The Skeptical Cardiologist's Guide To The Coronary Artery Calcium Scan

A quick, accurate and simple test that better assesses your risk of heart attack

Preventive cardiologists have a wonderful tool for noninvasively identifying plaque (atherosclerosis) in the arteries to the heart: the coronary artery calcium (CAC) scan.

Since 1/3 of Americans die from atherosclerotic cardiovascular disease (ASCVD, mostly heart attacks, and strokes) and dropping dead is often the first symptom of ASCVD, it is incredibly important to identify early, “subclinical” ASCVD (see here) and begin measures to reduce risk.

How early to begin that process is open to debate. The sudden death of the 41-year-old son of a patient of mine, reinforced to me how crucial it is to begin risk assessment and potential treatments as early as possible, especially in individuals with a strong family history of premature ASCVD.

We use standard risk factors like lipids, smoking, age, gender, and diabetes to stratify individuals according to their 10-year risk of heart attack and stroke (using this online risk calculator) but many apparent low-risk individuals (often due to inherited familial risk) drop dead from ASCVD and many apparent high-risk individuals have no subclinical ASCVD and don’t need preventive therapy.

I’ve been utilizing CAC (also termed heart scan, coronary calcium score, or cardioscan) to help assess my patient’s risk of ASCVD for years although the procedure is not covered by insurance and until recently was not strongly endorsed by major guidelines. 

“Searching for Subclinical Atherosclerosis: Coronary Calcium Score-How Old Is My Heart?” serves as a good introduction to the test (rationale, procedure, risks) but in the 9 years since the skeptical cardiologist wrote that article there has been a substantial body of data published on CAC and in 2018 it was embraced by ACC/AHA guidelines.

Above are unprocessed (left) and processed CAC images. The yellow smudge marks calcium plaque in the LAD coronary artery.

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For those who prefer their information from videos check out this one….A simple, inexpensive test can assess your risk of early heart disease. Here's how.

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THE CAC CAN HELP IN DECIDING WHO NEEDS MORE AGGRESSIVE TREATMENT

The CAC is an outstanding tool for further refining the risk of heart attack and stroke and helping better determine who needs to take statins or undergo aggressive lifestyle reduction, something I described in detail in my post “Should All Men Over Sixty Take a Statin Drug”.

The updated AHA/ACC Cardiovascular Prevention Guidelines came out in 2013.
After working with them for 9 months and using the iPhone app to calculate my patients’ 10 year risk of atherosclerotic cardiovascular disease (ASCVD, primarily heart attacks and strokes) it has become clear to me that the new guidelines will recommend statin therapy to almost all males over the age of 60 and females over the age of 70.
As critics have pointed out, this immediately adds about 10 million individuals to the 40 million or so who are currently taking statins.
By identifying subclinical atherosclerosis, CAC scoring more precisely identifies those who do or don’t need statins.

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This is particularly important for patients who have many reservations about statins or who are “on the fence” about taking them when standard risk factor calculations suggest they would benefit.

THE WIDOWMAKER

In 2015 I wrote about a documentary entitled “The Widowmaker” (see here and here) which is about the treatment and prevention  of coronary artery disease and what we can do about the large number of people who drop dead from heart attacks; some 4 million in the last 30 years:

The documentary, as all medical documentaries tend to do, simplifies, dumbs down and hyperbolizes a very important medical condition. Despite that it makes some really important points and I’m going to recommend it to all my patients.
At the very least it gets people thinking about their risk of dying from heart disease which remains the #1 killer of men and women in the United States.
Perhaps it will have more patients question the value of stents outside the setting of an acute heart attack. This is a good thing.
Perhaps it will stimulate individuals to be more proactive about their risk of heart attack. This is a good thing.

Although CAC has some similarities to mammography (both utilize low-dose radiation and both are screening modalities) I concluded that CAC was not “the mammography of the heart” as the documentary proclaims.

