All pts with high cholesterol will not have severe blockages, they have high probability that they might develop blockages over time period. So if you know that your cholesterol is high you should take treatment for that this way you can prevent those problems. If blockage is there even if unknown pt can get symptoms on exertion. Degree of Symptoms depends on percentage of blockage and whole other factors.. Pt usually come to doctor with symptoms then he will undergo coronary angiography and you will get to know the percentage of blockage and number of blockages.