REmodeling the Left Ventricle With Atrial Modulated Pacing

Inclusion Criteria: * Subject has had a market released dual chamber Medtronic Pacemaker with a Sleep function for at least 3 months * Subject is stable on current medications * Subject has dyspnea with exertion or diagnosed as New York Heart Association (NYHA) Class II or III Heart Failure * Subject has had a prior Echo in past 6 months with: Ejection Fraction (EF) ≥ 50% and Diastolic volume \<80 ml/m² * Subject has evidence of hypertrophy (indexed to body surface area: men 115 g/m², women 95 g/m² or indexed to height: men 49.2 g/m2.7, women 46.7 g/m2.7) or Relative Wall thickness \>0.42, or Wall Thickness\>1.2cm (posterior wall) * Subject is willing to sign and date the study Informed Consent Form (IC Form) - Subject is 18 years of age or older, or of legal age to give informed consent per local law * Subject is expected to remain available for follow-up visits Exclusion Criteria: * Subject has permanent atrial fibrillation (AF) or AF noted on baseline interrogation rhythm strip * Subject has uncontrolled BP; (systolic pressure needs to be \>100 mmHg and \<160 mmHg on medications) * Subject has severe stenosis of the aortic or mitral valve, defined as valve area ≤1.0 cm² or severe regurgitation of the aortic or mitral valve * Subject has symptomatic Chronic Obstructive Pulmonary Disease (COPD) requiring oxygen * Subject's Pacemaker has less than 6 months of Pacemaker battery life * Subject had an aortic valve replacement (surgical or TAVR) procedure less than 9 months prior to enrollment * Subject's programmed upper rate limit is less than 100 bpm because of concerns of elevated pacing * Subject is unable or unwilling to perform the 6 Minute Walk Test at all scheduled study visits * Subject is currently enrolled or planning to enroll in a potentially confounding trial during the course of the study (co-enrollment in concurrent studies is only allowed when documented pre-approval is obtained from the Medtronic study manager) * Subject is pregnant * Subject meets any exclusion criteria required by local law * Subject's life expectancy is less than 12 weeks * Subject with medical condition that precludes the patient from participation in the opinion of the investigator * Subject has known coronary disease with Class II angina