Studying the prediction ability of different CTO scoring systems on Asian CTO PCI population with their relation to technical success and developing a newer stepwise approach depending on these CTO scoring systems for choosing the suggested successful approach considering collateral channel assessment.

Study of applying the Japenese CTO, Castle and Progress CTO scores on all coronary CTO PCI cohort done at national Taiwan university hospital (NTUH)

Study tools:

1. Basal demographic data collection( age, cardiovascular risk factors, patients clinical data, lesion characteristics, periprocedural complications).

2. The Japanese Chronic Total Occlusion (J-CTO) score calculated for assessment of CTO procedures complexity and predict the likelihood of guide wire crossing within 30 min, as assembled by Morino et al.

   The J-CTO score is the sum of the following 5 binary parameters: blunt proximal cap, calcification, bending >45°, length of occluded segment >20 mm, and previously failed PCI attempt. Each of these independent variables was assigned a value of 1 when present. With increasing probability of difficulty of wire crossing from 0 as easy till 5 as very difficult.

3. Also, the PROGRESS-CTO score calculated (reference website: https://www.progresscto.org/cto with evaluation of 4 baseline angiographic characteristics (proximal cap ambiguity, absence of retrograde collaterals, moderate or severe tortuosity, and LCX CTO) used to determine the likelihood of technical success with CTO PCI. Each of these independent variables was assigned a value of 1 when present. With increasing probability of difficulty of success from 0 as easy till 5 as very difficult.

4. Euro CTO CASTLE scoring calculation

   The CASTLE (coronary artery bypass graft history, age, stump anatomy, tortuosity degree, length of occlusion, and extent of calcification) model applied retrospectively on the patients with every item taking 1 point if present And Technical failure rates range from 8% (CASTLE score 0 to 1) to 35% (CASTLE score ≥4).

5. Collateral assessment including type (septal, epicardial or bypass grafts), size by Werner classification [is graded as: 0, no visible connection between the donor and the recipient coronary artery; 1, thread-like connection between the donor and the recipient coronary artery; 2, side-branch like connection between the donor and the recipient coronary artery], tortuosity degree as by the CC scoring system of the NTUH--> Channel tortuosity caculated as the presence of ≥2 high-frequency, successive curves (within 2 mm) in the context of epicardial collaterals and ≥1 high-frequency curve that failed to uncoil in diastole for septal channels (thus a measure of channel distensibility). A high-frequency curve is defined as a curve that is >180° occurring within a segment length <3× the diameter of the collateral.

And all these scores references and calculation items are mentioned in the references below….

Inclusion Criteria:

• All coronary CTO PCI procedures done at national Taiwan university hospital (NTUH) with their data available for analysis from 2015 till the study data collection step.

Exclusion Criteria:

• Patients whom data not completed

coronary CTO PCI patients done by experienced high volume operator at national Taiwan university hospital (NTUH) with their data available for analysis