Why Assess for Coronary Calcium?
The value of coronary calcium scoring is that is allows the practitioner to look inside the heart to know who to treat for coronary artery disease. External physical presentations can be deceptive for actual coronary artery disease presence. With knowledge of the actual extent of the coronary artery disease then tailored lifestyle, diet, exercise, nutrient and drug interventions can be implemented to more effectively reduce the risk of disease progression or expression of a coronary event.
What is Atherosclerosis and What Happens to the Artery?
Atherosclerosis means hardening of the arteries. It is the exact same process as bone formation. The coronary arteries are like hoses. You turn on the water and some of the water is absorbed by the hose, and then it stretches or dilates. Then water eventually squirts out of the end of the hose. But it doesn’t right away. With calcification or stiffening of our arteries (atherosclerosis) the blood shoots through the arteries at a greater pressure which causes damage to the blood vessel and causes plaques to rupture. A hard stiff artery is not a healthy artery.
How Does Plaque Get Created? What is the Difference Between Microvascular and Macrovascular Plaque Rupture?
Microvascular ruptures of plaque occur (not “macrovascular” plaque rupture which can lead to a heart attack or stroke) and the body tries to protect itself by walling off the plaque (lipid rich core) with calcification, so it can’t communicate with the blood vessel so you won’t get a macrovascular plaque rupture. Over time these small microvascular ruptures result in a signiﬁcant amount of calcium being laid down and stiffening of the artery (atherosclerosis). The “macrovascular” plaque ruptures, which penetrate the endothelium and cause a clot, can result in a heart attack or stroke occurs after a significant number of these microvascular plaque ruptures occur. So preventing further microvascular ruptures, leading to coronary calcification, reduces the risk of a large plaque rupture.
Coronary Calcium is the “Tip of the Iceberg” of Coronary Artery Disease
If you have a lot of coronary calcification you have a lot of soft and fibrous plaque and a lot of atherosclerosis in the arteries.
The coronary calcium score is usually only assessed over the age of 35-40 because until then the individual may only have a significant amount of soft plaque but it hasn’t calcified yet. The calcified plaque seen with the coronary artery calcium scoring (CAC) usually represents about 20% of the total plaque burden (or “tip of the iceberg”) with the latter 80% being the three forms of soft plaque that are more likely to rupture which is not seen with the CAC testing. Soft plaque is only seen with CT angiography which is essentially the same test as the CAC testing with the same machine but you just get an iodine containing contrast dye which allows for the soft plaques to be seen as well.
The patient that has more “microvascular” plaque ruptures is more at risk to have a “macrovascular” plaque rupture which can lead to a heart attack, stroke or death.
Why Do CT Angiography?
In the preventive world you want to stay with CAC testing to determine who is at risk of a stroke, heart attack or sudden death from multiple microvascular ruptures that could lead to a macrovascular rupture. A CT (computerized tomography) angiogram (CTA) is used in a patient who is having symptoms to determine if they have coronary artery disease or not, and is excellent at diagnosing “stenosis” or tightening of the coronary artery. CTA is excellent at determining whether it is coronary or non-cardiac chest pain. CTA is a diagnostic tool for coronary artery stenosis while CAC is a prognostic test for coronary artery disease. You can have significant coronary calcification without stenosis in possibly an exerciser and someone who had been living a good lifestyle. If the person is without coronary symptoms do CAC testing, if symptomatic do a CT angiogram to determine if the cause is cardiac or not.
Types of Soft Plaque (non-calcified plaque)
There are 3 types of soft plaque:
1) Low attenuation plaque, the necrotic core, is pure lipid. It is the most inflamed, pathological and most likely to rupture plaque. It is probably the most dangerous type of plaque.
2) Fibro – fatty plaque – has more fibrous tissue. It is more stable and less likely to rupture.
3) Fibrous plaque – may be protective. It walls off the top of the plaque from the artery. This thin layer walls off the soft plaque from the wall of the artery. This fibrous wall can thicken, and protect against plaque rupture.