WHAT CAN WE LEARN FROM DONALD TRUMP’S CAC SCORE

In 2018 I noted that “Donald Trump Has Moderate Coronary Plaque: This Is Normal For His Age And We Already Knew It.”

In October, 2016 the skeptical cardiologist predicted that Donald Trump’s coronary calcium score, if remeasured, would be >100 .  At that time I pointed out that this score is consistent with moderate coronary plaque build up and implies a moderate risk of heart attack and stroke.
Trumps’ score gave him a seven-fold increase risk of a cardiovascular event in comparison to Hilary Clinton (who had a zero coronary calcium score) .
Yesterday it was revealed by the White House doctor , Ronny Jackson, that Trump’s repeat score  was 133.
I was able to predict this score because we knew that Trump’s coronary calcium was 98 in 2013 and that on average calcium scores increase by about 10% per year.

What is most notable about the Trump CAC incident is that Trump, like all recent presidents and all astronauts underwent the screening. If the test is routine for presidents why is it not routine for Mr and Mrs Joe Q Public?
At a minimum, we should consider what is recommended for aircrew to the general public:

A three-phased approach to coronary artery disease (CAD) risk assessment is recommended, beginning with initial risk-stratification using a population-appropriate risk calculator and resting ECG. For aircrew identified as being at increased risk, enhanced screening is recommended by means of Coronary Artery Calcium Score alone or combined with a CT coronary angiography investigation.

THE 2018 ACC/AHA GUIDELINES ENDORSED CAC

In late 2018 I noted that CAC had been embraced by major guidelines:

I was very pleased to read that the newly updated AHA/ACC lipid guidelines (full PDF available here) emphasize the use of CAC for decision-making in intermediate ris.k patients
 
For those patients aged 40-75 without known ASCVD whose 10 year risk of stroke and heart attack is between 7.5% and 20% (intermediate, see here on using risk estimator) the guidelines recommend “consider measuring CAC”.
If the score is zero, for most consider no statin. If score >100 and/or >75th percentile, statin therapy should be started.

But what about the individual who has a strong family history of premature CAD and is age say 35 or 39 years of age? Do we ignore advanced risk assessment? Very few individuals die in their 30s from ASCVD but I have a number of patients who suffered heart attacks in their forties.

THE IMPORTANCE OF BEING PROACTIVE WITH YOUR CARDIOVASCULAR HEALTH

First, it’s never too early to start thinking about your risk of cardiovascular disease. I have been using CAC more frequently in the last five years in individuals <40 years with a strong family of early sudden death or heart attack and often we find very abnormal values (see here for my discussion on CAC in the youngish and here for a combined imaging and biomarker approach.)

In addition, the earlier we can start risk modification the better as the process begins very early in life and accumulates over time.

The Coronary Artery Risk Development in Young Adults (CARDIA) Study published in 2017 has demonstrated the early development of a nonzero CAC score in the youngish and the predictive value of the high CAC score for mid-life ASCVD events.  It was a prospective community-based study that recruited 5115 black and white participants aged 18 to 30 years from March 25, 1985, to June 7, 1986. The cohort has been under surveillance for 30 years, with CAC measured 15 (n = 3043), 20 (n = 3141), and 25 (n = 3189) years after recruitment. The mean follow-up period for incident events was 12.5 years,
The conclusions:

Any CAC in early adult life, even in those with very low scores, indicates significant risk of having and possibly dying of a myocardial infarction during the next decade beyond standard risk factors and identifies an individual at particularly elevated risk for coronary heart disease for whom aggressive prevention is likely warranted.

If heart disease runs in your family or you have any of the “risk-enhancing” factors listed above, consider a CAC, nontraditional lipid/biomarkers, or vascular screening to better determine where you stand and what you can do about it.

Included in my discussions with my patients with premature ASCVD is a strong recommendation to encourage their brothers, sisters, and children to undergo a thoughtful assessment for ASCVD risk.

There is ample support for making CAC a part of such an assessment.

