This study is undertaken to determine if ticagrelor augments adenosine-induced coronary flow reserve (CFR), ameliorates clinical symptomatology and exercise tolerance in patients with MVA

Considering the reduced CFR and increased platelet aggregability in patients with MVA, together with the augmented effect on adenosine-mediated coronary blood flow and potent antiplatelet effect of ticagrelor, we speculate that ticagrelor can promisingly ameliorate the coronary microvascular function in patients with MVA.

Inclusion Criteria:

For inclusion in the study subjects should fulfill the following criteria:

1. Provision of informed consent prior to any study specific procedures

2. Female or male aged 18-80 years

3. A diagnosis of stable primary MVA based on the presence of

   • a history of typical effort angina,
   • exercise-induced ST-segment depression>1 mm,
   • normal or near-normal (coronary artery stenosis<50%) coronary angiography,
   • absence vasospastic angina
   • a coronary flow reserve (CFR) <2.5 in the left anterior descending coronary artery as assessed by coronary blood flow (CBF) response to adenosine at transthoracic Doppler echocardiography
   • suboptimal control of symptoms on conventional anti-ischemic therapy, as indicated by the occurrence of >1 episode per week of angina

Exclusion Criteria:

ubjects should not enter the study if any of the following exclusion criteria are fulfilled:

1. concomitance with any of the cardiac condition below

   • significant （>50%）coronary plaque disease
   • coronary artery spasm at angiography or other evidence of vasospastic angina
   • valvular or other structural heart disease
   • uncontrolled hypertension
   • abnormal echocardiographic examination including left ventricular hypertrophy

2. no previous consumption of the ticagrelor

3. no apparent contraindications to ticagrelor administration.

   • History of Intracranial Hemorrhage
   • Active Bleeding
   • Severe Hepatic Impairment: AST and ALT are greater than 3 times of the upper limit. Bilirubin is greater than the upper limit.
   • hypersensitivity (e.g. angioedema) to ticagrelor or any component of the product
   • severe COPD or asthma