Abstract 14093: Effects of Continuous Accelerated Pacing on Cardiac Structure and Function in Patients With Heart Failure With Preserved Ejection Fraction: Insights From the MyPACE Randomized Clinical Trial

Introduction: Heart failure with a preserved ejection fraction of 50% or higher (HFpEF) is prevalent and has few evidence-based therapies. In a trial of HFpEF patients with specialized pacemakers, treatment with an accelerated personalized pacing rate averaging 75 bpm (myPACE) markedly improved quality of life, NT-proBNP, physical activity, and atrial fibrillation burden compared with the standard lower rate setting of 60bpm (usual care). Methods: Provider-initiated echocardiographic studies obtained before and after the trial were assessed for changes in left ventricular (LV) structure and function amongst participants who continued their pacing assignment. The analytic approach aimed to detect differences in standard and advanced echocardiographic parameters within and between study arms. Results: Of the 100 trial participants, 16 patients in the myPACE arm and 20 in the usual care arm had a qualifying set of echocardiograms with a mean±SD time of 3.7±2.0 years apart. Heart rates were expectedly higher among myPACE patients after the trial (in bpm: myPACE 75±6 vs. usual care 65±7, p<0.001). Sustained exposure to moderately accelerated pacing resulted in a reduced septal wall thickness (myPACE 1.07±0.05mm vs usual care 1.23±0.04, p=0.008) and a lower LV mass to systolic volume ratio (myPACE 1.52±0.09 vs. usual care 1.84±0.05, p=0.038) accompanied by a small reduction in LV ejection fraction (in %: myPACE 55±1 vs usual care 60±1, p=0.015). These changes were paralleled by marked improvements in heart failure-related quality of life (MLHFQ points: myPACE 17±21 vs usual care 28±22, p<0.001). Markers of diastolic function and LV performance were not affected. Conclusions: Exposure to continuous accelerated pacing in HFpEF is associated with a reduced LV wall thickness and a lower mass to systolic volume ratio and ejection fraction that remained within normal limits.