by John A. Rumberger, PhD, MD, FACC, FSCCT
The coronary calcium scan or HeartScan has been available since the early 1990’s and is the main subject of the documentary ‘The Widowmaker’ [Netflix] regarding the controversy of finding early heart disease through non-contrast CT and the very profitable treating of advanced heart disease using stents and other devices.
Heart disease remains the single largest cause of death in the US, killing 40% more people than all cancers combined – but unlike screening tests supported by the American Cancer Society such as mammography or colonoscopy – screening for heart disease has not been adopted by the American Heart Association or the American College of Cardiology.
The coronary artery [Agatston] ‘score’ [CAC] is a measure of the volume of the calcified coronary artery plaque which was demonstrated 20 years ago to be a reliable surrogate to the coronary atherosclerotic plaque burden. The supposition has been that the higher the score, the higher the risk – this has essentially been demonstrated in studies with 3 to 5 year follow-up and the question remains if the CAC score retains its predictive power out beyond a decade.
A recently published study [Ann Intern Med, July 7, 2015, vol. 163:1, pp 14-21] in nearly 10,000 asymptomatic individuals who had a non-contrast CT HeartScan in Nashville, TN between 1996 and 1999 looked at a 15+ year follow up on all-cause mortality.
The results of the initial CAC score distributions and subsequent overall all-cause mortality are shown in the table below:
Unadjusted All-Cause Mortality vs. CAC Score
CAC Score CAC Category All-Cause Mortality/year [based on 15 year follow-up]
0 No visible plaque 3% [~0.2% per year]
1-10 Very Mild 6% [~0.4% per year]
11-100 Mild 9% [~0.6% per year]
101-400 Moderate 14% [~0.93% per year]
401-1000 Extensive 21% [~1.5% per year]
>1000 Severe 28% [~1.87% per year]
Although conventional risk factors such as age, high blood pressure, high cholesterol, and family history were also important, age and CAC score remained the top predictors in this 15+ year follow up. For those at the top of the CAC chart, the authors indicated that mortality “is quite high and can approach 30%, 40%, and even 50% over the 15 years.”