The study is intended to demonstrate the safe implant of small receiver-electrodes into the endocardial surface of the left ventricle and to demonstrate its utility in providing cardiac resynchronization therapy in heart failure patients.

Eligible patients will undergo an acoustic window assessment using transthoracic echocardiography. Patients with adequate acoustic windows will undergo implantation of the WiCS-LV system.

Patients will undergo evaluations pre-hospital discharge, and at one month, 3 months, and 6 months post implantation. Extended follow-up will be obtained via a registry at 1, 2, 3, 4, and 5 years post implantation.

Inclusion Criteria:

Patients with standard indications for CRT based upon the most recent ESC/EHRA guidelines AND meeting criteria for one of these two categories:

1. Patients with previously implanted pacemakers or ICD's and meeting standard indications for CRT but in whom standard CRT is not advisable due to known high risk - referred to as "upgrades". Justifications for not using standard CRT must be documented in a CRF.
2. Patients in whom coronary sinus lead implantation or attempted implantation for CRT has failed to provide demonstrable therapy benefit - referred to as "untreated"

Exclusion Criteria:

1. Inability to comply with the study follow-up or other study requirements
2. History of chronic alcohol/drug abuse and currently using alcohol/drugs
3. Non-ambulatory (or unstable) NYHA class 4
4. Contraindication to heparin
5. Contraindication to both chronic anticoagulants and antiplatelet agents
6. Triple anticoagulation therapy (warfarin, clopidogrel, ASA, and other agents)
7. Thrombocytopenia (platelet count <150,000)
8. Contraindication to iodinated contrast agents
9. Intracardiac thrombus by transesophageal echocardiography
10. Age less than 18 years or greater than 75
11. Attempted IPG implant within 3 days
12. Life expectancy of less than 12 months
13. Chronic hemodialysis
14. Stage 4 or 5 renal dysfunction defined as GFR <30
15. Grade 4 mitral valve regurgitation
16. Myocardial infarction within one month
17. Major cardiac surgery within one month
18. History of a pericardial effusion in prior procedures
19. Female of childbearing potential, pregnant, or breastfeeding (a pregnancy test will be obtained where applicable)
20. Non-cardiac implanted electrical stimulation therapy devices