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CT coronary angiography is NOT a screening procedure

CT coronary angiography is NOT a screening procedure

28. November 2008 William Davis (3)
I've recently had several hospital employees tell me that their hospitals offered CT coronary angiograms without charge to their employees.

Among these hospital employees were several women in their 30s and 40s.

Why would young, asymptomatic, pre-menopausal women be subjected to the equivalent of 100 chest x-rays or 25 mammograms? Is there an imminent, life-threatening, symptomatic problem here?

All of these women were without symptoms, some were serious exercisers.

There is NO rational justification for performing CT coronary angiography, free or not.

What they really want is some low-risk, yet confident means of identifying risk for heart disease. Cholesterol, of course, is a miserable failure in this arena. Framingham risk scoring? Don't make me laugh.

Step in CT coronary angiography. But does CT coronary angiography provide the answers they are looking for?

Well, it provides some of the answers. It does serve to tell each woman whether she "needs" a heart procedure like heart catheterization, stent, or bypass surgery, since the intent of CT angiography is to identify "severe" blockages, sufficient to justify heart procedures.

Pitfalls: Because of the radiation exposure, CT angiography is not a procedure that can be repeated periodically to reassess the status of any abnormal findings. A CT angiogram every year? After just four years, the equivalent of 400 chest x-rays will have been performed, or 100 mammograms. Cancer becomes a very real risk at this point.

CT angiography is also not quantitative. Sure, it can provide a crude estimation of the percent blockage--the value your cardiologist seeks to "justify" a stent. But it does NOT provide a longitudinal (lengthwise) quantification of plaque volume, a measure of total plaque volume that can be tracked over time.

What's a woman to do? Simple: Get the test that, at least in 2008, provides the only means of gauging total lengthwise coronary plaque volume: a simple CT heart scan, a test performed with an equivalent of 4 - 10 chest x-rays, or 1 - 2.5 mammograms.

Perhaps, in future, software and engineering improvements will be made with CT coronary angiography that reduce radiation to tolerable levels and allows the lengthwise volume measurement of plaque. But that's not how it's done today.
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Comments (3) -

  • Diana Hsieh

    11/29/2008 9:55:00 PM |

    I'm confused by your post.  From what I understand, the CT angiogram provides a superset of the data provided calcium scoring CT.  So when I got a CT angiogram this summer, I got a calcium score with it.  (Is that not standard?)

    Also, I worry that you're overstaing the radiation dose of the CT angiogram.  In a prior blog post, you wrote:

    "CT coronary angiography presents a different story. This is where radiation really escalates and puts the radiation exposure issue in the spotlight. As Dr. Cynthia McCullough's chart shows above, the radiation exposure with CT coronary angiograms is 5-12 mSv, the equivalent of 100 chest x-rays or 20 mammograms. Now that's a problem.

    "The exposure is about the same for a pelvic or abdominal CT. The problem is that some centers are using CT coronary angiograms as screening procedures and even advocating their use annually. This is where the alarm needs to be sounded. These tests, as wonderful as the information and image quality can be, are not screening tests. Just like a pelvic CT, they are diagnostic tests done for legimate medical questions. They are not screening tests to be applied broadly and used year after year."

    I agree with your analysis that the CT angiogram delivers too much radiation to be used as a yearly screening test, but your radiation comparison numbers are way different in the two posts by a factor of four.  While such numbers may not be precise, that seems like a bit much.

    Full disclosure: My husband is a radiologist.  (He's msk not a body guy, so heart scans aren't his thing.)  His group performs both kinds of tests.  I'm definitely not promoting CT angiograms over CT calcium scoring.

  • Diana Hsieh

    11/29/2008 10:38:00 PM |

    OH OH!  I misread your post.  You said that "after four years" -- hence the four-fold increase in radiation.  Duh.  

    My question about the calcium scoring as part of the angiogram remains, however.  (I could repost that as its own comment if you prefer, however.)

  • Amna

    8/3/2011 11:41:22 AM |

    This is done with the help of a device called the catheter which is a thin, narrow, tube-like structure. Now, the images are studied to understand corrective measures needed to re-instill proper functioning of the heart.   Angiography hospital in Thailand

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