This clinical investigation is a prospective, non-randomized, multi-center, pivotal trial.This trial is being performed in order to demonstrate the sensivity of the diagnostic feature "Physiological Diagnostic" (PhD).

The purpose of this study is to evaluate the performance of a new sensor-based diagnostic feature, physiological Diagnostic (PhD)which as been implemented in the PARADYM CRT Cardiac Resynchronization System with defibrillation capabalities (PARADYM CRT System,model 8770.

Inclusion Criteria:

• Patient eligible for implantation of a CRT-D device according to current available guidelines for cardiac resynchronization therapy
• Severe HF (NYHA Class III or IV) at the time of enrollment
• At least one HF-related event (as defined for primary objective) within the last 6 months before enrolment
• Subject continues to have heart failure symptoms despite receiving optimal medical therapy consistent with current practice guidelines for the pharmacological management of heart failure
• Scheduled for implant of a PARADYM 8770
• Signed and dated informed consent

Exclusion Criteria:

• Any contraindication for standard cardiac pacing
• Any contraindication for ICD therapy
• Abdominal implantation side
• Hypertrophic or obstructive cardiomyopathy
• Acute myocarditis
• Unstable coronary symptoms (unstable angina or myocardial infarction) within the last month
• Recent (within the last month) or planned cardiac revascularization or coronary angioplasty
• Correctable valvular disease that is the primary cause of heart failure
• Mechanical tricuspid valve
• Receiving continuous intra-venous infusion of positive inotropic therapy or intermittent therapy (intra-venous infusion) more than twice per week
• Heart transplant recipient
• Renal insufficiency requiring dialysis
• Already included in another clinical study
• Life expectancy less than 12 months
• Inability to understand the purpose of the study or refusal to cooperate
• Inability or refusal to provide informed consent and, if not part of the informed consent, a Health Insurance Portability and Accountability Act (HIPAA) authorization
• Unavailability for scheduled follow-up at the implanting center
• Known sensitivity to 1 mg dexamethasone sodium phosphate (DSP)
• Under guardianship
• Age of less than 18 years
• Pregnancy (Women of childbearing potential should have a negative pregnancy test prior to enrollment)