Tag Archives: heart scan

The Ultimate Guide To The Coronary Artery Calcium Scan (Score) Circa 2019

The skeptical cardiologist’s first post on coronary artery calcium (CAC) scan was posted in 2014 and had the wordy title “Searching for Subclinical Atherosclerosis: Coronary Calcium Score-How Old Is My Heart?”

This post still serves as a good introduction to the test (rationale, procedure, risks) but in the 5 years since it was published there has been a substantial body of data published on CAC and in 2018 it was embraced by major organizations.

Overall, I’ve written 20 posts in which CAC plays a predominant role since then and I feels it’s time to put the most important changes and concepts  in one spot.


Detection Of Subclinical Atherosclerosis: What’s Your Risk of Dropping Dead?

First, the rationale for using CAC (also known as a coronary calcium score or heart scan) is detection of “subclinical atherosclerosis”, a non-catchy but hugely important process which I describe in an early post on who should take aspirin to prevent heart attack or stroke:

We have the tools available to look for atherosclerotic plaques before they rupture and cause heart attacks or stroke. Ultrasound screening of the carotid artery, as I discussed here, is one such tool: vascular screening is an accurate, harmless and painless way to assess for subclinical atherosclerosis.

In my practice, the answer to the question of who should or should not take aspirin is based on whether my patient has or does not have significant atherosclerosis. If they have had a clinical event due to atherosclerotic cardiovascular disease (stroke, heart attack, coronary stent, coronary bypass surgery, documented blocked arteries to the legs) I recommend they take one 81 milligram (baby) uncoated aspirin daily. If they have not had a clinical event but I have documented by either

  • vascular screening (significant carotid plaque)
  • coronary calcium score (high score (cut-off is debatable, more on this in a subsequent post)
  • Incidentally discovered plaque in the aorta or peripheral arteries (found by CT or ultrasound done for other reasons)

then I recommend a daily baby aspirin (assuming no high risk of bleeding).


Help In Deciding Who Needs Aggressive Treatment

Second, CAC is an outstanding tool for further refining 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 identifies those who do or don’t need statins.


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, 0.5 mSV) I concluded that CAC was not “the mammography of the heart” as the documentary proclaims.

What We Can Learn From Donald Trump’s CAC?

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 mininum 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 guidelines Take A Giant Step Forward

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 risk 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.

A Few Final Points On CAC

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 few 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.)

coronary calcium scan with post-processing on a 45 year old white male with very strong history of premature heart attacks in mother and father. The pink indicates the bony structures of the spine (bottom) and the sternum (top). Extensive calcium in the LAD coronary artery is highlighted in yellow and in the circumflex coronary artery in ?teal. His score was 201, higher than 99% of white male his age.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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 were 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. With these new studies and the new ACC/AHA guideline recommendations if they are age 40-75 years there is ample support for making CAC a part of such 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.

The Importance of Proactivity

In “The MESA App-Estimating Your Risk of Cardiovascular Disease With And Without Coronary Calcium Score” I recently wrote that:

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.

There are many other questions to answer with regard to CAC-should they be repeated?, how do statins influence the score?, is there information in the scan beyond just the score that is important? Is a scan helpful after a normal stress test?

I’ve touched on some of these in the past, including the really tough  question “Should All Patients With A High Coronary Calcium Score Undergo Stress Testing?

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.

I don’t want to wait a decade to start aggressively identifying who of my patients is at high risk for sudden death. You only get one chance to stop a death.

Apothanasically Yours,

-ACP


 

Is Coronary Calcium Scanning the Mammography of the Heart?

If you have watched The Widowmaker as suggested by the skeptical cardiologist you have likely been convinced that the developers and promoters of coronary artery calcium (CAC) scans, for the early detection of heart disease, are true heroes in the cardiology world.

These members of the “calcium club” are portrayed as unbiased self-less promoters of the prevention of heart attacks and sudden death, fighting an uphill battle against the evil procedure and money-driven forces who push coronary stents-greedy interventional cardiologists and the device, hospital and insurance industries.

A constant theme in the documentary is that CAC scanning should be to the heart what mammography is to the breast. It should be done on all patients over a certain age and should be covered by insurance.

As a non-invasive cardiologist with a strong interest in prevention, I am definitely a strong proponent of CAC scans in the right population. As the skeptical cardiologist, however, I find flaws with the mammography comparison.

Let’s review some of the established science regarding CAC scans.

What Is A CAC Scan?

coronary calcium
Coronary calcium scan from a 52 year old man I was seeing for palpitations. He had had an equivocal stress test but had a strong family history of CAD. Standard risk factors were unremarkable. As shown here, he has very extensive calcium in his coronary arteries. The left anterior descending (LAD) has lots of calcium (CA, indicated by arrows). His total score was 1798 which is at the 99th percentile for caucasian men his age. This means that his score is higher than 99% of caucasian men. Such a high score for age puts him in an extremely high risk category of heart attack and death.

