A coronary artery may be unsuitable for bypass<unk>  if it is small (< 1 mm or < 1.5 mm depending on surgeon preference), heavily calcified (meaning the artery does not have a section free of CAD) or intramyocardial (the coronary artery is located within the heart muscle rather than on the surface of the heart).
Although the cardiothoracic surgeon reviews the coronary angiogram prior to surgery and identifies the lesions (or "blockages") in the coronary arteries and will estimate the number of bypass grafts prior to surgery, the final decision is made in the operating room upon examination of the heart and the suitability of the<unk> for bypassing.
Assessment of Target Vessels for Saphenous Vein Grafting
Appropriate use criteria for revascularization
Best practices for transradial angiography and intervention
PCI in the angulated or tortuous lesion
Chronic stable angina risk stratification
Antiplatelet therapy to support PCI
Deep vein thrombosis assessment of clinical probability and risk scores
PCI in the long lesion