Hopefully, very soon, CMS and the health insurance companies will begin reimbursement for CAC. As it currently stands, however, the 125$ you will spend for the test at my hospital is money well spent.

If you want to be proactive about the cardiovascular health of yourself or a loved one, download the MESA app and evaluate your risk.  Ask your doctor if a CACS will help refine that risk further.

MORE QUESTIONS AND ANSWERS ON CAC

There are many other questions to answer with regard to CAC:

• Should they be repeated? If non-zero, I say no. If zero, I say yes, in 2-4 years. (Findings from the MESAstudy (mean age 58 ± 9 years , 63% women, mean 10-year atherosclerotic cardiovascular disease risk 14 ± 13%) in patients with an initial zero CAC showed that the prevalence of CAC >0 increased with time, from 11% at 2 years to 50% at 10 years. Using a testing yield of 25% (number needed to scan = 4 to detect CAC >0), the estimated time period to CAC conversion of low, intermediate, and high estimated risk men was 7, 4, and 3 years, respectively, and for women was 8, 5, and 3 years, respectively.)

• Do statins influence the score? Yes. CAC score may actually be higher on statins than if you were not. This is because calcium is taken up into plaques as they “heal” or progress from active/inflamed/likely to rupture to scarred and quiescent.

• Will I benefit from a CAC if I have had a coronary stent/ coronary bypass surgery or other clinical event due to advanced ASCVD? No. We are going to treat you aggressively no matter what the CAC shows in this situation.

• Is there information in the scan beyond just the score that is important? Yes. The standard method of quantifying CAC from non-contrast cardiac-gated computed tomography (CT) scans is the Agatston score. The Agatston method, which up-weights the area of calcified plaque for greater calcium density, assumes that both the area and density of calcified plaques are positively related to ASCVD events. However, MESA (Multi-Ethnic Study of Atherosclerosis) has shown that CAC density was inversely associated with incident CVD events.

• Is a scan helpful after a normal stress test? It can be because stress tests are designed to identify tightly blocked coronary arteries. You can have loads of atherosclerotic plaque lining your arteries and have a totally normal stress test.

• “Should All Patients With A High Coronary Calcium Score Undergo Stress Testing? I now believe the answer to this is no. If the patient has symptoms suggestive of angina or ischemia then stress testing or coronary CT angiography is appropriate.

• Doesn’t CAC scanning miss early, soft plaque that can be easily identified on a coronary CT angiogram (CCTA)? Yes, it does. The CCTA gives us a complete picture of the coronary arteries including soft and calcified plaque along with a good estimate of the degree of narrowing of the arteries. However, a CCTA does not work well for screening purposes because 1) It’s expensive (typically >$800 out of pocket cost versus around $100 for CAC) and 2) It uses much higher radiation doses (3-8 mSv versus 1 mSv for CAC and 3) IV contrast is needed.

Like most things in cardiology, we have a lot to learn about CAC. There are many more studies to perform. Many questions yet to be answered.

A study showing improved outcomes using CAC-guided therapy versus non-CAC-guided therapy would be nice. However, due to the long time and thousands of patients necessary it is unlikely we will have results within a decade.

We can blame a lot of heart disease on lifestyle: poor diets and lack of exercise are huge factors leading to obesity, diabetes, hypertension and hyperlipidemia, but in many patients I see who develop heart disease at an early age, lifestyle is not the issue, it is the genetic cards that they have been dealt.

Until we develop reliable genetic methods for identifying all those at high risk it makes sense to utilize methods such as vascular screening or coronary calcium to look for atherosclerosis in individuals with a family history of premature CAD.
The earlier we start looking, the earlier we can intervene and lower the slow and progressive build-up of atherosclerotic plaque in the arterial beds.

Given, that we have extremely safe and effective medications that can help individuals dramatically reduce their lifelong risk of heart attack it makes sense to look early and intervene accordingly.

I don’t want to wait a decade to start aggressively identifying who of my patients is at high risk for sudden death, heart attack or stroke.

Apothanasically Yours,
-ACP