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Very High Levels of Calcium in the Arteries Linked to Heart Attacks and Strokes

CardioSmart News

People free of heart disease who have very high levels of calcium in the walls of the heart’s arteries are markedly more likely to have a heart attack, stroke and other heart-related events, or develop other health conditions compared with people who have less or no calcium buildup, according to a study published in Circulation.

Coronary artery calcium (CAC), measured on an imaging scan, is increasingly being used as a tool – in addition to standard risk calculators – to gauge how likely someone is to develop heart disease or have a heart attack or stroke. This score gives information that can help guide treatment decisions, such as the need to go on a statin or intensify lifestyle changes to lower their risk.

Higher CAC scores mean there is more evidence of calcium and thickening in the inside lining of the arteries. Researchers explain that people with CAC scores of >300 or >400 are generally considered to be at highest risk of developing heart disease or having an event such as a heart attack or stroke. But what about people whose score is at or above 1,000?

Researchers sought to investigate their risk compared with people who had lower CAC scores as it relates not only to cardiovascular events and deaths, but also for developing other chronic conditions. They included data from 6,814 participants (age 45-84 years) enrolled in the Multi-Ethnic Study of Atherosclerosis (MESA), a community-based population study, sponsored by the National Heart, Lung, and Blood Institute, of diverse adults free of known cardiovascular disease and followed over many years.

Information about lifestyle and known risk factors for cardiovascular disease, including family history of heart attack, smoking, diabetes, obesity/overweight, and CAC scores, was collected at the start of the study between July 2000 and September 2002. Participants were followed for an average of nearly 16 years. Medical chart reviews and phone interviews were done at 9- and 12-month intervals to collect information about any hospital admissions, onset of new conditions/diagnoses, procedures or deaths. Participants were grouped based on CAC score: 0, 1-399, 400-999, and ≥1,000. Only 3.8% (257 participants) had CAC at or higher than 1,000. 

Overall, people with CAC ≥1,000 tended to be older, male, and white, and had a higher 10-year atherosclerotic cardiovascular disease (ASCVD) risk score on average. They also had a more extensive pattern of calcium buildup (evident in more of the heart’s vessels and over a larger area), but similar average CAC density – the concentration of calcium buildup compared with those with lower CAC scores. That means patients with very high CAC scores had more calcium buildup spread throughout their arteries, but those lesions weren’t more heavily calcified than those with lower CAC scores. But still the more calcium buildup, the higher the chance of heart attacks or strokes in the future.

People with CAC ≥1,000 were substantially more likely to have a cardiovascular event (for example, heart attack, stroke, chest pain due to blockages, or heart-related death) or to die of any cause compared with people who had no evidence of CAC or with CAC 400-999 after accounting for factors known to increase the risk of heart disease. As well, compared with people with CAC=0, those with the highest CAC had almost double the chance of developing other conditions including cancer, chronic kidney disease, pneumonia, chronic obstructive pulmonary disease (COPD) and hip fracture. Researchers said this finding supports the idea that CAC is not only a marker for atherosclerosis, but also older age and undetected organ injury.

They wrote, “[CAC] reflects an individual’s vulnerability to risk factors and can help predict the risk of developing future chronic disease, such as cancer and chronic kidney disease, in addition to its usefulness as a risk predictor for cardiovascular disease events.”

They said the findings underscore a need to recognize that this group of patients, initially free of heart disease, may have the same or higher cardiovascular risk as some patients with established heart disease who’ve had a cardiac event and should “have the opportunity to receive the same aggressive treatment.” The researchers compared event rates for participants without known heart disease (MESA study) with those in another trial involving people with known heart disease. The results suggested that certain patients with very high CAC scores without known heart disease could be at higher risk than some stable patients being treated for heart disease.   

More research is needed, especially as participants with a CAC score of 1,000 or higher were small in number overall (257 total).

For more information about coronary calcium scoring, visit CardioSmart.org/CAC.

Very High Coronary Artery Calcium (CAC ≥ 1000) and Association with CVD Events, Non-CVD Outcomes, and Mortality: Results from The Multi-Ethnic Study of Atherosclerosis (MESA),” Circulation, March 2.

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