This portion of HFpEF consists predominantly older age and high prevalence of co-morbidity such as overweight/obesity, diabetes mellitus, hyperlipidemia, metabolic syndrome and hypertension. The systemic pro-inflammatory state may induce coronary endothelial inflammation, microvasular dysfunction, myocardial substrate shift, myocardial and interstitial fibrosis that contribute to high diastolic left ventricular stiffness and HF development. Myocardial metabolic and perfusion imaging is a vital tool for understanding the physiologic consequences of HF. Absolute myocardial blood flow (MBF) and myocardial flow reserve (MFR) provide incremental diagnostic and prognostic information over relative perfusion alone. Recent development of dedicated cardiac SPECT cameras with better sensitivity and temporal resolution make dynamic SPECT imaging more practical. Quantitative 18F-FDG PET could be used as a means to measure myocardial metabolic changes. The study investigators propose that microvasular dysfunction and abnormal metabolic substrate shift precedes and triggers the onset of diastolic dysfunctions. The potential roles of myocardial perfusion and metabolic abnormalities in subjects with cardiovascular risks, metabolic disease and HFpEF assessed by nuclear dynamic imaging warrant further investigations.