Mechanical Dyssynchrony and Microvascular Dysfunction by SPECT

Inclusion Criteria: * Ischemia with no obstructive coronary arteries (INOCA) * Obstructive coronary artery disease (CAD) * Patients without evidence of coronary heart disease Exclusion Criteria: * Left ventricular ejection fraction \<55% according to echocardiography; * History of myocardial infarction/revascularization; * hypertension: systolic blood pressure \>180 mm Hg. Art., diastolic BP\>110 mm Hg. Art.; * systolic arterial hypotension \<80 mm Hg. Art.; * atrial fibrillation; * AV blockade of the III degree; sick sinus syndrome; * massive pulmonary embolism (PE) with a high degree of pulmonary hypertension; * the presence of significant valvular pathology (mitral insufficiency ≥ 3 degrees, aortic insufficiency ≥ 3 degrees, tricuspid regurgitation ≥ 3 degrees). * severe course of bronchial asthma, chronic obstructive pulmonary disease; * decompensated type 2 diabetes, * severe liver or kidney failure (glomerular filtration rate \<50 ml/min/1.73 m3 (CKD-EPI), * morbid obesity (body mass index \>45); * history of myocarditis * indications of poor drug tolerance; * oncological diseases; * chronic alcoholism, mental disorders; * other severe comorbidity, * refusal to participate in the study.