Cardiac Shock Wave Treatment in Patients With Reduced Coronary Flow Reserve

Inclusion Criteria: * History of anginal chest pain that prompted a myocardial stress test (nuclear myocardial perfusion imaging, stress echocardiography, or perfusion CMR) * Evidence for stress-induced myocardial ischemia in this examination * Coronary angiogram showing absence of ≥30% stenosis of epicardial coronary arteries Exclusion Criteria: * Participation in other clinical trials * age \<18 years * Contraindications to under cMRI * Contraindications to adenosine (severe chronic obstructive pulmonary disease (COPD), asthma, atrioventricular block (AV block) \> grade 1) * Left ventricular thrombus * Uncontrolled diabetes mellitus * Uncontrolled arterial hypertension, * Any other severe chronic illness such as liver or renal failure (glomerular filtration rate (GFR) \< 45 ml/min), active neoplastic disease, history of myocardial infarction or coronary revascularization within the past three months * Patients with pacemaker or implanted cardioverter defibrillator * Patients after valve surgical replacement * Patients after interventional valve replacement or reconstruction (e.g. transfemoral aortic valve replacement or MitraClip implantation) * Pregnancy (a reliable method of contraception must be used for the entire duration of the study) * Fertile female participants who are capable of bearing children and who do not use a method of contraception that is medically approved by the health authority of the respective country * Missing capacity to consent