Physiologic Accelerated Pacing as a Treatment in Patients With Heart Failure With Preserved Ejection Fraction

Part I: Week 0-12: Quantify the effects of lower heart rate (HR) elevation on symptoms and function in patients with heart failure with preserved ejection fraction (HFpEF). The investigators hypothesize that a personalized lower HR elevation employing physiological conduction system pacing in patients with HFpEF will decrease left atrial and left ventricular filling pressures. The investigators expect that this will result in a symptomatic and functional improvements and reduce NTproBNP levels. Additionally, HR elevation may have the potential to reduce the risk for heart failure hospitalization, atrial fibrillation (AF), and cerebrovascular stroke as these outcomes are increased in patients with a normal or preserved ejection fraction on HR lowering treatments. After undergoing pacemaker implantation participants will be randomized to one out of three treatment arms (a) Bachmann's bundle pacing, (b) Bachmann's bundle and His bundle pacing, (c) no pacing with cross-over to alternative treatment arm at week 4 and 8, respectively. The lower pacing rate in arms a and b will be programmed to the personalized lower heart rate for 24 hours a day (the patient's intrinsic heart rate can exceed the personalized lower rate limit). Part II: Week 13-20: Determine the effects of nocturnal heart rate elevation on symptoms and function in patients with HFpEF. The investigators hypothesize that a moderate HR elevation to 110bpm delivered for 10 hours between 8PM to 6AM will provide additional hemodynamic benefits and will lead to beneficial ventricular remodeling. After week 12 the participant will undergo randomization to one of two treatment arms (a) Bachmann's bundle and His bundle pacing, (b) Bachmann's bundle pacing, His bundle pacing and nocturnal pacing. The participant will cross-over to the other treatment arm after 4 weeks (study week 16).