According to this week's European Society of Cardiology special issue of The Lancet, a study team led by Dr Michael J Blaha, Ciccarone Center for the Prevention of Heart Disease at the Johns Hopkins Hospital in Baltimore, MD, USA, discovered that coronary artery calcium (CAC) is a much better predictor of heart attack and stroke in apparently healthy adults compared to the level of C-reactive protein (CRP). Therefore, CAC levels, which directly measure atherosclerosis in coronary arteries, may be better at identifying those patients most likely to benefit from statin treatment.

The initial use for statins was for the treatment of patients with high cholesterol levels; however, a previous study (JUPITER trial) established that healthy patients with normal cholesterol, but higher levels of CRP (an inflammatory marker), also benefited from statin treatment.

Researchers conducted this new study using 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 obtained by using a CT scan of the heart.

The researchers discovered, that 47% of MESA patients eligible for JUPITER had CAC scores of 0 with extremely low rates of coronary heart disease events (0.8 per 1000 person-years) in this group.

A group of 25% of participants had CAC scores of more than 100 (20 per 1000 person-years) registering 74% of all coronary events.

95% of all heart attacks in the study population occurred in people with some measurable level of CAC.

In contrast to 13% of those with the highest levels of coronary calcium (scores >100) suffering from a heart attack or stroke during the study, only 2% of those with high CRP but no detectable levels of CAC did so.

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. The statistics were calculated by using the 46% cardiovascular event reduction observed with statins in JUPITER.

The researchers calculated that 124 patients, including those with heart attacks or stroke, would need statin treatment for 5 years to prevent one event, but this number decreases to 19 for those with the highest CAC scores.

To sum up the study, simple presence of CAC was linked to a 4.3 times higher 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 were not linked to adverse events after accounting for routinely measured risk factors. It is significant to mention, that CAC predicts heart attacks and strokes equally well regardless of the CRP level.

The authors say, "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 added, "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."

Researchers state that their results support previous studies that CAC has better predictive value than CRP, but extends that finding specifically to patients with normal cholesterol levels.

They say in a concluding statement:

"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."

Dr Axel Schmermund and Dr Thomas Voigtländer from the Cardioangiologisches Centrum Bethanien in Frankfurt, Germany, say in a linked comment, 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.

Petra Rattue

Tag Cloud