Coronary Heart Disease: A New Method Helps Discover Who Is At Risk And Best Suited For Statins

Coronary Disease: New Method to Identify Who is at Higher Risk

Certain conditions, such as high cholesterol, predispose individuals to coronary artery disease. However, the absence of traditional risk factors does not always exclude the risk of heart disease. Measuring coronary calcium represents a tool capable of more accurately reclassifying patients at risk, giving doctors the ability to select those who truly need pharmacological therapy with statins.

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

Coronary Disease and Statins

Coronary artery disease is the most common cardiovascular disease and represents one of the leading causes of death among adults in most European countries. Coronary artery disease results from the narrowing of the coronary arteries due to atherosclerotic plaques, which are thickenings of the inner artery walls mainly formed by lipids, proteins, and calcium deposits. Atherosclerotic plaques reduce blood flow and increase the likelihood of clot formation that can block blood flow and cause a heart attack. Genetic predisposition, age, and sex are just some of the factors that promote atherosclerosis. Unlike these, other conditions that increase the risk of developing coronary disease can be modified by a healthier lifestyle and include:

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

Among these, the most important risk factor is high cholesterol. When dietary changes are not sufficient to reduce cholesterol, pharmacological therapy may be used. The most common treatment is based on statins, drugs that not only reduce endogenous cholesterol production (cholesterol produced by the body) but can also prevent cardiovascular damage in at-risk individuals and counteract the formation of atherosclerotic plaques. 

Statins are prescribed by doctors to those who have cholesterol levels and other predisposing factors that reach a threshold value established by guidelines. In recent years, the guidelines of the American College of Cardiology and the American Heart Association have greatly expanded the range of subjects who require statin therapy.

Coronary Calcium, an Effective Diagnostic Tool

Several studies have demonstrated the huge potential of coronary calcium, in addition to traditional risk factors, to define the probability of heart disease. Normal arteries do not have calcifications, and their presence indicates coronary disease, with the extent of calcifications correlating with that of the plaque.

However, to date, no risk calculation including coronary calcium has been developed. The two new American studies show that coronary calcium measurement can reclassify patients at cardiovascular risk, better identifying, compared to current guideline indications, those who should follow pharmacological therapy.

What Did the Researchers Find?

Both studies were conducted 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, belonging to various US communities (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 the absence of coronary calcium in determining subjects at risk of atherosclerotic cardiovascular disease and eligible for statin therapy. 

According to guidelines from the American College of Cardiology and the American Heart Association, 77% of all subjects included in the study would have been candidates for statin therapy, but many of these subjects had a coronary calcium score of zero. The researchers calculated that the absence of coronary calcium was associated with a very low disease risk—with an incidence of 4.2 per 1000 person-years—and especially below the threshold at which pharmacological therapy is prescribed. Thanks to this evaluation, nearly half of the patients, 44%, were reclassified from a risk state recommending statins to one where they were not necessary. 

The aim of the study led by Robyn McClelland was to develop and validate a method to calculate the probability of developing coronary disease that included, in addition to risk factors, coronary calcium deposits. The authors obtained an index capable of more precisely discriminating, compared to calculations based only on classical risk factors, the probability of cardiovascular events. This new MESA risk score is available online and can be easily used by doctors to determine treatment strategies and during risk communication with the patient.

A New Diagnostic Tool?

According to these studies, measuring coronary calcium could represent a new diagnostic tool capable of providing correct cardiovascular risk stratification. In particular, as confirmed by Donald Lloyd Jones of Northwestern University Feinberg School of Medicine, Chicago, coronary calcium measurement is useful in classifying those who might have acute cardiovascular events into low and medium 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).