Does Lung Impedance Correlate With Changes in BNP in Stable and Acutely Decompensated Heart Failure Patients?

The purpose of this study is to determine whether there is a relationship between serial B-natriuretic peptide (BNP) and implantable device measured intrathoracic impedance in symptomatic and asymptomatic heart failure patients over a 1-year period. Furthermore, this study will establish whether implantable device measured intrathoracic impedance trends with the distance walked on a six-minute hall walk (6MHW), an exercise-based acute measure that has also been associated with heart failure clinical status.