Coronary chronic total occlusions (CTOs) are defined as an occluded coronary vessel with TIMI defined as an occluded coronary vessel with TIMI (Thrombolysis in Myocardial Infarction) grade flow 0 and an estimated duration of at least 3 months. They are frequently encountered in patients undergoing coronary angiography. The application of contemporary techniques and the use of advanced dedicated equipment lead to high procedural success and low adverse events rates in experienced centers. Fractional flow reserve (FFR) is a validated tool to assess physiological severity of coronary artery disease and have a prognostic role after percutaneous coronary intervention (PCI). SPECT (Single-Photon Emission Computed Tomography) is the golden standard for detection of myocardial ischemia. Recanalization of a CTO leads to a number of anatomical and pathophysiological changes to the coronary circulation. These include anatomical and functional collateral vessels regression and significant lumen enlargement because of recovery of blood flow and restoration of vasomotor tone. The effect of PCI on CTO is unknown. The aim of this study was to assess the functional result of CTO PCI by measuring FFR and D SPECT before and immediately post-CTO PCI and at short-term follow-up.

Coronary chronic total occlusions (CTOs) are defined as an occluded coronary vessel with TIMI defined as an occluded coronary vessel with TIMI (Thrombolysis in Myocardial Infarction) grade flow 0 and an estimated duration of at least 3 months. They are frequently encountered in patients undergoing coronary angiography. The application of contemporary techniques and the use of advanced dedicated equipment lead to high procedural success and low adverse events rates in experienced centers. Fractional flow reserve (FFR) is a validated tool to assess physiological severity of coronary artery disease and have a prognostic role after percutaneous coronary intervention (PCI). SPECT (Single-Photon Emission Computed Tomography) is the golden standard for detection of myocardial ischemia. Recanalization of a CTO leads to a number of anatomical and pathophysiological changes to the coronary circulation. These include anatomical and functional collateral vessels regression and significant lumen enlargement because of recovery of blood flow and restoration of vasomotor tone. The effect of PCI on CTO is unknown. The aim of this study was to assess the functional result of CTO PCI by measuring FFR and D SPECT before and immediately post-CTO PCI and at short-term follow-up.

Inclusion Criteria:

• age >18 years old
• single CTO lesions, or other stenosis have been PCI treated for more than one months
• the diameter of target vessel ≥2.5mm
• stable angina pectoris, or myocardial ischemia in the area of CTO lesions
• the patients agree to this research plan and sign the consent form, and complete the follow-up

Exclusion Criteria:

• Acute myocardial infarction in one month
• In addition to the area of CTO lesions, there are serious untreated coronary lesions
• bridge vascular CTO lesions
• untreated coronary artery or cardiac surgery due to interventional complications, or intraoperative death
• acute decompensated heart failure
• allergies to contrast or radionuclide tracers
• patients with planned pregnancies or lactation or 1 years after intervention
• malignant neoplasms or life expectancy of less than 1 years
• patients plan of surgery
• patients cannot tolerate double antiplatelet therapy for at least 12 months
• any condition that does not fit coronary intervention or is a drug-eluting stent

patients of single coronary chronic total occlusion