Coronary Artery Calcium Score


Coronary Calcium Score

Calcium is a chemical element that is essential for living organisms.

Most of the calcium within the human body is found in teeth and bone. Small amount, about one percent of total body calcium, is dissolved in the blood.

Undissolved calcium is metallic and hard and is difficult to break or cut with a knife.

When we age, calcium deposits can be found in many parts of our bodies. Calcification of the walls of the arteries is common in people aged 65 and older. Calcification of the breasts is often seen in women after the age of 50.

So, to a certain extent calcification of arteries and internal organs can be regarded as a normal part of aging.

Due to their metallic nature and density, calcium deposits are easily detected by X-ray images. In the early days of cardiac imaging, doctors relied on detecting calcium, as it often was the only feature that stood out on radiographs of the heart.

If arterial calcification is abundant, the aorta and coronary arteries can be outlined on a plain radiographic image. Today these methods have been replaced by more sophisticated modern imaging techniques.

Coronary Artery Disease

The coronary arteries are important vessels that supply blood to the heart muscle. To be able to function normally, heart muscle cells need a continuous supply of blood, delivering important nutrients of which oxygen is most important.

Atherosclerosis, is a chronic inflammatory condition that may cause narrowing of arteries, and rupture of arterial plaques, resulting in blood clotting (thrombosis) and sudden disruption of blood flow. Due to several different reasons, the coronary arteries are very prone to atherosclerosis

If the supply of blood is disrupted, parts of the heart muscle may die, and will be replaced by scar tissue. This can compromise the ability of the heart to pump blood to the organs of the body.

The term acute heart attack (myocardial infarction) refers to a situation where there is sudden blockage (occlusion) of blood flow in a coronary artery.

In the early 1960’s several risk factors for atherosclerosis and coronary artery disease were defined. Since then it has been repeatedly documented that smoking, lipid disorders and high blood pressure are associated with increased risk. Other conditions that predispose to coronary artery disease are family history, insulin resistance, physical inactivity, mental stress and depression.

Identifying individuals at risk is very important in order to reduce the risk of coronary artery disease. Therefore, knowledge of risk factors and how to reduce their influence is of key importance.  The declining death rate from coronary disease seen for the last 35 years can to a large extent be explained by reductions in major risk factors such as blood cholesterol, blood pressure and smoking (1).

Atherosclerotic coronary heart disease is still the most common cause of death in the Western world. Thus far, our ability to screen for this disease has been limited.

Although the usefulness of screening is still debated, assessing the amount of calcium within the walls of the coronary arteries may provide important prognostic information

Coronary Artery Calcification

Although calcification of the coronary arteries can be regarded as an aging phenomenon, extensive calcification appears to reflect more intense atherosclerosis, higher risk of heart attack, and worse prognosis.

Coronary calcification can be seen in adolescents, although it usually starts later in life.

The calcification is composed of calcium phosphate which is similar to that in bone.

For a long while, arterial calcification was thought to be the result of a degenerative process, but recent evidence suggests a that a more active process is involved, possibly resulting from injury or inflammation within the vessel wall.

In June 2000, the American College of Cardiology (ACC) and American Heart Association (AHA) Consensus Panel wrote in the Journal of the American College of Cardiology: “Coronary calcium is part of the development of atherosclerosis; …it occurs exclusively in atherosclerotic arteries and is absent in the normal vessel wall.”

Coronary Artery Calcium Score

In the 1980’s US cardiologists lead by Dr. Arthur Agatston defined a method to assess the amount of coronary artery calcium by using electron beam computed tomography, otherwise known as ultra fast CT scan.

The density of calcium is assessed by the so-called Hounsfield scale which measures density in Hounsfield units. The weighed score multiplied by the area of the coronary calcification provides the calcium score, commonly termed the Agatson score

The amount of calcium within the walls of the coronary arteries, assessed by the Agatston score, appears to be a better predictor of risk than standard risk factors (2).

A recent study found that progression of coronary calcification, assessed by two scans in 2.5 years, was associate with increased risk of cardiovascular events during a follow-up of more then 7 years (3).

The presence and extent of coronary calcium is first and foremost a marker of the extent of atherosclerosis within the coronary arteries. Nonetheless, it is important to understand that the coronary calcium score does not necessarily reflect the severity of narrowing (the degree of stenosis). Still, a patient with high calcium score is more likely to have a significant narrowing of a coronary artery than a patient with low calcium score.

An individual without coronary artery calcification is very unlikely to have a severe narrowing of a coronary artery (4).

Although cardiovascular events can occur in patients with very low calcium scores, the incidence is very low.

