Implantable cardioverter defibrillator (ICD) devices with or without cardiac resynchronization therapy (CRT-D) have the ability to continuously monitor heart rate variability, daily heart rate, and patient activity. Changes in these measures have been associated with heart failure prognosis. In addition, ICD or CRT-D devices also have the ability to measure daily intrathoracic impedance. Previous data have demonstrated that device-based intrathoracic impedance measurements correlate with pulmonary capillary wedge pressure and fluid retention, both of which are common measures of heart failure status. The objective of this study is to evaluate whether the heart rate variability, daily heart rate, and/or intrathoracic impedance can be used in conjunction with other methods to determine if patients are ready for hospital discharge. This will be the first step in potentially developing an inpatient care strategy which includes implantable device data. It is hypothesized that device diagnostic data will identify an appropriate and safe time to discharge patients admitted for worsening heart failure symptoms before usual clinical indicators. More specifically, we hypothesize that device data will "normalize" at least one day prior to the clinical indicators of readiness for discharge and patients discharged prior to "normalization" of the device data will be at greater risk for rehospitalization
