All participants or their family members were informed about the potential publication of their identities and images, and all of them completed consent forms. All procedures and protocols were approved by the ethics committee of Beijing Anzhen Hospital, Capital Medical University, and the experiments were conducted in accordance with the Declaration of Helsinki (1975 and subsequent revisions).
Between January 2016 and December 2018, 450 unstable angina patients (350 men and 100 women) who underwent successful PCI treatment for CTO lesions in Beijing Anzhen Hospital were enrolled in this retrospective study. Clinical and angiographic follow-up was performed in all patients for 12 months. The inclusion criteria were as follows. (1) ≥18 years old. (2)Coronary angiography indicated that an occlusive (100% stenosis) coronary lesion with anterograde Thrombolysis In Myocardial Infarction 0 flow for at least 3 months,and only one NCTOL was found.（3）All patients underwent successful PCI treatment for CTO lesions.（4）There was no contraindication for anticoagulation and antiplatelet therapy.
All patients were divided into non chronic total occlusion lesions(NCTOL) progression group ( 205 cases) and the control group (275 cases) according to angiographic follow-up outcome in 12 months.
The main exclusion criteria included the following: previous percutaneous coronary intervention (PCI) in CTO artery (n = 6)， CTO artery with excessive proximal tortuosity or severe calcification (n = 14), left ventricular ejection fraction <35% (n = 15), lack of clinical and angiographic follow-up (n = 26), in-hospital death after PCI (n = 11), myocardial infarction within 2 w of PCI to exclude potential subacute stent thrombosis of the intervened arterial segment (n = 9), and repeated PCI of CTO lesions for restenosis or progression (n = 43).
Coronary angiography was performed using the Judkins method, and coronary artery lesion classification was based on the American College of Cardiology/American Heart Association guidelines .Stents were implanted using a routine method, and the procedure succeeded with residual stenosis <20%, TIMI flow grade of 3 and no acute complications (death, myocardial infarction, emergency coronary artery bypass grafting (CABG)), and no major adverse cardiac events (cardiac death, myocardial infarction, target vessel revascularization). Clinical and angiography follow-up was performed for 12 months.
NCTOLs were defined as those with a diameter of stenosis <70%. All patients underwent PCI for the CTO lesions.
Quantitative coronary angiography was performed during the first angiography. Follow-up angiography was performed by two independent investigators who were blinded to the results. We categorized the lesions in accordance with the American College of Cardiology/American Heart Association. Classification was performed on the basis of the morphological characteristics of lesions that cause significant stenosis of the coronary arteries. These include two categories of simple lesions (A or B1 lesions) and complex lesions (B2 or C).
The collected data included demographic information, medical history, coronary artery disease risk factor status, detailed coronary angiographic information, biomarkers associated with coronary atherosclerosis at the time of baseline PCI, and coronary angiographic information at the time of angiographic follow-up.
All clinical, laboratory, and coronary angiographic data were evaluated by two independent investigators who were not involved in the angiographic procedures.
Definition of NCTOL progression : 1. The stenosis degree of the NCTOL was ≥50% at the time of baseline PCI, and the degree of NCTOL progression was ≥10% at the time of angiographic follow-up. 2. The stenosis degree of the NCTOL was <50% at the time of baseline PCI, and the degree of NCTOL progression was ≥30% at the time of angiographic follow-up. 3. The degree of NCTOL progression ≥30%, while there were no NCTOLs at the time of baseline PCI. 4. NCTOL progression to total occlusion.