Based on a number of studies, the following definitions are used to relate the coronary artery calcium score to the extent of atherosclerotic coronary artery disease:

  • Coronary calcium score 0: No identifiable disease
  • Coronary calcium score 1-99: Mild disease
  • Coronary calcium score 100-399: Moderate disease
  • Coronary calcium score > 400: Severe disease

When interpreting coronary artery calcium score it is very important to consider age and gender. For example 50% of white males aged 70 have a calcium score higher than 14,5 and 50%  of white females aged 70 have a calcium score above 13. There is a calculator available here that provides coronary calcium score distribution based on age, gender and ethnicity.

How Is Coronary Calcium Assessment Performed?

Coronary Calcium Score

To begin with, coronary calcium assessment with CT was made possible with the development of the electron-beam CT scanner in the late 1980’s. The speed of this machine was much higher than that of existing scanners. The high speed made it possible to “freeze” heart motion to allow measurements of calcium in the coronary arteries.

Lately, ultrafast spiral CT has been used to assess coronary calcium. This technique makes the scanning time very short. Often a scanning length of around 10 seconds is used.

The patient usually needs no specific preparation. Fasting is not necessary. As high heart rate may reduce imaging quality, patients are often asked to refrain from smoking and drinking coffee before the scan. Sometimes beta blockers are administered to slow heart rate.

Many experts have expressed concerns about the radiation involved with the CT scan. It has been estimated that there may be an increase in radiation-induced cancer risk with repeated procedures (5).

What to Do About Extensive Coronary Calcification?

There is no specific treatment available that lowers coronary calcium.

One randomized placebo controlled trial (6) did not find any significant benefit with atorvastatin (cholesterol lowering drug), vitamin C and vitamin E in patients with high coronary artery calcium score.

Although blood levels of cholesterol were reduced, there was no effect on progression of coronary calcium score. Atherosclerotic cardiovascular events were fewer in the drug treatment group compared with placebo, but the difference was not statistically significant. However, there was a greater treatment effect in a subgroup with coronary calcium scores above 400.

Treatment of individuals with high calcium scores should aim at reducing risk. This involves treating lipid disorders, high blood pressure and diabetes if present. Refraining from smoking is essential. Regular, moderate exercise is advised. Due to the overwhelming evidence of benefit in individuals with atherocslerotic heart disease, treatment with aspirin and statins is generally advised.

If extensive calcification is present, further evaluation may be needed. Stress test associated with nuclear and echocardiographic imaging techniques is often performed. Coronary catheterization with angiography of the coronary arteries may be indicated to assess the severity and extent of coronary narrowing.

Comments

  1. says

    I had one of these done last year, 49 years old, score was 37, so I guess that’s pretty good. I had it done for my own personal interest.

  2. Edith Nir says

    So which is it – should we use statins to lower risk (with score under 400) or will it not have an effect on the calcification progression???

    • Axel F Sigurdsson says

      @ Edith Nir

      There is no evidence thus far that statins will reduce the progression of coronary calcium.

      The rationale for their use is based on the assumption that individuals with high calcium scores have extensive atherosclerosis, and the fact that statins have been shown to improve outcome in patients with established atherosclerotic cardiovascular disease.

    • Axel F Sigurdsson says

      Thanks for the links Ted.

      I really enjoyed reading the review on K2. Its promising role for preventing or modulating vascular calcification is of great interest.

      The question whether the anti-inflammatory effects of vitamin K and vitamin D may be important when it comes to preventing vascular calcification is also of great interest. Both these nutrients appear relatively safe and they’re certainly not expensive.

  3. Jkart says

    It’s not clear what CT measuring of arterial calcification really means. Is it the measurement of the length of arterial vessel affected by calcification? Or is the measurement of arterial narrowing from calcification?

    If one has a score that puts them at the 50th percentile for their age/sex, then how frequent should CT technology be used to monitor the progression? Every year? Every 3 years? ???

    • Axel F Sigurdsson says

      @ Jkart

      Coronary calcium score reflects the total amount of calcium within the walls of the coronary arteries, taken together to provide a single number. It’s based on density and area.

      Coronary calcium score tells you nothing about arterial narrowing. One can have a high calcium score without any narrowing or blockages being present. However, a patient with high calcium score is more likely to have a significant narrowing affecting blood flow than a patient with low calcium score.

      Regarding your last question the only thing I can tell you is that nobody really knows how to use coronary calcium score in clinical practice. Whether, or how often progression should be monitored is still a matter of debate.

      • Jkart says

        Thanks for the clarifications. For whatever reason, it was in my mind that the calcium score was directly related to the level of vessel blockage.

  4. says

    Thanks for the post Axel. In our reports Volume130 is also reported an it is suggested that it be used to measure progression from year to year rather than AJ scores.

    There has been some debate regarding the essence of calcium scores and its ability to predict risk.

    Glad you posted because I wanted to discuss with you. Comments?

    Jeff

    • Axel F Sigurdsson says

      Thanks Jeff

      I think there are several things to discuss and many unresolved issues when it come to coronary artery calcium score (CACS).