The CAC scan utilizes computed tomography (CT)  X-rays, without the need for intravenous contrast, to generate a three-dimensional picture of the heart. Because calcium is very apparent on CT scans, and because we can visualize the arteries on the surface of the heart that supply blood to the heart (the coronary arteries), the CAC scan can detect and quantify calcium in the coronary arteries with great accuracy and reproducibility.

A preventive cardiologist, Dr. Arthur Agatson, who is interviewed in the film (and who is also the creator of the South Beach Diet, a low carbohydrate, high fat diet), developed a method for counting up the amount of calcium in the coronary arteries (the Agatson or calcium score).

Calcium only develops in the coronary arteries when there is atherosclerotic plaque. The more plaque in the arteries, the more calcium.

What Is The Risk Of  A High CAC Score

Multiple observational studies have shown that a high versus low calcium score is indicative of high risk for heart attack and death.

For example, a large study published in 2008 (the MESA study), followed 6,814 individuals for 3.8 years. Compared with patients with a CAC score of 0, patients with a CAC score of 101-300 had a 7.7 fold increase risk of a coronary event (heart attack). CAC score of >300 conferred almost a tenfold increase risk.

Screen Shot 2015-09-06 at 8.32.02 AMBased on data from 5 large studies and almost 15,000 patients, we can put patients with CAC score in very low to high risk categories for cardiac events over the next 10 years.

What Is The Value Of A Zero Calcium Score?

Just as important as identifying patients with advanced or premature atherosclerosis who should be getting intensive therapy  for prevention of cardiac events, is identifying those patients who may not warrant therapy.

A CAC score of zero puts a patient in an extremely low risk category.  A recent study, with the provocative title of:

A 15-Year Warranty Period for Asymptomatic Individuals Without Coronary Artery Calcium

…demonstrated that a zero calcium score confers this low risk of cardiac events for up to 15 years.

Thus, many patients, who are considered intermediate risk based on standard risk factors, do not have significant plaque by CAC score and may not need otherwise indicated statin therapy.

Mammography

The comparison of mammography to CAC scanning is appropriate in that both have created considerable controversy and are at the epicenter of discussions on the value of mass screenings in the prevention of life-threatening disease.

In contrast to CAC, mammography has been widely accepted and promoted by most professional organizations. In recent years, however, the value of mammography for all women over the age of 40 has been questioned.

In 1980, a randomized controlled trial of screening mammography and physical examination of breasts in 89, 835 women, aged 40 to 59, was initiated in Canada. It was called the Canadian National Breast Screening Study.

The findings published last year were:

Annual mammography in women aged 40-59 does not reduce mortality from breast cancer beyond that of physical examination or usual care when adjuvant therapy for breast cancer is freely available. Overall, 22% (106/484) of screen detected invasive breast cancers were over-diagnosed, representing one over-diagnosed breast cancer for every 424 women who received mammography screening in the trial.

Recently, the Swedish Medical Board recommended that all mammography screening be phased out in that country.

The US preventive services task force draft guidelines, updated earlier this year, will recommend screening for women aged 50-74 but not in those aged 40-49 years.

Downsides of breast cancer mammography screening include:

-Over-diagnosis: finding and treating breast cancer that would not have been a threat to the patient.

-False positives: the test identifies a possible cancer which is not subsequently confirmed. False positives lead to breast biopsies, which are not needed and often cause needless anxiety and stress.

-Radiation exposure.

Is CAC Screening The Cardiac Equivalent Of Mammography?

CAC scans differ fundamentally from mammography because atherosclerosis is a continuous and diffuse arterial process, whereas breast cancer is (most often) localized, and either present or not.

The development of atherosclerosis starts with fatty streaks in multiple arterial beds fairly early in life, followed by progressive plaque development with progressive build up of calcium in the plaques.

Thus, the CAC score ranges continuously from zero up to several thousand.

The calcium score is not subject to false positives-if calcium is detected, atherosclerotic plaque is present.

A mammogram is either abnormal, suggesting cancer and requiring a biopsy, or it is normal. There is no continuous grading of risk.

The second fundamental difference in the two disease processes is that atherosclerosis can kill suddenly without warning.

As pointed out in numerous examples in The Widowmaker, an individual can seem fit and hearty one minute, and be dead the next, from a heart attack caused by a lethal abnormal rhythm.

Breast cancer deaths on the other hand, occur slowly after diagnosis, and are generally predictable.

