The pathophysiologic aspects of heart failure with maintained ejection fraction may be influenced by coronary artery disease (CAD) and coronary microvascular dysfunction (CMD) (HFpEF). The prevalence of CAD and CMD, on the other hand, has not been thoroughly investigated. For a study, the researchers wanted to determine how often CAD and CMD were in hospitalized HFpEF patients. A Prospective, multicenter cohort research evaluated a total of 106 consecutive patients hospitalized with HFpEF between January 2, 2017, and August 1, 2018, with data processing taking place from March 4 to September 6, 2019. Following coronary angiography, participants had coronary vasoreactivity testing and a guidewire-based assessment of coronary flow reserve, index of microvascular resistance, and fractional flow reserve. Extracellular volume was measured using cardiac magnetic resonance imaging with late gadolinium enhancement. The myocardial-perfusion reserve index was used to quantify myocardial perfusion both qualitatively and semiquantitatively. Myocardial ischemia, infarction, and fibrosis are all common causes of obstructive epicardial CAD, CMD, and myocardial ischemia, infarction, and fibrosis. 75 had coronary angiography, 62 had coronary microvascular function assessment, 41 had coronary vasoreactivity testing, and 52 had cardiac magnetic resonance imaging of the 106 individuals (53 [50%] women; mean [SD] age, 72  years). In 38 of the 75 patients, obstructive epicardial CAD was present (51%, 95% Confidence interval, 39% -62%); 19 of the 38 (50%, 95% CI, 34% -66%) had no history of CAD. In 41 of the 62 subjects, endothelium-independent CMD (i.e., coronary flow reserve less than 2.0 or index of microvascular resistance more than or equal to 25) was found (66%; 95% CI, 53% -77% ). In 10 of the 41 patients, endothelium-dependent CMD (abnormal coronary vasoreactivity) was found (24% ; 95% CI, 13% -40% ). Overall, 45 of 53 participants (85%; 95% CI, 72% -92%) had CMD, while 29 of 36 (81%; 95% CI, 64% -91%) of those who did not have obstructive epicardial CAD had CMD. Myocardial-perfusion reserve index less than or equal to 1.84 (ie, impaired global myocardial perfusion) was found in 29 of 41 patients (71%; 95% Confidence interval, 54% -83%), visual perfusion defect was found in 14 of 46 patients (30%; 95% Confidence interval, 19% -46%), and ischemic late gadolinium enhancement (ie, myocardial infarction) was found in 14 of 52 patients (27%; 95% (42% ; 95% CI, 28% -56% ). Patients with obstructive CAD experienced more adverse events (28 [74%]) during follow-up than those without obstructive CAD (17 [46%]). 91% of patients with HFpEF had evidence of epicardial CAD, CMD, or both in the cohort research. CMD was found in 81% of patients without obstructive CAD. In hospitalized patients with HFpEF, obstructive epicardial CAD and CMD appear frequent and often undetected and may be therapeutic targets.