A heart calcium scan: What does it mean?
Just like the "bone spur" of the heel ligament, inflamed soft tissues become calcified over time. Some patients ask, "Should I stop drinking milk?" The calcium isn't the problem. Inflammation is.
Calcium in arteries is a marker for inflammation. Although it is not the source of the inflammation, calcium is a very useful marker.
Inflammation, or plaque in the arteries is caused by risk factors like high blood pressure, smoking, diabetes and high cholesterol.
Although easy and popular, risk factor-based calculators are not as accurate at predicting heart attacks as the actual patients' arteries (1, 2).
Examples of Heart Calcium Scans
Coronary arteries are normally clean, with no calcium. Calcification appears as white spots in the arteries.
There are two good non-invasive ways to assess how much plaque is in the arteries: CT calcium scores and ultrasound. The problem with CT scans is that they are currently being done by many hospitals with older sub-standard equipment. Because the coronary arteries are in motion with every heart beat, if the CT detection ring moves around the patient's chest too slowly, artery images are blurred. So these slower CT heart scans miss too many high-risk patients, because they are not as sensitive in detecting calcium as the Electron Beam CT with no moving parts, which captures images at the speed of light.
pick the right ct machine:
In addition to being faster, the electron beam CT gives less radiation compared to conventional CT scan machines. If electron beam CT (or EBCT) is not available in your area, ask how many slices the CT scanner makes per second. How much more motion artifact do you think you'll see with a CT that makes 8 or 16 slices per second compared to a faster one that makes 320 slices per second? Although 64 slices per second gives reliable results when a patient's pulse is not too fast, the faster the CT, the better quality pictures you'll get. Even with 320 slices per second, beta blocker drugs are often used by the radiologist to slow the pulse to get better quality images. Don't be afraid to ask your primary care doctor for a beta blocker to take with you, in case your pulse is too fast for the exam.
why have heart calcium scores been so controversial?
Some cardiologists recommend them. Some recommend against getting them. Click here to see the movie trailer The Widowmaker.
your calcium score:
Your calcium score can tell you something about your risk for having events like heart attacks and sudden death.
The age-and-gender matched "percentile score" represents how diseased your arteries are compared to other men or women your age. So a percentile score of 90% means that 90% of men or women your age have less calcium than you have.
If your calcium score is 0, then your percentile score is also 0.
"Calcium score" is the number representing how much calcium is in your coronaries. Owing to a higher risk of having more severe coronary artery disease, patients with calcium scores over 400 are often sent for a stress test. Calcium scores over 1000 are dangerous, carrying a 25% chance (in one study) of having a heart event in one year (3).
Limitations of Heart Calcium Scans:
All tests have their limits. The limitations of CT calcium scoring are that it can underestimate plaque (and event risk) in patients who
- are younger (men under 45 and women under 50)
- have rapidly progressive plaque disease
- are diabetic
- calcify their plaque more slowly than others (due to genetics)
- have soft plaque, the most dangerous type. Soft plaque, because it is not calcified, doesn't show up on CT calcium scans.
- have chest pain with risk factors but a 0 calcium score (4).
What's the difference? Here's an ultrasound picture of a patient's plaque:
Plaque is the gray stuff inside the artery, next to the red blood flow. Calcium deposits are the white specks.
After screening mammograms locate calcified lesions in the breast, ultrasound technology is employed to get a better picture of the actual breast tissue. In the same way, we use ultrasound technology to get a close-up picture of plaque in the peripheral arteries after calcium has been identified by screening CT heart scans. Combining the CT information from the heart arteries with the ultrasound data from the central and peripheral arteries provides the most thorough and comprehensive non-invasive trending technology available today.
The most important question a doctor can ask is whether plaque is getting worse with therapy, or getting better. When we follow the effects of lifestyle and bio-marker changes on the actual plaque itself, our therapeutic decision-making process has the traction that can only come from the linking together of cause-effect relationships. This is the power of personalized medicine.
Ultrasounds commonly done today are designed to ask the surgical question: "Is there enough flow-limiting obstruction to need a surgical procedure?" Our cutting edge "Ask the Arteries" program, 9 years in development by Dr. Hight, was designed to ask the medical question: "Is the prevention program working or not?" When prevention is working, atherosclerotic plaque stabilizes and then shrinks.
To find out how plaque trending works, press this button and then watch the short video "Does CardioSound get results?"
Obstructive plaque requires surgical procedures because it cuts off the blood supply.
Why has early screening (looking for heart disease before a heart attack) been so controversial?
Click on this link to watch the movie trailer:
- This prospective study of 44,000 patients with no symptoms and no history of coronary disease compares the relative predictive value of risk factors versus heart calcium scores. "Our study findings support a paradigm shift in CVD risk assessment from RF-based (risk factor) approach to detection of sub-clinical atherosclerosis burden as evident by the fact that a significant proportion of those with no RF (risk factors) have a severe amount of coronary atherosclerosis and have a high risk for all-cause mortality. The higher precision of CAC (coronary artery calcium) relative to RFs (risk factors) for identifying at-risk individuals may be because of the fact that CAC is a measure of actual disease that occurs further down the causal pathway than the presence of RFs that are mere surrogates for this process." (parentheses and italics added) Nasir, et al. Interplay of coronary artery calcification and traditional risk factors for the prediction of all-cause mortality in asymptomatic individuals. Circ Cardiovasc Imaging. 2012;5:467-473
- Hecht, et.al. Coronary artery calcium scanning: clinical paradigms for cardiac risk assessment and treatment. Am Heart J. 2006;151:1139-46
- Wayhs, et al. High coronary artery calcium scores pose an extremely elevated risk for hard events. J Am Coll Cardiol. 2002 Jan 16;39(2):225-30
- Although heart calcium scans are a great screening tool for people who don't have symptoms, high risk chest pain patients can have severe blockage even though they have normal heart scans with 0 calcium scores. In this study of 291 patients referred for heart catheterization, 12% of the patients with 0 calcium scores had severe blockage requiring re-vascularization (angioplasty, stent or bypass). Of 64 totally occluded coronary arteries in the study, 20% had no calcium. Patients with severe blockage but normal calcium scores tended to be women or younger men. Gottlieb I, et al. The absence of coronary calcification does not exclude obstructive coronary artery disease or the need for re-vascularization in patients referred for conventional coronary angiography. J Am Coll Cardiol. 2010 Feb 16;55(7):627-34.