2.2 Definitions and Objectives

Coronary CTOs were defined as angiographic evidence of total occlusion with a flow grade 0 Thrombolysis in Myocardial Infarction (TIMI) score in a major epicardial coronary artery of at least 2.5 mm, dating back at least 3 months [3]. The complexity of the CTO lesion and the difficulty of the attempt were evaluated using the J-CTO score [14]. Revascularization was considered complete if, before the CTO PCI procedure, all other hemodynamically significant vessels with a diameter >2.5 mm had been revascularized. Angiographic success was defined as final residual stenosis 30% (by visual estimation) and TIMI flow grade 3 after CTO recanalization. Procedural success was defined as angiographic success without major complications. Major complications were defined as in-hospital death, stroke, peri-procedural myocardial infarction (MI) requiring repeat catheterization, coronary perforation requiring treatment, major bleeding, or major vascular complications. Major vascular complications were defined as retroperitoneal hematoma, acute limb ischemia, and vascular bleeding, which required prolonged hospitalization or transfusion. Type 4 peri-procedural MI was defined as a high-sensitivity troponin T increase of at least 5 times the upper reference limit (URL) (13 ng/L), or a 20% increase and a URL >5 times if it was already elevated before PCI, in combination with ischemic symptoms or ischemic changes on the electrocardiogram (ECG). Contrast-induced nephropathy (CIN) was defined as either an absolute increase in serum creatinine concentration of 0.3 mg/dL compared to the reference concentration, a relative increase in serum creatinine concentration of 50% compared to the reference concentration, or a reduced urinary output of 0.5 mL/kg/hour for at least 6 hours, 24–72 hours after contrast administration. Cardiovascular deaths were defined as deaths caused by MI, sudden cardiac death, death caused by heart failure, deaths caused by stroke or cardiovascular hemorrhage, and deaths caused by other cardiovascular causes. HFH was defined as all hospitalizations caused by the occurrence of heart failure or worsening of pre-existing heart failure. AF was defined as any evidence of AF during the follow-up if AF was not present before or at the time of recruitment. WRF was defined as either the occurrence during follow-up of end-stage renal disease, a decrease of at least 50% in glomerular filtration rate (GFR), or a decrease of more than 30 mL/min/1.73 m2 from the reference level to less than 60 mL/min/1.73 m2 [15]. Follow-up data were censored 4 years after CTO PCI.