Coronary Calcium Score - No Doctor's Order?
Coronary calcium scoring (CCS) is arguably the best method to screen for coronary artery disease. The most interesting part of this test is the direct-to-consumer advertising that occurs to the public.
There are not too many medical tests (especially those with radiation exposure) that anyone can purchase at an affordable price without a doctor's order. Vascular screening is another example. Is it really appropriate for hospitals and offices to allow anyone to walk in and have a coronary calcium score performed? Hmmm ... good question.
First, let me briefly describe what coronary calcium scoring is for those not familiar with the test. This test uses computed tomography (CT) without IV contrast to scan the heart. It is quick and painless, literally taking only minutes. Calcium is quite bright on a CT scan and easily visualized. Computer programs can easily identify and quantify how much calcium is detected on CT in any individual using what is called the Agatston score. The higher the amount of calcium detected, the higher the risk for a coronary stenosis, acute coronary syndrome and cardiac death.
What data support the use of calcium scoring to screen for coronary disease? There is a difference between a test having predictive value of cardiovascular disease and one that has actually been shown to improve clinical outcomes. Predicting risk is nice, but we really should focus on things that reduce morbidity and mortality. The predictive data are strong that scores of 0 have a very low risk (< 1%) of a cardiovascular event within 3 to 5 years. On the other side, a score > 100 in one study showed a 7-fold increased risk for cardiovascular events compared with those with no detectable coronary calcium. To this date, there are no data to show that the act of screening for coronary calcium reduces cardiac events or mortality. However, it would make common sense that an asymptomatic 55-year-old with an Agatston coronary calcium score of 1,000 who was not taking aspirin or an HMG-CoA reductase inhibitor would have a better outcome if they started one, right? There is no definitive evidence to support this, yet.
In my opinion, as long as a proper screening process is in place to ensure that those with a low pre-test probability and those with a high pre-test probability do not inappropriately have coronary calcium scoring performed, then I think it is quite a good service to offer. I have personally started coronary calcium scoring programs at more than one facility. While the volume of patients getting the test where I practice is low (perhaps one per day), we do have a thorough questionnaire to ensure that only intermediate-risk individuals receive the test. No doctor's order is necessary and the cost is an affordable $99. Each patient receives a phone call from a cardiologist to discuss the results of their scan and answer questions. We require the patient list a primary care physician so the results have a place to go and do not get lost in space.
Note that a coronary calcium score IS NOT a test to see if a patient’s symptoms are heart-related. To evaluate chest pain or other potential anginal symptoms, stress testing is the preferred method. A person’s calcium score could be quite high without any obstructive coronary stenosis (and vise versa). It is important to keep this test as a risk assessment only. Patients may have a different perception if not well educated and might have the scan done to see if their “heartburn” is really from their heart. This is quite inappropriate and potentially dangerous. Look at this image below showing a CT of a coronary vessel with extensive calcification, then look at the correlating invasive coronary angiogram showing absolutely no flow-limiting stenosis:
There are many stories you may hear, both good and bad, surrounding calcium scoring. The most notable is the previously healthy individual (sometimes even quite athletic) without any symptoms of angina or heart disease who gets a coronary calcium score performed and has an astronomically high score. Hmmm ... if the person has no symptoms, do we really need to revascularize the coronary stenosis with stents of surgical bypass? Not necessarily, but that's a different topic. Certainly, even if no coronary intervention is needed, an abnormal calcium score can be quite an eye-opener. Aspirin and HMG-CoA reductase inhibitors may be recommended in many cases when the calcium score is high for primary prevention of clinical heart disease. Again, remember that a high calcium score does not necessarily mean that a coronary stenosis is present, although it is more likely.
How about the opposite scenario? A person who has a perfect calcium score of 0. Could that individual still suffer a heart attack? Absolutely! I always tell patients that when their score is 0 it is not a free pass to party and be unhealthy. Coronary calcium scoring only detects calcium, as the name implies. Could there be a soft plaque made predominantly of cholesterol? Sure. Take a look at the image below showing a severe coronary stenosis without any calcification on CT scanning and the associated invasive coronary angiography image:
We also know that the plaques with little or no calcium tend to have thin, fibrous caps and are more prone to ulceration or rupture, causing an acute coronary syndrome. To date there is no good clinically applicable way to perform coronary plaque characterization that will predict which plaque is susceptible to rupture.
So, to get a coronary calcium score or not? Is it worth the 0.9 mSv to 2.4 mSv of radiation exposure? If you are a middle-aged person with no previous heart disease diagnosis or risk equivalent (diabetes or peripheral arterial disease), no potential anginal symptoms, and some risk factors for heart disease such as hypertension, tobacco use, dyslipidemia or a family history of ischemic heart disease, then this test is for you ... as long as you understand and accept the risk of radiation exposure, which is low but present. Perhaps every 3 years the test can be repeated to assess for any change, however no more frequently than that. It is probably one of the best ways the appropriate person could spend $99, in my opinion!