Coronary microvascular angina (MVA) significantly reduces quality of life and increases the risk of heart problems in patients with angina. Unfortunately, there are no effective treatments available yet. The endothelin-1 (ET-1) - endothelin receptor (ETRs) system plays a critical role in MVA. Preclinical studies demonstrate that ETRs antagonists or pericyte-specific knockdown of ETRs can improve coronary microvascular function in myocardial ischemia/reperfusion mice and diabetic mice. Foreign clinical drug trials have shown that ETRs antagonists may alleviate patients' symptoms. However, these studies predominantly rely on conventional coronary angiography rather than direct assessment of coronary microvascular function. Early experimental trials using ETRs antagonists reported a high incidence of side effects, such as sodium retention and headaches, which negatively impacted treatment satisfaction. To address these limitations, a pilot study is proposed to evaluate the efficacy of macitentan in MVA treatment. This investigation will implement thermodilution-based coronary microcirculation function testing to precisely characterize the severity and subtype of coronary microvascular lesions in MVA patients. By administering macitentan - a safer ETRs antagonist - the study aims to systematically assess improvements in coronary microvascular function, angina symptom relief, and adverse event incidence. The findings are expected to provide critical evidence regarding the therapeutic potential and safety profile of macitentan, while establishing foundational data for subsequent large-scale clinical trials.