Personalized Pacing: A New Paradigm for Patients With Diastolic Dysfunction or Heart Failure With Preserved Ejection Fraction

Inclusion Criteria: * Implanted pacemaker with either 1) intrinsic ventricular conduction or 2) conduction system or biventricular pacing or 3) RV pacing \<2% and paced QRS duration \<150ms * Clinical evidence of heart failure with preserved ejection fraction or diastolic dysfunction, based on: * dyspnea with exertion * or NYHA Class ≥ II heart failure * or pulmonary edema on prior chest imaging or documented on exam * or is taking loop diuretics for heart failure * or had NTproBNP \>400 ng/ml in the last 24 months * or a heart failure hospitalization in the last 2 years * or has diastolic dysfunction on echo * or has left ventricular hypertrophy on echo * or has left atrial (LA) dilation (LA volume/BSA index \>28ml/m2) Exclusion Criteria: * Left ventricular ejection fraction \< 50% * Life expectancy \< 12 months * Symptomatic pulmonary disease on home oxygen * Uncontrolled hypertension as defined by blood pressure \>160/100 mmHg on two checks ≥15 minutes apart * Hypertrophic cardiomyopathy * More than moderate valvular disease * Aortic valve replacement \< 1 year * Angina pectoris * Creatinine \> 2 * Hemoglobin \< 8 g/dL * Participation in another clinical trial or registry study * Inability to follow up for regularly scheduled pacemaker appointments or to follow up for this study * Pregnant patients or patients of childbearing age without reliable contraceptive agent (intra-uterine device, birth control implant, compliance with contraception injections or contraception pills) for the duration of study participation