Vessel occlusion can be identified by a CT
angiogram or the invasive procedure by a cath
angiogram. Neither test has 100% sensitivity rating, but quite good. Also an EKG can indicate ischemia (lack of blood flow to the heart) that may be due to a vessel blockage.
Usually, the tests aren't given unless there is chest pain, shortness of breath, etc., but if there is a family history of CAD and heart problems the testing for plague occluding vessels may be appropriate.