Coronary heart disease, a new method helps find out who is at risk and more suitable for statins

Coronary artery disease: new method to understand who is most at risk

Certain conditions, such as high cholesterol, predispose to coronary artery disease. The absence of traditional risk factors, however, does not always rule out the risk of heart disease. Coronary calcium determination represents a tool that can more accurately reclassify patients at risk, providing the physician with the ability to select those who really need statin drug therapy.

This is the finding of two recent studies; one conducted by researchers at Baptist Health South Florida in Miami, the other by researchers at the University of Washington in Seattle, both published in the Journal of American College of Cardiology.

Coronary artery disease and statins

Coronary artery disease is the most common of cardiovascular diseases, accounting for one of the leading causes of death among adults in most European countries. Coronary artery disease results from narrowing of the coronary arteries by the presence of atherosclerotic plaques, thickenings of the inner wall of the arteries, formed mainly of lipids, proteins, and calcium deposits. Atherosclerotic plaques reduce blood flow and increase the chances of a clot forming, which can block blood flow and cause a heart attack. Genetic predisposition, age and gender are just some of the factors that promote atherosclerosis. In contrast to these, other conditions that increase the risk of developing coronary artery disease can be modified by a healthier lifestyle and are:

• Cigarette smoking
• High blood pressure
• High cholesterol
• Lack of exercise
• Stress
• Diabetes
• Overweight and Obesity
• Alcohol consumption

Among these, the most important risk factor is high cholesterol. When modifying diet is not enough to reduce cholesterol, drug therapy can be used. The most common is statins, drugs that in addition to reducing the production of endogenous cholesterol (that produced by the body) can prevent cardiovascular damage in at-risk individuals and counteract the formation of atherosclerotic plaques. 

Statins are prescribed by physicians to those whose cholesterol levels, and other predisposing factors, reach a threshold value set by guidelines. In recent years, guidelines from the American College of Cardiology and the American Heart Association have greatly expanded the range of individuals who need statin therapy.

Coronary calcium, an effective diagnostic tool

Several studies have shown the enormous potential of coronary calcium, in addition to traditional risk factors, to define the likelihood of heart disease. In normal arteries, calcifications are not present, and their presence is an indication of coronary artery disease, and the extent of calcifications correlates with that of plaque.

However, to date, no risk calculation including coronary calcium has been developed. The two new U.S. researches show that coronary calcium determination can reclassify patients at cardiovascular risk, better identifying, than current guidelines indicate, those who should follow drug therapy.

What did the researchers find?

Both researches were carried out as part of a large study, the Multi Ethnic Study of Atherosclerosis (MESA), which involved 6,814 subjects, men and women, aged 45 to 84 years, from different communities in the U.S. (non-Hispanic whites, Chinese Americans, African Americans, and Hispanic Americans). All subjects were followed for 10 years, and were free of heart disease at the start of the project. In the first study, researchers, led by Khurram Nasir, evaluated the consequences of coronary calcium deficiency in determining subjects at risk for atherosclerotic cardiovascular disease and eligible for statin therapy. 

According to American College of Cardiology and American Heart Association guidelines, 77 percent of all subjects included in the study would have been candidates for statin therapy, but of these many subjects had a coronary calcium value of zero. The researchers calculated that the absence of coronary calcium was associated with a very low risk of disease-with an incidence of 4.2 per 1,000 person-years-and especially below the threshold above which drug therapy is prescribed. As a result of this assessment, nearly half of patients, 44%, were reclassified from a risk status where statins are recommended to one where they are not needed. 

The objective of the study led by Robyn McClelland instead was to derive and validate a method for calculating the probability of developing coronary artery disease that included, in addition to risk factors, coronary calcium deposition values. The authors obtained an index that was able to discriminate more accurately, compared with the calculation formulated with classical risk factors alone, the probability of cardiovascular events. This new MESA risk score is available online and can be easily used by physicians to determine treatment strategies and during patient risk communication.

A new diagnostic tool?

According to the reports of these studies, coronary calcium determination could be a new diagnostic tool that can provide proper cardiovascular risk stratification. In particular, as confirmed by Donald Lloyd Jones of Northwestern University Feinberg School of Medicine, Chicago, coronary calcium determination is useful in classifying those who might have acute cardiovascular events into low- and intermediate-risk subgroups, as it identifies disease better than risk factors alone.  

Sources: Nasir K, Bittencourt MS, Blaha MJ, Blankstein R, Agatson AS, Rivera JJ, Miemdema MD, Sibley CT, Shaw LJ, Blumenthal RS, Budoff MJ, Krumholz HM. Implications of Coronary Artery Calcium Testing Among Statin Candidates According to American College of Cardiology/American Heart Association Cholesterol Management Guidelines: MESA (Multi-Ethnic Study of Atherosclerosis). J Am Coll Cardiol. 2015 Oct 13;66(15):1657-68. Robyn L. McClelland, et al, "10-Year Coronary Heart Disease Risk Prediction Using Coronary Artery Calcium and Traditional Risk Factors: Derivation in the MESA (Multi-Ethnic Study of Atherosclerosis) With Validation in the HNR (Heinz Nixdorf Recall) Study and the DHS (Dallas Heart Study).