Efficacy Study of Pacemakers to Treat Slow Heart Rate in Patients With Heart Failure

Inclusion Criteria 1. Age \>18 years and able to provide informed consent to enroll in the trial, or consent through a legal guardian or power of attorney. 2. Previous clinical diagnosis of HF with current NYHA Class II-III symptoms 3. At least one of the following: Hospitalization for decompensated HF, Acute treatment for HF with intravenous loop diuretic or hemofiltration, Chronic treatment with a loop diuretic for control of HF symptoms + left atrial enlargement on echocardiography or E/e' ratio (≥14 average, ≥15 septal ) on echocardiography, Resting PCWP \>15 mm Hg or LV end-diastolic pressure \>18 mmHg at catheterization for dyspnea and/or exercise PCWP/LV end-diastolic pressure \>25 mmHg, or Elevated NT-proBNP level (≥300 pg/ml ) 4. Left ventricular EF ≥40% within 12 months with clinical stability 5. Stable cardiac medical therapy for ≥30 days 6. Sinus rhythm 7. Chronotropic incompetence on recent (within 6 months) clinical or screening exercise test, defined as heart rate reserve (HRR) \<0.80 or \<0.62 if on beta blockers 8. Meet both screening criteria on clinically-performed cardiopulmonary exercise testing within 12 months. Exclusion Criteria 1. Inability to exercise, or non-cardiac condition that precludes exercise testing 2. Any contraindication to a pacemaker system 3. Non-cardiac condition limiting life expectancy to less than one year 4. Significant left sided structural valve disease (\>mild stenosis, \>moderate regurgitation) 5. Hypertrophic cardiomyopathy 6. Infiltrative or inflammatory myocardial disease (amyloid, sarcoid) 7. Pericardial disease 8. Non-group 2 pulmonary arterial hypertension 9. Chronic stable exertional angina 10. Acute coronary syndrome or revascularization within 60 days 11. Other clinically important causes of dyspnea 12. Atrial fibrillation 13. PR interval \>210 msec 14. Resting heart rate (HR) \> 100 bpm 15. A history of reduced ejection fraction (EF\<40%) 16. Advanced chronic kidney disease (GFR \< 20 ml/min/1.73m2 by modified MDRD equation) 17. Women of child bearing potential without negative pregnancy test and effective contraception 18. Severe anemia (Hemoglobin \<10 g/dL) 19. Severe hepatic disease 20. Complex congenital heart disease 21. Listed for cardiac transplantation 22. Other class I indications for pacing