These three types of plaque can be seen with CT angiography. It is not clear yet whether a stent might be put in if someone has too much of the low attenuation plaque.
Inflammation Markers – Lipoprotein-associated phospholipase A2 (Lp-PLA2) and Myeloperoxidase (MPO) Dr. Budoff has more experience with Lp-PLA2 and there has been more studies done with this inflammatory marker compared to MPO. The timing of their use may be of significant value in indicating short-term increased risk, and the reduction of imminent risk either by chance or some type of medical or lifestyle intervention. These two markers may be very valuable in following increasing and decreasing risk in the short-term but needs more study. They may be valuable in following a new therapeutic intervention over several months instead of waiting a year or so to repeat a coronary calcium score (CAC).
Vascular Function Testing
Another way to follow a therapy to see if the intervention is having a positive short-term effect is endothelial function testing (brachial reactivity testing) which can measure the effects of a meal on arterial reactivity within hours.
Artery Stiffening (Thickening) as a Cardiac Risk Factor
Artery stiffening is a negative risk factor for cardiac health. An stiffened artery increases the speed that blood flows through the arteries and it is a marker of end organ disease. A more rapid speed of blood flow can be measured and is a negative with regards to cardiac health.
Is Carotid Intimal Media Thickness (CIMT) Testing of Value for Coronary Risk?
Carotid Intimal Media Thickness (CIMT) testing is not the optimal test for evaluating atherosclerosis. It is mostly measuring the media thickness. The media is much thicker than the intima. The intima is where the atherosclerosis occurs. So the CIMT misses most of this. 80% of what it is measuring is the normal wall of the carotid artery. CAC scoring is a much more accurate assessment of coronary artery risk. CIMT really is outdated for this evaluation.
Stroke Risk Assessment?
For evaluating the carotid arteries Doppler ultrasound is valuable looking for plaque and stenosis and may be a better tool than CAC scoring for evaluating stroke risk.
What is the CAC Radiation Exposure?
It is the same as a mammogram about .5 millisievert. Background radiation in Los Angeles for a year is 2.5 millisievert. If you are a 50 year-old person and you get a CAC test you now have the exposure of 50 years plus 3 months which is trivial compared to the overall things we do. A stress nuclear test for the heart is much higher, 16 millisieverts which is high (32 x the exposure compared to CAC testing). A CT for the spine is 17 times the radiation dose of CAC testing.
CT Angiography (3 Dimensional) Versus Traditional Invasive Angiography (2 Dimensional)
In a comparison of the two procedures there was a study done which showed if you need to have clarifying angiography for chest pain, a positive treadmill or other findings, the invasive angiogram resulted in 80% more invasive procedures, twice as much money spent, and more radiation with no better diagnostic value. There was no added value going to the invasive angiogram versus the CT angiogram. If you need to put in a stent then use the traditional 2 dimensional angiogram and go to the cath lab. If just for diagnostic purposes the CT angiogram would be of greater value with less expense and risk.
Coronary Calcium Classification Scoring – What Does it Mean?
0 plaque burden is the goal and about 1/2 of individuals tested have no calcification. A score of 100 is moderate plaque burden. A score of 400 is severe plaque burden but scores can go up into the 1000s.
Think of a calcium score as a lifetime picture of atherosclerosis. You could be stable with a high score if this was from the past and you had changed your lifestyle such as changing your diet, getting exercise and you did not get any more plaque. As of right now you usually don’t see coronary calcification regression. But no more progression is a good thing. You may have a stiff artery but with exercise and lifestyle it could be functioning better than it was, or, it could be progressing if the score continued to go up significantly.
Soft plaque can be reversed by statin drugs, a garlic extract and possibly by some diet approaches. Calcified plaque is like scar tissue and probably isn’t regressing any significant amount. The only way you can see regression of atherosclerosis is to do CT angiography which could show regression of soft plaque which could mean the artery is getting softer and it could have a bigger lumen. If the calcium score isn’t going up that is a good sign. But some patients may want CT angiography to show they are reversing their soft plaque.
