Objective: An elastic ventricular restraint device has been developed for patients with heart failure who remain symptomatic despite treatment with standard therapies. The safety and efficacy of this device are under clinical investigation. Six-month data for the first 51 patients treated worldwide are reported. We hypothesize that the Paracor HeartNet device (Paracor Medical, Sunnyvale, Calif), placed through a minithoracotomy in patients with severe dilated cardiomyopathy, improves clinical and functional status. Methods: Fifty-one patients with an ejection fraction of 35% or less, with a New York Heart Association class II or III, and receiving optimal medical therapy for at least 3 months, were selected at 15 sites (3 in Europe, 12 in the United States) to undergo implantation of the HeartNet device through a minithoracotomy. Patients were evaluated at baseline and at 6-month follow-up by echocardiography, the 6-minute walk test, cardiopulmonary exercise testing (partial oxygen pressure in mixed venous blood), New York Heart Association class, and (in the United States) the Minnesota Living with Heart Failure questionnaire. Results: The average age was 52 years (30-73 years), with a preponderance of men and nonischemic cause of heart failure. Implantation was accomplished in 50 of 51 patients (98%). Adverse events included 2 in-hospital deaths secondary to pulmonary complications (4%), additional pulmonary complications in 7 patients (14%), arrhythmia in 14 patients (27%), epicardial laceration in 2 patients (4%), and empyema in 1 patient (2%). Six-month data demonstrated significant improvement in the 6-minute walk test (+65.7, P = .002) and Minnesota Living with Heart Failure scores (-15.7, P = .002) and improvement in echocardiographic findings. Conclusion: The Paracor HeartNet device can be reliably implanted in patients with heart failure and marked reduction of left ventricular function. These data suggest a functional and clinical benefit, with a trend toward reverse remodeling, and support the conduct of a randomized controlled pivotal trial.