Rationale and Study Design of Differences in Cardiopulmonary Exercise Capacity According to Coronary Microvascular Dysfunction and Body Composition in Patients with Suspected Heart Failure with Preserved Ejection Fraction

Coronary microvascular dysfunction (CMD) is one of the mechanisms of myocardial ischemia and left ventricular (LV) diastolic dysfunction, which is closely related to heart failure with preserved ejection fraction (HFpEF). Frailty, associated with sarcopenia, is often accompanied by HFpEF. In the present study, we aim to evaluate the relationship between CMD, body composition, and cardiopulmonary exercise capacity in patients with suspected HFpEF. We will enroll patients experiencing chest symptoms (chest pain or dyspnea) with an indication of non-obstructive coronary artery disease (<50% stenosis) on coronary angiography and preserved LV ejection fraction (≥50%) on echocardiography. All patients will undergo body composition analysis and adenosine stress echocardiography with the evaluation of coronary artery blood flow and maximal oxygen consumption by cardiopulmonary exercise test. LV end-diastolic pressure will be assessed using coronary angiography. Coronary flow reserve (CFR) is defined as the ratio of the peak to the baseline mean diastolic velocity of coronary blood flow. A CFR <2.3 is defined as coronary microvascular dysfunction. The correlation of CFR and body composition with LV diastolic function and cardiopulmonary exercise capacity will be assessed. This trial will suggest the specific phenotypes of HFpEF according to body composition and CMD and the specific management of the different phenotypes of HFpEF.