The SENSE-HF study is a prospective, observational, international multi-center study prospectively evaluating the sensitivity and positive predictive value of the OptiVol Fluid Trends data in predicting Heart Failure related hospitalizations and health care utilizations associated with signs and/or symptoms of pulmonary congestion, and to define OptiVol clinical guidelines for subject therapy management.

The SENSE-HF study prospectively evaluates the OptiVol feature in the prediction of Heart Failure related events associated with signs and symptoms of pulmonary congestion and in the subject HF therapy management.

The OptiVol feature is based on the measurement of daily intrathoracic impedance values, measurements that can be used to track changes in the subject's thoracic fluid status over time. An Alert warns the patient whenever a programmable threshold has been reached.

The study is divided into three phases.

The first phase is double-blinded and designed to determine the sensitivity and positive predictive value of the OptiVol Fluid Trends data for the detection of Heart Failure related hospitalizations with signs and/or symptoms of pulmonary congestion.

In the second phase of the study, the Alert is turned ON and the positive predictive value of the first OptiVol Patient Alert for the development of signs and/or symptoms of pulmonary congestion will be evaluated.

The third phase of the study allows for remote subject therapy management using the OptiVol Patient Alert. The patient management strategy is then based on the experience gained in the second study phase Physician actions taken in the occurrence of a Patient Alert will be summarized.

Inclusion Criteria:

• Successfully implanted InSync Sentry device (< 34 days post implant or pocket revision)in the pectoral region;
• At least one HF-related hospitalization that required administration of IV medication (inotropes, nitrates, diuretics) within the last 12 months
• The Subject has a market released, transvenous, high voltage Right Ventricular lead
• The Subject is able to detect a Patient Alert signal

Exclusion Criteria:

• <18 years of age (or under a minimum age required by local law)
• Moderate to severe Chronic Obstructive Pulmonary Disease (COPD)
• Post heart transplant or awaiting heart transplantation
• Primary pulmonary hypertension
• Renal insufficiency requiring dialysis

Amendment to the inclusion criteria (Jul 06):

• Inclusion of patients with Concerto/Virtuoso devices.
• At least one HF-related hospitalization that required administration of IV (or uptitration of the oral medication)(inotropes, nitrates, diuretics)within the last 12 months