The chronic total occlusion of a coronary artery is the most frequent cardiac disease in the developped countries. The percutaneous coronary intervention is one of the existing treatments. This procedure is long, expensive and uses a lot of contrast medium and X ray. With this study, the investigators want to adress the impact of CT scan performed before the surgical procedure. A better knowledge of the patient's anatomy could lead to a better success rate of the operation, with a lower radiation, lower contrast injection, and a faster and more cost-efficient procedure.

A chronic total occlusion (CTO) is the complete obstruction of a coronary artery that has been established from more than 3 months with TIMI (Thrombolysis in Myocardial Infarction) 0 flow. This is a frequent pathology, demonstrated in 20% of patients studied with a coronary angiography. The patients affected by an isolated CTO or by a multi-vascular coronary disease with one or more CTO are an heterogenous population in relation to age, co-morbidity, risk factors.

The treatment of this disease is medical, interventional or surgical. The interventional option is often the first choice in case of symptoms or ischemia associated with viability of the myocardial wall, originally perfused by the occluded segment. Medical treatment is often not enough to reduce symptoms and to improve quality of life. Surgery is very invasive, especially for patients with mono-vascular disease, not always possible, especially in case of distal diffuse disease or heavy co-morbidity.

The Percutaneous Coronary Intervention (PCI) is a good option thanks to the improvement of materials and recanalization techniques (anterograde, retrograde and dissection re-entry). However, the procedure is often long, expensive, using a lot of contrast medium and X ray.

At the diagnosis stage of a CTO, the Japan Chronic Total Occlusion (J-CTO) score defines the complexity of the procedure : 0 easy, 1 intermediate, 2 hard, ≥ 3 very hard. The score is actually calculated with the angiography data after evaluation of the occlusion's proximal cap shape, presence of calcifications in the occluded segment, tortuosity of the occluded segment and length of the occlusion.

In addition to the angiography data, a CT scan of coronary artery can be performed as part of Standard of Care. In the study's coordinating center, more than 2000 CT scans are performed by the team of interventional cardiologists. Data generated from last generation CT scan are then interpreted to extrapolate informations about the occluded segment, the occluded artery and the contralateral artery.

CT scan is able to identify very well the calcium distribution in the occluded segment/artery, the true length of the occlusion, bends, collateral branches, distal vessel anatomy, coronary path and more, solving ambiguity of proximal cap and showing the shape of the distal cap. Thanks to this investigation, the investigators can better evaluate the J-CTO score and the CT Rector score. The CT Rector score is helping to grade the CTO difficulty before the PCI by predicting time-efficient guidewire crossing. The investigators can calculate the calcium score of the occluded artery to detect a critical value for the success of CTO PCI. The best strategy with appropriate material can then be chosen for the procedure PCI.

In this study, the investigators would like to demonstrate the interest in performing a CT scan as a part of the pathology diagnosis before the PCI in more complex occlusions (J-CTO score ≥ 2). The investigators think that the CT scan, with a last generation GE Revolution 256 slice machine, is actually the best method to evaluate the J-CTO score, the CT Rector score and to obtain other important information like anatomical position of the occluded artery and presence of side branches in the occluded segment.

A better evaluation of J-CTO score and complex anatomy will then allow the selection of the best technique for the procedure with probably a better success rate, lower radiation, lower contrast injection, and a faster and more cost-efficient procedure.

Inclusion Criteria:

1. Male or female ≥ 18 years old and ≤ 90 years old,
2. BMI ≤ 40 kg/m²,
3. Dated and signed informed consent, before any study-related procedures
4. Ability to understand and comply with the study procedures,
5. Affiliate or recipient of a social security scheme,
6. Coronary artery chronic total occlusion (TIMI 0 flow from > 3 months) associated with myocardial viability (intended like normokinetic/hypokinetic wall motion or instrumental data in favor of viability) associated with ≥ CCS2 angina or ≥ NHYA2 dyspnea or documented ischemia or ejection fraction <50%.
7. Coronary angiography J-CTO score ≥ 2 (complex cases)

Exclusion Criteria:

1. Pregnant or breastfeeding woman,
2. Adults patients protected by law,
3. Very frequent and irregular cardiac rhythm (>100/min.),
4. More than one CTO to be treated by PCI,
5. Coronary angiography J-CTO (Japan Chronic Total Occlusion) score 0/1
6. Hemodynamic instability,
7. Anemia < 9g/dl,
8. Gastrointestinal bleeding,
9. Thrombocytopenia with < 50 000/mm3 platelets count,
10. Severe valvular disease associated
11. CT-Scan performed as part of the standard of care pathology diagnosis, before the inclusion