fries, eggs, butter, desserts, ice cream. your cholesterol number is a good measure of what's in the blood. but here's the problem -- it doesn't tell if you it is building up in the walls of your blood vessels forming plaque. it's the plaque that causes heart attacks. >> if you look in the coronary care unit at people that have heart attacks, the cholesterol levels of those who have heart attacks versus those in the street who have it are essentially the same. >> that is kind of surprising. right? because you'll hear people exchanging their cholesterol numbers. if it is low they seem quite proud of it. if it is high, there's cause for concern. you say that that's -- you know what? you're not looking in the right place. >> that's essentially useless. >> here's what does matter, he says. the size of your ldl, or bad cholesterol particles. larger ldl particles don't pose much of a threat because they pass through the blood vessels without sticking. it is the smaller ldl particles that are more likely to lodge in the walls of blood vessels and cause a build-up of plaque. >> if they're small, you can have a lot of little particles that penetrate the vessel wall more easily. there are a lot of little old ladies in their 80s with very high cholesterols who have squeaky clean vessels. they have very large cholesterol particles and they don't get in to the vessel wall. >> so you have to ask about the size of the particles as well when it comes to bad cholesterol. >> yes. >> that's why the doctor wants a blood sample. >> i don't think anyone likes getting their blood drawn. >> he wants to find out if i have a lot of small ldl particles. a sign that i could be prone to building up plaque no matter what my overall cholesterol number is. coming up -- >> i was incredibly lucky that something more severe didn't happen. >> lessons from former president clinton. >> and pictures don't lie. i learn if my arteries are young or old. time to find out what fate has