      One thing worth mentioning is that CACS is probably not very useful as a diagnostic tool. By that I mean that if you have a patient with chest pain, breathlessness or other symptoms, you’ll have to use other methods such as exercise testing with or without nuclear or echocardiographic images and then, if positive,coronary angiography.

      I don’t think CACS is a useful screening tool for large parts of the population. In that respect, it’s probably not cost-effective. Radiation is involved and there are cheaper methods available.

      However, CACS may be helpful when assessing individuals at intermediate risk. There may be situations where you’re wondering whether to treat with statins or not. If there is extensive calcification, you might want to recommend statins while on the other hand, if there is no calcification, risk is low (even in the case of high LDL-cholesterol) and you might want to refrain from statin treatment.

      What’s your experience in Denver and among general practitioners in the US? Is CACS being used to assess risk?

      • says

        Axel,

        In the US insurance is not paying for CACS, this usually means that insurance concludes that it does not provide useful information. However, many pay out of pocket for the screen and I agree as you stated above there may be some usefulness.

        We do CIMT’s with limited doppler in our office as a competing technology. I am not sure itima thickness correlates with risk but I like to visualize plaque. I suppose that using these tools in the right context can be useful.

        Jeff

  5. John wagner says

    I suspect a calcium score will turn out to have a practice value other than measuring it like the length of a fuse on a time bomb, and having no treatment to stop this progression. If a person has a high score and angina/significant block, then surgical treatment might be more indicated, as compared to same person except low calcium score. This person might respond better to medical treatment, ie statins, etc. bottom line, use it to help decide surgical versus medical treatment of coronary disease.

    • Axel F Sigurdsson says

      John.

      That’s a hypothesis that is still to be tested.

      I don’t now of any evidence so far suggesting that calcium score is useful when deciding whether to go for surgery or medical therapy. Usually these decision are based on the number of arteries with significant narrowing (stenosis) assessed by coronary angiography, the localization of the narrowings and the extent of myocardial ischemia.

  6. Don A says

    I would appreciate any comments/advice from the experts on this blog. I am a 62y.o. male at 5’11’ and weigh 213 lbs after losing 20 lbs since Feb 2014 and have started exercising and cycling regularly since March of this year. I plan to lose another 20 lbs. I have mild asthma and take asmanex 220mcg
    2 puffs daily. BP is well within normal limits. In Sept. 2000 I had aCAC of 11. LMA: 0, LAD: 9,CFX: 0, RCA: 2. IN 2007 I had an angiogram due to a thallium stress showing a possible problem but cardiologist thought was false positive. Results of angiogram was RCA – mild diffuse disease , left main – no disease, lad proximal <30%, Mid < 30%, D1 no obstruction, Lcx – no obstruction. No treatment rendered. After blood workup my cardiologist put me on 20mg of lipitor. I have been on 20 mg lipitor since early 2008.
    Now for my concern, Sept 5th I had a stress echo. Negative findings except for showing pac on exercise. His concern was that the width of pvc ( recovery period ) was wider than usual. I am asymptomatic on 24 mile road bike trips and exercise. Sometimes on strenuous exercise take pulse and feel extra beats every 8 – 16 beats.
    The kicker here is that I had a repeat CAC score November, 2013. Cardiologist told me via email that it was significantly higher, but nothing to worry about and didn't give me the number. Recommended stress/echo which I took my time about. At office visit I asked for test result, what a shock. Total CAC score 1693. LM- 0, LAD- 1141, D1 – 37, CX – 27, RCA – 488, PDA – 0. This shook me to my core. I questioned my cardiologist who is well respected in NYC and he assured me not to be worried. Told me about studies showing Lipitor helps soft plaque become more stable by hardening it and this causes deposition of calcium causing higher score. I have searched internet for this phenomena and found nothing but came upon your blog.
    My cardiologist reiterated over and over not to worry but to be on safe side and not for elevated CAC score but for exercise induced pvc width referred me for a virtual angiogram ( cat of heart).
    Needless to say, I am extremely concerned about the CAC score which is virtually off the charts.
    Any recommendation/clarification you can give would be greatly appreciated

    • Axel F Sigurdsson says

      Don A.

      Some studies have suggested that there is an association between statin use and coronary artery calcification. Furthermore, there is no evidence that statin treatment halts the progression of coronary calcification.

      However, this does not mean that statins accelerate the progression of atherosclerosis. In fact, as your cardiologist suggested, calcification of plaques may indicate healing. In theory, a calcified plaque may be more stable and less likely to rupture than a non-calcified plaque.

      It is possible that there are different mechanisms behind coronary calcification and coronary artery narrowing. In one meta-analysis, coronary calcification was not affected by statin therapy although there was a consistent moderation of progression of coronary artery narrowing with statins.

Let me know what you think!