Chapter 3 - The Noninvasive Biopsy of Your Arteries
Updated on February 1, 2003

Calcium in Your Arteries Means Plaque in Your Arteries

By now you know that heart attacks and strokes are caused by plaque (atherosclerosis). The more plaque you have, the greater your risk. Before EBCT became available, the only way to measure the quantity of atherosclerosis in your arteries was to perform an autopsy! Not exactly a great way to help you out in advance of a life threatening event. EBCT was developed based on the premise that calcium in the coronary arteries would closely correspond to plaque. This premise was proven by Dr. John Rumberger at the Mayo Clinic. In 1995, he published an article in the official journal of the American Heart Association (Circulation) . He looked at coronary arteries from autopsied hearts. He measured the plaque with the usual staining methods used by pathologists. He then measured the calcium content in the arteries with EBCT. He found an almost perfect correlation between the two kinds of measurements. Very clearly, as plaque content increased, calcium score also increased. Calcium can only form in the arteries as part of plaque formation. For the first time, EBCT gave physicians the ability to diagnose and measure plaque accumulation in the arteries without having to perform an autopsy! I therefore think it’s perfectly appropriate to think of EBCT as a noninvasive biopsy of your arteries. In thirty seconds you can scan a heart and precisely determine the amount of plaque in the coronary arteries. You remain fully clothed and take one deep breath. The radiation exposure is the equivalent of about six chest x-rays, or one fifth the average amount of background radiation received on average each year by Americans.

Soft Plaque and Hard Plaque

You may have heard the terms soft and hard plaque. Many physicians think only soft plaque is dangerous. Since calcium is by definition part of hard plaque (it’s made hard by the calcium), these physicians consider the calcium score irrelevant. In reality, there really is no such thing as pure soft or hard plaque. Each area of plaque is a mixture of both. As plaque gets older, it gets harder, because it becomes more fibrous (fibrous areas of plaque have collagen and calcium). The newer areas have more cholesterol and white blood cells, the older areas have more calcium. The ‘middle-aged’ areas are a mixture of cholesterol, white blood cells, and fibrous tissue. True, the cholesterol-white blood cell mixture (also called the ‘lipid core’) is the most dangerous part of the plaque, because it can rupture through the fibrous part. When this happens, platelets are called into action to form a clot and seal off the soft plaque. The clot may narrow or close off a coronary artery. But even areas with lots of lipid core have some fibrous tissue with calcium close by. So the calcium score accurately reflects the total quantity of plaque. The calcium score is synonymous with ‘plaque burden’. Plaque burden is important because of the intimate relationship between the total amount of plaque and the risk for a plaque rupture.

The Aging of Your Arteries

EBCT, the noninvasive biopsy, tells you two key facts. One, it lets you know if your arteries have calcified plaque. Two, it tells you how much calcified plaque you have. If you don’t have any calcified plaque in your coronary arteries, for example, this automatically puts you into a very low risk group for heart attacks. In our 10,000 patients, about 4,000 had no plaque at all in their coronary arteries. The younger your age, the more likely you are to have a 0 score or a very low score. Why is this? Because age is the strongest risk factor for plaque. As we get older, our arteries show the wear and tear of time. Older arteries are less able to resist the ‘slings and arrows of outrageous fortune’ than young, resilient ones. Also, time represents the cumulative exposure to many potentially harmful substances. Since plaque usually is a one way process, it can only get worse as time goes on. If you are 70 years old, your arteries are more likely to have a higher score than if you are forty years old. Those extra 20 years make a big difference. A small amount of plaque tends to increase in size over time. On the scan images, we see plaque start at the top of the arteries and spread down. We see it also start in one artery and then spread to two or more arteries. We call this plaque progression. If plaque is reduced, we call the process plaque regression.

Your EBCT coronary calcium report should contain two critical pieces of information: a score, and a graph or table comparing you to other men or women in your age group. The score tells you how much plaque you have. The age/gender graph or table helps you determine the age of your arteries. If you are 50 years old but have the same median plaque score as a 65 year old, then your coronary arteries are effectively 65 years old! Your arteries are aging too quickly. Rapidly advancing plaques have a significantly higher risk for heart attack than slowly growing plaques. As we saw in the last chapter, plaque is intimately related to inflammation of the artery wall. When people develop an emergency condition called unstable angina (due to a ruptured plaque causing clot to partially fill a coronary artery), inflammatory white blood cells are found to be activated throughout the coronary blood vessels. Fast growing plaque means lots of inflammation. Slow growing plaque means less inflammation. The aging of the arteries involves chronic inflammation. The more severe the inflammation, the greater the risk for more plaque and for plaque rupture.