Nuclear Stress Tests are the Mammography of the Heart

If we are looking for a cardiac test that has characteristics similar to mammography, the nuclear stress test is much closer than CAC.

With a nuclear stress test we are using a radio tracer injected intravenously, which subsequently traverses the coronary arteries into the heart muscle. Subsequent imaging of the photons emitted by the radio tracer allows assessment of the status of blood flow down the coronary arteries.

The test is designed to identify coronary arteries with flow limiting blockages (usually >70% blocked), caused by atherosclerotic plaques. Such blockages are more likely to be causing symptoms and therefore more likely to require treatment with coronary stents or bypass surgery.

Like mammography, then, nuclear stress tests are either abnormal or normal, and when abnormal they can be falsely abnormal.

Nuclear stress tests have a very high incidence of false positives. These false positives result in invasive catheterization procedures to more directly image the arteries, and may result in inappropriate coronary stenting or bypass procedures with associated risks.

It is because of the high risk of false positives and attendant harm that in the last decade, all cardiac societies recommend against the routine use of stress testing in asymptomatic patients.

As pointed out in the Widowmaker, there is no data which suggest that stress testing improves outcomes for cardiac patients.

Stress tests by design tell us nothing about the noncritical build up of atherosclerotic plaque. You can have a normal stress test and have a huge burden of plaque in your arteries.

It is this silent build up of atherosclerosis, with sudden rupture of plaque, which results in sudden death in most cardiac patients.

What Is The Breast Cancer Equivalent Of CAC?

A CAC of the breast would identify abnormal cells as soon as they began on the presumably multi-year road to becoming a full flown cancer.

To be fully equivalent to the CAC, the breast CAC would have to have a proven treatment that could be instituted once a certain stage of cell transformation had been reached.

For atherosclerosis, that treatment is statin drugs, which are recommended for those with high risk CAC scores.

For breast cancer, the treatment of choice is mastectomy.

 Would Widespread Institution of CAC Screening Save Millions of Lives?

For mammograms based on a review of all the evidence, the US PTF concluded:

Over a 10-year period, screening 10,000 women ages 50 to 59 years will result in 8 (95% confidence interval [CI], 2 to 17) fewer breast cancer deaths, and screening 10,000 women ages 60 to 69 years will result in 21 (95% CI, 11 to 32) fewer deaths.

To scientifically determine how many lives are saved by CAC screening, we would need an extremely large randomized controlled trial lasting for at least 6 years.

Individuals with low or intermediate risk from standard risk factors for atherosclerosis would receive a standard approach to management or would undergo CAC screening with treatment determined by calcium score.

Such trials have been proposed but to date have not been funded by the NIH thus we may not have a definite answer for a long time.

Should CAC Scans Be Covered Like Mammography?

I am very conflicted on this question.

On one hand I do believe that appropriate use of CAC scans prevents heart attacks and sudden death. How many, remains to be seen. As we saw for mammography, only large scale randomized trials will tell us for sure who will benefit and how much.

On the other hand, I can see potential for abuse, and in the wrong hands, excessive downstream invasive testing, which will minimize the benefits of early detection.

If CAC scans are covered by insurance and used widely, they could become a method for unscrupulous cardiology centers and doctors to proceed to unnecessary testing that would ultimately increase the amount of inappropriate coronary stenting.

Indeed, it is quite ironic that the major theme of The Widowmaker, that of the medical-industrial stent complex suppressing CAC scan usage, is quite illogical, for widespread, injudicious use of CAC scanning would be a boon for stent inserters and makers.

The inappropriate use of CAC scan information is limited currently because most of the doctors ordering them are primarily interested in prevention, not in generating more testing and procedures.

The other limit on its use is cost. For 99% of my patients the $125 for a CAC scan at my hospital is not a limiting factor.

On the other hand, in a less affluent population, this would be a large and limiting expense; the poor would be getting a lesser standard of care.

The cases of patients in The Widowmaker who feel like a CAC scan saved their lives are very similar to those of breast cancer patients who feel mammography saved theirs.

These patients often become passionate advocates for a specific test based on their own experience. The Widowmaker, in fact, was funded by David Bobbett, an Irish millionaire who discovered that he had an extremely high calcium score and now feels like everyone should get the test.

Bobbett is convinced that the test saved his life, but all anecdotal patient stories about CAC scans “saving their life” have to be taken with a grain of salt.

After this (far too long) discussion I have to conclude that although they share many features, CAC scans are not the mammography of the heart.

uncharacteristically verbosely yours,

-ACP

Searching for Subclinical Atherosclerosis: Coronary Calcium Score-How Old Is My Heart?

