Prediction of All-Cause Mortality Based on the Direct Measurement of Intrathoracic Impedance.
Circ Heart Fail. 2016 Jan;9(1):e002543
Authors: Zile MR, Sharma V, Johnson JW, Warman EN, Baicu CF, Bennett TD
BACKGROUND: Intrathoracic impedance-derived OptiVol fluid index calculated using implanted devices has been shown to predict mortality; direct measurements of impedance have not been examined. We hypothesized that baseline measured impedance predicts all-cause mortality; changes in measured impedance result in a change in the predicted mortality; and the prognostic value of measured impedance is additive to the calculated OptiVol fluid index.
METHODS AND RESULTS: A retrospective analysis of 146 238 patients within the Medtronic CareLink database with implanted devices was performed. Baseline measured impedance was determined using daily values averaged from month 6 to 9 after implant and were used to divide patients into tertiles: group L=low impedance, ≤65 ohms; group M=medium impedance, 66 to 72 ohms; group H=high impedance, ≥73 ohms. Change in measured impedance was determined from values averaged from month 9 to 12 post implant compared with the 6- to 9-month values. OptiVol fluid index was calculated using published methods. All-cause mortality was assessed beginning 9 months post implant; changes in mortality was assessed beginning 12 months post implant. Baseline measured impedance predicted all-cause mortality; 5-year mortality for group L was 41%, M was 29%, and H was 25%, P<0.001 among all groups. Changes in measured impedance resulted in a change in the predicted mortality; the prognostic value of measured impedance was additive to the OptiVol fluid index.
CONCLUSIONS: Direct measurements of intrathoracic impedance using an implanted device can be used to stratify patients at varying mortality risk.
PMID: 26699393 [PubMed - in process]