The skeptical cardiologist has been utilizing coronary artery calcium (CAC) scans to help decide which patients are at high risk for heart attacks, and sudden cardiac death for the last decade. As I first described in 2014, (see here) those with higher than expected calcium scores warrant more aggressive treatment and those with lower scores less aggrressive treatment.
Although , as I have discussed previously, CAC is not the “mammography of the heart” it is incredibly helpful in sorting out personalized cardiovascular risk. We use standard risk factors like lipids, smoking, age, gender and diabetes to stratify individuals according to their 10 year risk of atherosclerotic cardiovascular disease (ASCVD) but many apparent low risk individuals (often due to inherited familial risk) drop dead from ASCVD and many apparent high risk individuals don’t need statin therapy.
Previously, major guidelines from organizations like the AHA and the ACC did not recommend CAC testing to guide decision-making in this area. Consequently, CMS and major insurers have not covered CAC testing. When my patients get a CAC scan they pay 125$ out of their pocket.. For the affluent and pro-active this is not an obstacle, however those struggling financially often balk at the cost.
I was, therefore, 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.
I don’t agree totally with this use of CAC but it is a step forward. For example, how I approach a patient with CAC of 1-99 depends very much on what percentile the patient is at. A score of 10 in a 40 year old indicates marked premature build up of atherosclerotic plaque but in a 70 year old man it indicates they are at much lower risk than predicted by standard risk factors. The first individual we would likely recommend statin therapy and very aggressive lifestyle changes whereas the second man we could discuss taking off statins.
Neil Stone, MD, one of the authors of the guidelines was quoted as saying that the imaging technique is “the best tiebreaker we have now” when the risk-benefit balance is uncertain.
“Most should get a statin, but there are people who say, ‘I’ve got to know more, I want to personalize this decision to the point of knowing whether I really, really need it.’ … There are a number of people who want to be certain about where they stand on the risk continuum and that’s how we want to use it,”
Indeed, I’ve written quite a bit about my approach to helping patients “get off the fence” on whether or not to take a statin drug.
Full title of these new guidelines includes an alphabet soup of organization acronyms
2018 AHA/ACC/AACVPR/AAPA/ABC/ACPM/ADA/AGS/APhA/ASPC/NLA/PCNA Guideline on the Management of Blood Cholesterol
N.B. For your reading pleasure I’ve copied the section in the new guidelines that discusses in detail coronary artery calcium.
Two interesting sentences which I’ll need to discuss some other time
-When the CAC score is zero, some investigators favor remeasurement of CAC after 5 to 10 years
–CAC scans should be ordered by a clinician who is fully versed in the pros and cons of diagnostic radiology.
–In MESA (Multi-Ethnic Study of Atherosclerosis), CAC scanning delivered 0.74 to l.27 mSv of radiation, which is similar to the dose of a clinical mammogram
-188.8.131.52. Coronary Artery Calcium
Substantial advances in estimation of risk with CAC scoring have been made in the past 5 years. One purpose of CAC scoring is to reclassify risk identification of patients who will potentially benefit from statin therapy. This is especially useful when the clinician and patient are uncertain whether to start a statin. Indeed, the most important recent observation has been the finding that a CAC score of zero indicates a low ASCVD risk for the subsequent 10 years (S184.108.40.206-1–S220.127.116.11-8). Thus, measurement of CAC potentially allows a clinician to withhold statin therapy in patients showing zero CAC. There are exceptions. For example, CAC scores of zero in persistent cigarette smokers, patients with diabetes mellitus, those with a strong family history of ASCVD, and possibly chronic inflammatory conditions such as HIV, may still be associated with substantial 10-year risk (S18.104.22.168-9–S22.214.171.124-12). Nevertheless, a sizable portion of middle-aged and older patients have zero CAC, which may allow withholding of statin therapy in those intermediate risk patients who would otherwise have a high enough risk according to the PCE to receive statin therapy (Figure 2). Most patients with CAC scores ≥100 Agatston units have a 10-year risk of ASCVD≥7.5%, a widely accepted threshold for initiation of statin therapy (S126.96.36.199-13). With increasing age, 10- year risk accompanying CAC scores of 1 to 99 rises, usually crossing the 7.5% threshold in later middle age (S188.8.131.52-13). When the CAC score is zero, some investigators favor remeasurement of CAC after 5 to 10 years (S184.108.40.206-14–S220.127.116.11-16). CAC measurement has no utility in patients already treated with statins. Statins are associated with slower progression of overall coronary atherosclerosis volume and reduction of high-risk plaque features, yet statins increase the CAC score (S18.104.22.168-17). A prospective randomized study of CAC scoring showed improved risk factor modification without an increase in downstream medical testing or cost (S22.214.171.124-18). In MESA (Multi-Ethnic Study of Atherosclerosis), CAC scanning delivered 0.74 to l.27 mSv of radiation, which is similar to the dose of a clinical mammogram (S126.96.36.199- 19). CAC scans should be ordered by a clinician who is fully versed in the pros and cons of diagnostic radiology.