Coronary CT angiography is a new screening test to detect blocked arteries
without undergoing an invasive procedure. This technology is relatively new, and exactly how this test will be used,
and which insurance companies will pay for it, may change over the next few years.
Why have a CT angiogram?
The purpose of the test is to evaluate for blocked arteries in the heart
without undergoing an invasive angiogram. The hope for this test is that it may replace stress tests as a better evaluation
of the heart. Patients who present to the emergency room also could have this single test to exclude blocked arteries
in the heart, a tear of the aorta (dissection) and a blood clot to the lungs (pulmonary embolus). Patients at medium
risk for heart disease may benefit from knowing more precisely how much cholesterol is in the coronary arteries. Someday,
this test may be preferred over stress testing, but additional research and familiarity with this technology is needed.
How reliable is the test?
Current studies indicate that significant disease in the coronary is detectable
about 95% of the time in the large vessels. This scan can miss disease in the smaller vessels of the heart. While
these small vessels may still cause symtoms, they are unlikely to cause a significant heart attack. The test is
also about 95% specific, meaning that abnormalities seen are actually present the majority of the time. However,
this test cannot quantitate the degree of blockage precisely, and there are artifacts that may get in the way of good visibility,
such as calcium buildup in the arteries.
Is a stress test still needed?
A CT angiogram will give information as to the extent, severity, and
type of cholesterol build-up in the arteries. A stress test will give information on the clinical significance and size of heart at risk from a
particular blockage. These tests are complimentary and similar, but give different information. If the CT angiogram
indicates severe disease, a stress test is generally not needed, and an angiogram may be the next test. Similarly, if a stress test indicates significant disease,
then a CT angiogram is not needed, and a routine angiogram would be the next step.
Are there risks?
As with an angiogram, there is a risk from IV contrast dye, which rarely
can cause an allergic reaction, or may worsen kidney function. Also, a moderate dose of radiation is needed to
obtain the pictures.
Where is this test available?
Both St. Marks and LDS hospital have a new multidetector 64 bit high resolution CT scan that
has been shown to give the best pictures of the coronary arteries.
An example of a picture of coronary arteries as detected by CT scan.
