Heart failure with preserved ejection fraction (HFpEF) is highly prevalent and associated with impaired functional tolerance, quality of life, morbidity and mortality. Although medical advances have led to effective treatments for heart failure with reduced ejection fraction, there are very limited treatment options for treating HFpEF. While contemporary clinical assessment provides some information beyond ejection fraction in assessment of cardiac function in patients with HFpEF, there is a need to identify biomarkers that associate with pathophysiologic mechanisms of impaired cardiac function. Therefore, we propose to address this knowledge gap by identifying imaging and circulating biomarkers with pathophysiological mechanisms that are associated with exercise tolerance and quality of life in patients with HFpEF. Our specific aim is two-fold: 1) to examine the association of imaging biomarkers of myocardial fiber orientation with exercise tolerance and quality of life and circulating biomarkers in patients with HFpEF, and 2) to examine the association of imaging biomarkers of myocardial energetics with exercise tolerance and quality of life and circulating biomarkers in patients with HFpEF. We will analyze myocardial fiber orientation using a novel diffusion tensor imaging technique in cardiac MRI and myocardial energetics using 31-P magnetic resonance spectroscopy.