Is the CAC Test Paid For?
Medicare in most states will pay for the CAC testing if there are more three or more risk factors: high blood pressure, high cholesterol, family history, history of smoking and low HDL cholesterol. Most private insurances won’t pay for the test.
How Significant is Blood Cholesterol in the Atherosclerotic Process and Plaque Deposition?
LDL cholesterol is a significant player in creating these lipid cores. Triglycerides play a significant role as well. Triglycerides may play a role in inflammation and metabolic syndrome and this inflammation may increase the enzymes myeloperoxidase and LpPla2. Dr. Budoff thinks LDL cholesterol is a very bad player and triglycerides a somewhat bad player in the atherosclerotic process. Total cholesterol is not of value to assess. A naturally high HDL is protective but raising it with therapies has not been proven to be of benefit and remains to be proven. Dr. Budoff believes the number of LDL particles is significant. Like more cars on the freeway is bad, but the size of the LDL particles isn’t as important (i.e. it’s the number of cars not the size of the cars that is important for overall traffic burden)
Does the Benefit of Statins Outweigh the Risk?
Dr. Budoff believes the side effects to statin drugs is small, maybe 5-8% but the good news is they are reversible, side effects. The other point is that the evidence is clear that those who take statins live longer. They have reduced mortality. So he likes his patients to think they will be in the 92% plus of individuals who will benefit from statins. In patients with statin related side effects such as myalgias he will recommend CoQ10 but he has only seen some improvement in symptoms but not always. These side effects are believed to be due to statins effects on lowering CoQ10 levels thereby reducing mitochondrial energy production in the muscle cell or other cells.
Integrative physicians, he believes, feel they may be able to extend mortality in heart disease patients in other ways than using statins so they are more cautious with their use of statins.
Dr. Budoff’s A,B,Cs of Preventing Heart Attacks and Established Coronary Artery Disease
A – Aspirin – 81 mg low dose
B – Blood pressure control – lowering
C – Cholesterol lowering
D – Diet – Mediterranean style diet with fish consumption. Different diets for different scenarios weight reduction, diabetes control, etc.
E – Exercise is very important. It does everything. Reduces diabetes risk. Reduces blood sugar and improves glycemic control. It reduces cholesterol and improves HDL cholesterol. Lowers blood pressure. People live longer who are exercisers.
F – Fish consumption or fish oil (a study of a more concentrated EPA only supplement (Vascepa) – 980 mg of EPA per 1000 mg capsule. 4 grams daily of Vascepa in The REDUCE-IT (Reduction of Cardiovascular Events Outcomes) Trial he believes will show benefit). In the United States we are very poor at eating fish so supplementation may be the best way to go. G – Maybe garlic will be of benefit. It is part of the Mediterranean diet He has shown results in a trial of aged garlic extract in reversing soft plaque.
What Is The Price Range for the CAC Testing?
It should be below $150 per test. The Diagnostic and Wellness Center charges $129. A 64 slice scanner is minimum that should be used to get the best picture. Less than that and the machine is probably greater than 10 years old. The scanner at the Diagnostic and Wellness Center is a 256 slice scanner (~$1,000,000,000 machine). The picture can be read by a technologist. The equipment is more important than the expertise in reading the CAC scan.
Matthew J. Budoff, M.D. is a Professor of Medicine, David Geffen School of Medicine at UCLA; he is Director, Cardiac CT and Director, Fellowship Program, Division of Cardiology; Director of the Diagnostic and Wellness Center at Harbor-UCLA Medical Center, 1124 W. Carson Street, RB-2, Torrance, California 90502, email: Budoff@ucla.edu. Office (310) 222-4107; FAX (310) 787-0448; (310) 222-5101; CT Laboratory (310) 222-2773
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