2014 Jul 30.


Detect Fluid Early from Intrathoracic Impedance Monitoring (DEFEAT-PE) is a prospective, multicenter study of multiple intrathoracic impedance vectors to detect pulmonary congestion (PC) events. Changes in intrathoracic impedance between the right ventricular (RV) coil and device can (RVcoil→Can) of implantable cardioverter-defibrillators (ICDs) and cardiac resynchronization therapy ICDs (CRT-Ds) are used clinically for the detection of PC events, but other impedance vectors and algorithms have not been studied prospectively. An initial 75-patient study was used to derive optimal impedance vectors to detect PC events, with 2 vector combinations selected for prospective analysis in DEFEAT-PE (ICD vectors: RVring→Can + RVcoil→Can, detection threshold 13 days; CRT-D vectors: left ventricular ring→Can + RVcoil→Can, detection threshold 14 days). Impedance changes were considered true positive if detected <30 days before an adjudicated PC event. One hundred sixty-two patients were enrolled (80 with ICDs and 82 with CRT-Ds), all with ≥1 previous PC event. One hundred forty-four patients provided study data, with 214 patient-years of follow-up and 139 PC events. Sensitivity for PC events of the prespecified algorithms was as follows: ICD: sensitivity 32.3%, false-positive rate 1.28 per patient-year; CRT-D: sensitivity 32.4%, false-positive rate 1.66 per patient-year. An alternative algorithm, ultimately approved by the US Food and Drug Administration (RVring→Can + RVcoil→Can, detection threshold 14 days), resulted in (for all patients) sensitivity of 21.6% and a false-positive rate of 0.9 per patient-year. The CRT-D thoracic impedance vector algorithm selected in the derivation study was not superior to the ICD algorithm RVring→Can + RVcoil→Can when studied prospectively. In conclusion, to achieve an acceptably low false-positive rate, the intrathoracic impedance algorithms studied in DEFEAT-PE resulted in low sensitivity for the prediction of heart failure events.

Publication types

  • Clinical Trial
  • Multicenter Study

MeSH terms

  • Aged
  • Algorithms
  • Cardiac Resynchronization Therapy
  • Cardiography, Impedance / instrumentation*
  • Electric Impedance
  • Equipment Design
  • Feasibility Studies
  • Female
  • Follow-Up Studies
  • Heart Failure / complications
  • Heart Failure / diagnosis*
  • Heart Failure / therapy
  • Heart Ventricles / physiopathology
  • Humans
  • Incidence
  • Male
  • Middle Aged
  • Prospective Studies
  • Pulmonary Edema / diagnosis*
  • Pulmonary Edema / epidemiology
  • Pulmonary Edema / etiology
  • Reproducibility of Results
  • United States / epidemiology