The goal of this clinical trial is to demonstrate that the OPTIMIZER® Integra CCM-D System (the "CCM-D System") can safely and effective convert induced ventricular fibrillation (VF) and spontaneous ventricular tachycardia and/or ventricular fibrillation (VT/VF) episodes in subjects with Stage C or D heart failure who remain symptomatic despite being on guideline-directed medical therapy (GDMT), are not indicated for cardiac resynchronization therapy (CRT), and have heart failure with reduced left ventricular ejection fraction (LVEF ≤40%).

Eligible subjects will be implanted with the CCM-D System. A subset of subjects will be induced into ventricular fibrillation "on the table" in the implant procedure room. During the follow-up period, inappropriate shock rate and device-related complications will be evaluated. The follow-up period is expected to last at least two years.

Inclusion Criteria:

Individuals must meet all the following:

1. Patient is aged 18 years or older;
2. Patient meets the Stage C or D criteria of the Universal Definition of Heart Failure ;
3. Patient has HFrEF (LVEF ≤40%);
4. Patient is on GDMT for heart failure;
5. Patient has a Class I or Class II indication for an ICD
6. Patient has a reasonable expectation of meaningful survival of > 1 year;
7. Patient has either non-ischemic cardiomyopathy or ischemic cardiomyopathy and is at least 40 days post-MI, if an MI occurred;
8. Patient is willing to give informed consent, available for scheduled study follow-up visits, and able to complete all testing described in the study protocol at the investigational site location.

Exclusion Criteria:

An individual who meets any of the following criteria will be excluded from participation in this study:

1. Patients should not have severe AI or AS, and should not have MS; additionally, patients undergoing DE testing should not have severe MR;
2. Patients who have undergone mitral valve repair or clip within 90 days prior to study consent;
3. Cardiac surgery within 90 days or a PCI procedure within 30 days prior to study consent;
4. Prior heart transplant or ventricular assist device;
5. Implanted mechanical tricuspid valve;
6. PR interval greater than 375ms or advanced AV block;
7. In situ S-ICD, pacemaker, or CRT device;
8. Indicated for CRT;
9. End stage renal disease, currently on dialysis, or with other major medical disorder (e.g. liver failure, terminal cancer);
10. Indicated for permanent bradyarrhythmia pacing;
11. Unstable angina pectoris within 30 days prior to study consent;
12. Pregnant or planning to become pregnant during the study;
13. Participating in another cardiac investigational device or drug study at the same time (or within 30 days prior to study consent); Note: Registries and other observational studies are acceptable.
14. Other criteria that preclude Optimizer INTEGRA CCM-D implantation and/or CCM therapy, as determined by Investigator.