Clinical trial results support the hypothesis that implantable hemodynamic monitoring (IHM) systems may reduce hospitalizations among patients with chronic heart failure (HF). The Reducing Decompensation Events Utilizing Intracardiac Pressures in Patients With Chronic Heart Failure (REDUCE hf) study was a prospective, randomized, multicenter, single-blinded trial that enrolled patients with New York Heart Association class II or III symptoms, an indication for an implantable cardioverter-defibrillator (ICD), and a previous HF hospitalization. A combination IHM-ICD was implanted and patients were randomly assigned to a treatment group in which hemodynamic information was used or a control group in which hemodynamic information was not available. Patients were followed for 12months to evaluate the primary efficacy end point of HF hospitalizations, emergency department visits, or urgent clinic visits. The trial was designed to enroll 1300 patients, but stopped at 400 patients because of IHM lead failures experienced from previous trials. A total of 202 treatment patients and 198 controls were randomized for 12-month follow-up. The primary safety end point was met, but the rate of HF equivalents was not different between groups. REDUCE hf was unable to test clinical efficacy end points adequately. The device combining IHM-ICD technology was safe and functioned appropriately. Patients at high risk for decompensated HF have high baseline filling pressures and demonstrate consistent increases as the process of congestion worsens to the time of hospitalization. © 2011 Wiley Periodicals, Inc.