Could a smart pacemaker ease a common type of heart failure?

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Diagnosis of Heart Failure, Left Ventricular Ejection Fraction (LVEF) ≥ 55% (this and other measurements must be made within the last year). * New York Heart Association (NYHA) Functional Class I-III * Stable on guideline-directed medical therapy (GDMT) heart failure medications as determined by the investigator, for at least 1 month, with the exception of loop diuretic therapy. GDMT should be in accordance with current American Heart Association (AHA)/American College of Cardiology (ACC)/Heart Failure Society of America (HFSA) Guidelines and include consideration of Sodium/glucose cotransporter-2 inhibitors (SGLT2i) therapy. * V End Diastolic Volume indexed to body surface area (BSA) ≤ 80 mL/m\^2. * Concentric remodeling or concentric hypertrophy defined as at least one of the following criteria: * Left ventricular (LV) posterior or lateral wall thickness \> 11mm * Relative wall thickness (RWT) \> 0.42 * Male and LV mass indexed to BSA ≥115 g/m2 * Male and LV mass indexed to height ≥ 49.2 g/m2.7 * Female and LV mass indexed to BSA ≥ 95 g/m2 * Female and LV mass indexed to height ≥ 46.7 g/m2.7 Exclusion Criteria: * Unable or unwilling to undergo contrast MRI. * Class I indication for permanent pacing, except for symptomatic chronotropic incompetence * Current permanent or persistent Atrial fibrillation (A-fib) * Structural heart disease requiring intervention * Aortic valve replacement procedure less than 12 months prior to enrollment * Known pericardial constriction, genetic hypertrophic cardiomyopathy, or infiltrative cardiomyopathy * Severe aortic or mitral valve disease, defined as severe regurgitation or a valve area \< 1cm\^2 * Exertional angina * Severe pulmonary disease including severe Chronic obstructive pulmonary disease (COPD) (i.e., requiring home oxygen, chronic nebulizer therapy, or chronic oral steroid therapy or hospitalized for pulmonary decompensation within 12 months) * Estimated glomerular filtration rate (eGFR) \< 25 ml/min/1.73m\^2 as calculated by the Modification in Diet in Renal Disease (MDRD) formula * Uncontrolled blood pressure, defined as systolic pressure outside the range of 100 to 160 mmHg despite anti-hypertensive medication.