CCM in Heart Failure With Preserved Ejection Fraction

1. Inclusion criteria 1. Baseline ejection fraction ≥ 50% (as assessed by echocardiogram within 30 days of enrollment and confirmed by the echo core laboratory). 2. NYHA class II or III symptoms despite receiving stable optimal medical therapy (OMT) for at least 30 days based on patient's medical records (chronic stable, not transient or crescendo heart failure or angina pectoris) 3. Stable optimal medical therapy for Heart failure for 3 months. 4. NT-proBNP \> 220 pg/ml for subjects in sinus rhythm or \> 600 pg/ml for subjects in atrial fibrillation 5. Has the following (as assessed by the core lab): * LAVi ≥ 34 ml/m² or LVH \>12mm AND either * E/e' ≥ 13 OR * septal e' \< 7 cm/s or lateral e' \<10 cm/s 6. Patient giving informed consent, willing to be available for scheduled study follow-up visits, and able to complete all testing of the study protocol 2. Exclusion criteria 1. Age below 40 or greater than 80 2. Patients with expected lifespan of less than 12 months from time of enrollment 3. Subjects referred to an institution based on a judicial or administrative order 4. Dilated left ventricle, as evidenced by LVEDVI \>= 97 mL/m2 (as assessed by the echo core lab) 5. Primary cardiac valvular disease (anything more than grade 2) 6. Congenital or untreated ischemic heart disease 7. Infiltrative / inflammatory / genetic cardiomyopathy as documented in the medical record (e.g. amyloid, hemochromatosis, myocarditis, hypertrophic cardiomyopathy, M. Fabry, cardiac tumor), or persistent large pericardial effusion 8. Unstable or frequent (\>1 episode/week) angina pectoris 9. Hospitalization for HF requiring the use of inotropic support or IABP within 30 days of enrollment 10. Systolic Blood Pressure \> 160 mmHg 11. Uncorrected severe anemia (e.g. hemoglobin \<9g/dL) 12. PR interval greater than 375 ms 13. Exercise tolerance limited due to noncardiac disorders (e.g. deconditioning, severe lung disease, frailty) 14. Scheduled for a cardiac surgery or a PCI procedure, or had a cardiac surgery procedure within 90 days or a PCI procedure within 30 days prior to enrollment 15. Myocardial infarction within 90 days of enrollment 16. Cardioversion within 30 days of enrollment 17. History of significant ectopy either on 12-lead ECG or Holter monitoring (more than 10% PVCs). 18. Heart rate \> 110 bpm on ECG for patients with atrial fibrillation 19. Mechanical tricuspid valve 20. Prior heart transplant or ventricular assist device 21. Pregnant or planning to become pregnant during the study 22. Breastfeeding subjects 23. Subject participating in another medical therapy or device related study, unrelated to CCM™, at the same time or within 30 days prior to enrollment into this study 24. Subjects on dialysis, or with documented GFR\<30 or with other major medical disorder (e.g. severe anemia, liver failure) 25. Subjects with any active non-cardiac implants