Heart attacks and most sudden cases of sudden death are due to rupture of atherosclerotic plaques. Thus, it makes sense to seek out  such plaques, a process I call searching for subclinical atherosclerosis. I’ve talked about using high frequency ultrasound of the carotid arteries to the brain to look for plaque and for carotid IMT in earlier posts here and here.

There is a third method that looks directly at the coronary arteries, which supply blood to the heart.  It is variously called a heart scan, coronary calcium score, or cardioscan, and it is more widely utilized amongst physicians who are serious about preventing cardiovascular disease.

This technique utilizes the ionizing radiation inherent in X-rays to perform a CT examination of the chest. It does not require injection of any dye or the puncture of any arteries; thus, it is considered noninvasive and has no risk or pain associated with it.

When atherosclerosis first begins to form in the arteries, it generally takes the form of “soft” plaques. Soft plaques are initially full of lipids, but after a period of time, the plaques undergo change: calcium begins to deposit into this plaque.

There is a direct relationct_calciumship between coronary artery calcium (CAC) and the amount of atherosclerotic plaque in the coronary arteries.

CT scans are very accurate in identifying small amounts of calcium in the soft tissue of the body. Calcium score tests essentially look for blobs of calcium that are felt to be within the coronary arteries, count up the intensity and distribution of them, and calculate a total score that reflects the entire amount of calcium in the coronary arteries.

A large body of scientific literature has documented that higher calcium scores are associated with higher risk of significantly blocked coronary arteries and of heart attack.

You can read the NHLBI clinic’s info for patients here on the test.

How Is The Calcium Score Used To Help Patients?

The calcium score can be utilized (in a manner similar to the carotid IMT and plaque) to help determine whether a given individual has more advanced atherosclerosis than we would predict based on their risk factor profile. A score of zero is consistent with a very low risk of significantly blocked arteries and confers an excellent prognosis. On the other hand, scores of >400 indicate extensive atherosclerotic plaque burde , high risk of heart attack, and high likelihood of a significantly blocked coronary artery.

The calcium score (similar to the carotid IMT) increases with age and is higher in males versus females at any given age. We have very good data on age and gender normals. The average 50-59 year old woman has a zero score, whereas a man in that age range has a score of 30. The average man has developed some CAC by the fourth decade of life whereas the average woman doesn’t develop some until the sixth decade. More advanced CAC for age and gender is a poor prognostic sign. You can plug your own age, gender, race and CAC score into a calculator on the MESA (Multi-ethnic Study of Atherosclerosis) website here.

2013 ACC/AHA Guideline on the Assessment of Cardiovascular Risk says the following

 If, after quantitative risk assessment, a risk based treatment decision is uncertain, assessment of 1 or more of the following—family history, hs-CRP, CAC score, or ABI—may be considered to inform treatment decision making

This guideline recommended utilizing a  CAC score of >300 Agatson Units or >75th percentile for age, gender and ethnicity as a cut-off.

CAC Score Identifies Those At Very High  Risk

A forty-something year old man came to see me for palpitations. He had a stress echo which was normal except for the development of frequent PVCs and a brief run of non sustained ventricular tachycardia.  His risk factor profile was not particularly bad: no diabetes, hypertension, or cigarette smoking and an average lipid profile. When I calculated his 10 year risk of ASCVD using my iPhone app it came out at 7%: below the level at which statin treatment would be recommended.  Because his father had a coronary stent in his fifties (this does not qualify as a family history of heart disease according to the new guideline, by the way)  I recommended he get a CAC test done.

His CAC score came back markedly elevated, almost 1000.  .  A subsequent cardiac catheterization demonstrated a very high-grade coronary blockage iwhich was subsequently stented. I started him on high intensity statin therapy and he has done well.

CAC score identifies Those At Very Low Risk

Many individuals with high cholesterol values do not develop atherosclerosis.  A zero CAC score in a male over 50 or a woman over 65 (or non-zero CAC score that is <25th percentile for age, gender, ethnicity) indicates that they are not developing atherosclerosis and makes it less likely that they will benefit from statin therapy to lower cholesterol.

Some Caveats About CAC score testing

-Like carotid vascular screening, there is no reason to get a CAC test if you already have had problems related to blocked coronary arteries such as a heart attack or coronary stents or coronary bypass surgery.

-CAC score testing is not covered by insurance (except in Texas) and costs somewhere between $125 and $300 out of pocket.

-The CT scan leads to a small amount of radiation exposure-approximately 1 – 2 milliseiverts of radiation (mSv). To puts things in perspective, the annual radiation dose we receive from natural sources is around 3 mSV per year.

Some of the other approximate radiation doses for tests commonly used in medicine are:

Chest X-ray ( )            0.1 mSV
Routine CT chest:  10 mSV
CT abdomen: 10 mSV
Nuclear stress test: 10 to 20 mSV