Inclusion Criteria:  Age ≥ 18 years old Chronic refractory angina refractory to medical and interventional therapies. At least one open coronary artery (excluded right coronary artery) where to performs IMR evaluation Ability to provide informed written consent Life expectancy ≥1 year  Exclusion Criteria:  Recent (within 3 months) acute coronary syndrome Left ventricular ejection fraction of <30% Severe valvular heart disease Inability to perform IMR Technical contraindications to the implant ( A pacemaker electrode in the coronary sinus, Mean right atrial pressure >15mmHg, Anomalous coronary sinus anatomy)