A study in this week's European Society of Cardiology special issue of The Lancet shows that coronary artery calcium (CAC) is a much better predictor of heart attack and stroke in apparently healthy adults than is the level of C-reactive protein (CRP). Thus CAC levels, which directly measure atherosclerosis in coronary arteries, may be better at identifying those patients most likely to benefit from statin treatment. The study is by Dr Michael J Blaha, Ciccarone Center for the Prevention of Heart Disease, Johns Hopkins Hospital, Baltimore, MD, USA, and colleagues.
Statins were initially used to treat patients with high levels of cholesterol only. But in a previous study (the JUPITER trial), it was established that healthy patients with normal cholesterol but higher levels of CRP (an inflammatory marker) benefited from statin treatment. In this new study, the authors took 950 patients from the Multi-Ethnic Study of Atherosclerosis (MESA) who would have been eligible for JUPITER, and looked at how CAC could establish risk. CAC levels were determined using a CT scan of the heart.
The researchers found that 47% of MESA patients eligible for JUPITER had CAC scores of 0 and, in this group, rates of coronary heart disease events were extremely low (0•8 per 1000 person-years). 74% of all coronary events were in the 25% of participants with CAC scores of more than 100 (20 per 1000 person-years). 95% of all heart attacks in the study population occurred in people with some measurable level of CAC. And while 13% of those with highest levels of coronary calcium (scores >100) had a heart attack or stroke during the study, only 2% of those with high CRP but no detectable levels of CAC did so.
Using the 46% cardiovascular event reduction observed with statins in JUPITER, the authors calculated that to prevent one heart attack in people with a CAC score of 0, 549 people would need treatment with statins for 5 years, compared with only 24 for those with CAC scores over 100. Including strokes as well as heart attacks in their calculations, the authors determined that 124 patients would need statin treatment for 5 years to prevent one event, but this number decreases to 19 for those with the highest CAC scores.
Overall, simple presence of CAC was associated with a 4.3 times increased risk of coronary heart disease (interruption of the blood supply to the heart muscle due to fatty deposits in the coronary arteries, leading to heart attacks) and a 2.6 times increased risk of cardiovascular disease (heart attacks or stroke). High levels of CRP had no association with adverse events after accounting for routinely measured risk factors. Importantly, CAC predicts heart attacks and strokes equally well regardless of the CRP level.
The authors say that future guidelines for primary prevention of cardiovascular disease and coronary heart disease should include CAC for those patients that have normal cholesterol but some other risk factor, including obesity, pre-diabetes/metabolic syndrome, or a family history of heart disease. Dr Blaha says*: "We think that it is time to move past traditional risk factors and blood tests and toward incorporation of direct measures of subclinical atherosclerosis in risk prediction. This makes sense because CAC uses modern technology to directly measure the disease we propose to treat with statins."
The authors say that their results agree with previous studies that CAC has better predictive value than CRP, but extends that finding specifically to patients with normal cholesterol levels. They conclude: "Our results are consistent with the hypothesis that focus of treatment on the subset of individuals who have low LDL cholesterol with measurable atherosclerosis could represent a more appropriate allocation of resources, and reduce overall health-care cost, while preventing a similar number of events."
In a linked Comment, Dr Axel Schmermund and Dr Thomas Voigtländer, Cardioangiologisches Centrum Bethanien, Frankfurt, Germany, say that the study shows that, regarding cardiovascular disease, there is a much stronger case for the predictive value of CAC than for CRP, and they are already incorporating CAC into the treatment strategies at their clinic*.
For Dr Michael J Blaha, Division of Cardiology, Johns Hopkins Hospital, Baltimore, MD, USA, please contact Ellen Beth Levitt, Media Relations. T) +1 410-955-5307 E) eblevitt@jhmi.edu
Dr Axel Schmermund and Dr Thomas Voigtländer, Cardioangiologisches Centrum Bethanien, Frankfurt, Germany. T) +49 69 9450 28-0 E) A.Schmermund@ccb.de
Note to editors: *quote direct from author, not found in text of Article
**see figure in full Comment
Journal
The Lancet