Calcium Scan Can Predict Premature Death Risk

A scan of calcium deposits inside your arteries can help doctors deduce how long you’re likely to live, a new study has found.

The test, called a coronary calcium scan, uses a regular CT scan to look for calcium deposits in the three major arteries that carry blood away from the heart, said lead author Leslee Shaw, a professor of cardiology at Emory University in Atlanta.

People with the largest amounts of calcium in their arteries carry an early death risk that’s six times greater than those with no calcium deposits, researchers found in a 15-year study of nearly 10,000 patients.

“If you had no calcium or very small amounts, we were able to track over a very long time that you actually had a very outstanding survival,” Shaw said.

Calcium deposits develop as a response to plaque formation along the artery walls, Shaw said.
These plaques, which are caused by blood cholesterol, build up over time and cause arteries to narrow, leading to heart disease as the heart works harder to pump blood through the body.

If a plaque bursts, a blood clot can form on its surface, blocking blood flow and causing a heart attack, according to the U.S. National Institutes of Health. If the clot breaks free, it can flow into the brain and cause a stroke.

To prevent plaques from bursting, the body tries to harden them by depositing calcium salts over and around them, Shaw said.

In this new study, doctors referred 9,715 healthy patients in the Nashville area between 1996 and 1999 to a cardiology outreach screening program provided by the military’s Tricare Healthcare System. The patients underwent a calcium scan, and also provided a detailed history of their heart risk factors.

Computerized Tomography

Computerized Tomography or CT scan is a marriage between x-ray and a computer. This has several advantages over x-ray. First the images have much more detail than plain film.

Second, the data can be manipulated to depict various planes through the body – frontal, sagittal, coronal, etc. - much like MRI. They can even be viewed in 3D. Finally, the level of x-ray exposure (ionizing radiation) is much reduced.

CT scan, just like plain x-ray, differentiates tissue based on density. The more dense the tissue, the more x-ray is absorbed, the less strikes the computer receptors, the lighter the shade. So bone (very dense) shows up as white and air shows up as black. All the other tissues are in between, showing up as varying shades of gray.

Again, just like x-ray, CT scan sees bone extremely well and the absence of bone (think bone tumor or fracture) is readily seen in contrast. By comparison, MRI sees soft tissue very well, but does not image bone readily. I’ll review MRI in detail next week.

Motion is a real issue for all imaging studies. X-ray solves this issue by taking single exposures in a tenth of a second. CT scan and MRI have issues in this regard as they collect data over a long period of time. So tissues that move, like the heart, lungs, and the digestive tract cannot easily be captured. Blood will appear black as it courses through the arteries and veins of the body.

High speed CT scans eliminates motion allowing clear images of moving tissue. This study can visualize calcium deposits in the artery walls of the heart. The radiologist rates the amount of calcification as the “calcium score”. High calcium scores have led some physicians and many patients to fear calcium intake as a cause of heart disease. However, that fear is misplaced.