(This post was updated 12/26/2022)
The skeptical cardiologist has repeatedly laid out the case for utilizing coronary artery calcium score (CACS) to more precisely assess the risk of heart attack or stroke in youngish individuals.
Guidelines recommend the ACC/AHA ASCVD risk estimator tool (app available here) as the starting point for estimating an individual’s risk but if I have information on my patient’s CACS I use a superior tool called the MESA risk score calculator.
It is available online and through an app for Apple and Android (search in the app store on “MESA Risk Score” for the (free) download.)
The MESA tool allows you to easily calculate how the CACS affects you or your patient’s 10-year risk of heart attack or stroke (aka ASCVD.)
The Multi-Ethnic Study of Atherosclerosis (MESA) is a study of the characteristics of subclinical cardiovascular disease (disease detected non-invasively (with tests like CAC) before it has produced clinical signs and symptoms) and the risk factors that predict the progression to clinically overt cardiovascular disease or progression of the subclinical disease.
MESA researchers have been studying outcomes since 2000 in a diverse, population-based sample of 6,814 asymptomatic men and women aged 45-84. Approximately 38 percent of the recruited participants are white, 28 percent African-American, 22 percent Hispanic, and 12 percent Asian, predominantly of Chinese descent.
A wealth of publications (69 at last count) have come out of the MESA database with many of them informing our understanding of the value of CAC.
To use the MESA score you will need information on the following risk factors:
age, gender, race/ethnicity, diabetes (yes/no), current smoker (yes/no), total and HDL cholesterol, use of lipid-lowering medication (yes/no), systolic blood pressure (mmHg), use of anti-hypertensive medication (yes/no), any family history of a heart attack in a first-degree relative (parent/sibling/child) (yes/no), and a coronary artery calcium score (Agatston units).
In my experience, the CACS in many patients dramatically lowers or increases the estimated risk of cardiovascular events the patient faces.
In this example a 64-year-old man with no discernible risk factors has a CACS of 175
Using the standard risk factor calculation, the doctor and patient would be reassured the patient is at a low risk (<5%.)
However, the 10 year risk of a CHD event almost doubles from 4.7% to 7.6% when the CACS is added to the standard risk factors and moves into a range where we need much more aggressive risk factor modification to prevent
On the other hand if we enter in zero for this same patient the risk drops to a very low 1.9%.
It’s also instructive to adjust different variables. For example, if we change the family history of heart attack (parents, siblings, or children) from no to yes, this same patient’s risk jumps to 7.2% (2.6% with zero calcium score and to 10.4% with CACS 175.)
It can also be used to help modify risk-enhancing behaviors. For example if you click smoker instead of non-smoker the risk goes from 4.7% to 7.5%. Thus, you can tell your smoking patient that his risk is halved if he stops.
Discussions on the value of tighter BP control can also be informed by the calculator. For example, if our 64 year old’s systolic blood pressure was 160 his risk has increased to 6.8%.
How Does Your CACS Compare To Your Peers?
A separate calculator allows you to see exactly where your score stands in comparison to individuals with your same age, gender, and ethnicity
The Coronary Artery Calcium (CAC) Score Reference Values web tool will provide the estimated probability of non-zero calcium, and the 25th, 50th, 75th, and 90th percentiles of the calcium score distribution for a particular age, gender and race. Additionally, if an observed calcium score is entered the program will provide the estimated percentile for this particular score. These reference values are based on participants in the MESA study who were free of clinical cardiovascular disease and treated diabetes at baseline. These participants were between 45-84 years of age, and identified themselves as White, African-American, Hispanic, or Chinese. The current tool is thus applicable only for these four race/ethnicity categories and within this age range.
The calculator tells us that 75% of 64 year old white males have a non-zero CACS and that the average CACS is 61.
Unlike SAT scores or Echo Board scores you don’t want your CACS percentile status to be high.
Scores >75th percentile typically move you to a higher risk category,
Scores <25th percentile move you to a lower risk category, often with significant therapeutic implications (e.g. you likely don’t need cholesterol lowering medications.)
Scores between the 25th and 75th percentile typically don’t significantly change the risk calculation.
Exploring Gender Differences In CACS
If we change the gender from male to female on our 64 year old the risk drops considerably from 4.7% down to 3.3%. This graph demonstrates that over 20% of women between the ages of 75 and 84 years will have zero calcium scores.
The graph for men in that same range shows that only around 10% will have a zero CACS.
I’ve been asked what the upper limit is for CACS but I don’t think there is one. I’ve seen numerous patients with scores greater than two thousand and a few with scores above five thousand.
These graphs show individuals in the lowest age decile having scores over 2981.
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.