Can CAC Screening Help Prevent Heart Attacks?

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Posted on Dec 27, 2019, 3 p.m.

70% or more of patients arriving at the hospital for an emergency intervention for a serious heart attack have not been previously diagnosed with heart disease. Heart attacks arrive acutely and often with no warning, but the disease process building up to that point is typically slower and a chronic one; typically being caused by an arterial blockage that starves heart muscle of oxygen and blood flow over time.

Atherosclerosis is the cause of the blockage in most cases, which is scarring of blood vessels due to inflammation and damage caused by smoking, bad cholesterol, diabetes, high blood pressure, and family history/genetics factors. 

If risk factors are not controlled the scarring process over time will lead to the arteries becoming increasingly narrow,  and eventually calcium deposits will build within the athereosclerotic scar. Calcium is a marker for maturing atherosclerosis, X-rays do not penetrate these deposits very well so on a CT scan or X-ray healthy bones and diseased arteries appear white. 

CAC screening utilizes CT scans to help determine whether any arteries are blocked, while this is not a new test it is increasingly being recognized as an important tool for helping to determine which patients have more advanced atherosclerotic cardiovascular disease as well as those that are at the highest risk of experiencing a heart attack or stroke. 

Recently the American College of Cardiology/American Heart Association released an updated guideline that recommends utilizing coronary artery calcium screening for those who have borderline or intermediate risk of ASCVD as determined by an ASCVD risk factor tool. There are a number of these tools that use various risk factors to calculate the likelihood of experiencing a heart attack or stroke within the next 10 years, but this is a probability not a certainty. High risk is greater than 20%, intermediate risk is between 7.5-20%, borderline risk is between 5-7.5%, and low risk is less than 5% risk. 

In a perfect world where no one has accidents, and every one is within their ideal BMI range, with perfect blood pressure, optimal cholesterol levels, never smokes, and is without diabetes these risk factors would be nothing and not provoke any anxiety at all. But even with these either not being a risk factor or being tightly controlled to the point of not being a serious concern there is still another major risk factor, and that is growing older, which is not reversible, at least not yet, practically speaking.

Ultimately we could all us a little motivation to take better care of our health, but most often this will not come without effort such as diet control, weight loss, exercise, and in some cases medications. Most of us feel more motivated when risks and rewards are higher, what could be higher than a probability of experiencing a heart attack or stroke in the immediate future? 

Dr. Michael Miedema, a cardiologist at the Minneapolis Heart Institute, who specializes in heart disease prevention, is a fan of CAC scoring: “It’s, basically, the only test we have that trumps age in terms of its ability to predict cardiovascular mortality,” Miedema says. “And interestingly, it’s quite predictive of all-cause mortality as well, primarily because of what are called ‘shared risk factors’— things like smoking that not only increase cardiovascular mortality but also increase cancer mortality.”

CAC screening is fairly easy to do, only taking about 10 minutes using 1-1.5 millisieverts of radiation, and it may not be covered by all insurance carriers typically costing from $100-400. In America the average person is exposed to at least 3 mSv of background radiation annually, which is largely from cosmic rays and radon in the home. 

Calcium scoring ranges: 1-10 indicates minimal evidence of coronary artery disease, 11-100 indicates mild evidence, 101-400 indicates moderate evidence, and 400+ indicates extensive coronary artery disease.

There are two major caveats to interpreting calcium scoring: 

1) These are on average as a statistical measurement  a probability not a certainty, and it is not uncommon for patients to routinely defy statistics. A score of zero does not necessarily mean that you don’t have coronary artery disease, rather it could mean that there isn’t the presence of more advanced kinds of atherosclerosis being around long enough to acquire calcium deposit build ups; meaning even with a score of zero you still need to pay attention to controlling risk factors. 

2) The scores are a calculation of the overall atherosclerotic condition in the 2 arteries that feed the heart, but they don’t reliably tell whether it is spread evenly throughout the arteries or whether it has been concentrated to a few tight areas which sometimes requires surgery. A patient may have a score of 600 but the disease may be widely scattered and not narrow to limit blood flow in any particular areas, while another with a score of 300 may have the disease focussed in one ares. Only a coronary angiogram can directly visualize what the arteries look like on the inside.

That brings us to the big question of whether CAC screening can help to prevent a heart attack or not. And the answer is yes, according to Craig Bowron, MD; preventive medicine can be complicated, but for certain patients it appears as if this screening tool can help to provide some clarifying information that will motivate patients to double down and take steps to improve their heart health.