Is there a normal amount of plaque associated with aging? Actually, since plaque is a disease process, any amount should be considered abnormal. We compare you to others in your age group and rank you by quartile (in other words, we divide each age group into four sections, from lowest to highest scores). Generally, we look at five year age groups. If you are 52 years old, we would put you in the age group 50-54. The median score in our male patients for that age group was 10.31. This means half the group had scores higher than 10.31 and half the group had lower scores. For women, the median score was 0. Women develop plaque later than men, so the difference is no surprise. What about highest scores for this age group? In men, the highest score we found was 2922. For women, it was 1353. So at any given age, we find a large range of scores.

EBCT Plaque Score Categories

How do you interpret the coronary calcium score? Let’s talk about that for a minute. It’s customary to use five categories when rating the score. The lowest or best category is a score of 0. This means no calcium was seen in the arteries. Since calcium only starts to develop in mid-stage plaque, you could still have plaque in the early stage. Early stage plaque (mostly inflammation with no calcium or lipid core) is generally not prone to rupturing, so your 0 score puts you in a very low risk group for heart attacks. In fact, one study at the Mayo Clinic tracked people with 0 scores for up to five years and found a less than 1% chance of heart attacks in this group.

The next category goes from a score of 1 to a score of 10. This category is called minimal plaque burden. This score means there are tiny areas in the coronary arteries that have progressed to the mid-stage plaque, also called the intermediate lesion, when a calcified shell forms around the fatty part of the plaque. Once you see these small calcified areas, you are seeing the first visible clues to the disease. People in this category have a little more risk for a heart attack than those in the 0 category. The likelihood for a narrowing is still very low, because mid-stage plaques usually don’t rupture.

The next category goes from 11 to 100. This is called mild plaque burden. Instead of just seeing a tiny area in one or two arteries with calcium, we now see denser areas of calcium that have spread a bit down the artery. Two things have occurred as the score goes up. Some areas of plaque have progressed from the inflammatory stage to the lipid core stage, and more of the artery wall is filled with plaque. The lipid core stage means the plaque now has a central core with a highly dangerous mixture of fats, inflammatory cells, and broken down cellular material. At this point, the plaque starts to become more dangerous. One might be able to see mild narrowing on an angiogram, but the likelihood of a severe narrowing is still low.

The next category is called moderate plaque burden and goes from 101 to 400. Usually in this category more than one coronary artery has calcium. The calcium can be seen extending from the top to the middle or lower part of the arteries. Many more areas of later stage plaque are now present. The later stage plaques are called atheromas or fibroatheromas. They have more calcium, and are more prone to rupture because the lipid cores keep growing and may burst through the endothelium which lines the artery wall, separating it from the flowing blood in the artery channel. People in this category have up to seven times the risk for a heart attack or stroke compared with people who have a zero score . They have a 1 in 5 chance of having at least one severely narrowed artery.

The final category is called large or extensive plaque burden. This includes all scores over 400. By now, plaque is usually present in all the major coronary arteries. It may also be seen extending from the top to the bottom in all the arteries. People in this category will have plaque in all stages- early, mid and late. The very late stage plaque has the most calcium, and may in fact be less prone to rupture. This is because a thick layer of fibrous connective tissue (hence the term fibroatheroma) may have developed over the lipid core, making it more difficult for plaque rupture to occur. But arteries with high scores like this will have plenty of areas with the potential for rupture. This category is the most dangerous one to be in, and requires very aggressive treatment. One recent study showed that people with scores over 1000 had a 25% chance per year of having a heart attack or other severe cardiovascular event. No other cardiac test performed as well in identifying the highest risk patients. Another study showed that people with scores over 400 had 28 times the risk for cardiovascular events when compared to people with 0 scores. No other screening test performs as well when trying to identify low, medium and high risk patients.

In the 3D Design chapter you will use 3D F-Diagrams to find you risk category based on the plaque score for your coronary arteries or your carotid arteries. Once you know your risk, you will be able to use the appropriate 3D F-Diagrams for the other risk factors we talk about in the 3D Discover chapter. Those in lower risk groups are advised to follow the 3D Nutrition and 3D Exercise programs. Those in higher risk groups may need to seek medical counsel regarding appropriate medications to lower cholesterol or blood pressure.