Heart scan tomfoolery 2

In the last Heart Scan Blog post, I discussed the significance of the apparent discrepancy between Steve's heart scan score and volume score. This post addresses his second question, also a FAQ about heart scan scores.

Steve noted that his second scan compared to his first showed:

- Left Main volume went up from 22.4 to 35.6
- LAD went down from 95.2 to 91.3
- LCX volume went down from 23.2 to 0
- RCA volume went up from 0 to 9.3

So there are apparent divergences in behavior in the left main that increased and both LAD (left anterior descending) and LCX (left circumflex) that decreased.

The explanation is simple: When heart scans are "scored," they are viewed in horizontal "slices." When the heart is viewed as horizontal slices, the LAD and LCX originate from the common left main stem. In other words, it's like a tree with the left mainsteam representing the trunk, the LAD and LCX representing two main branches.

Plaque can form, obviously, in all three arteries, but it can do so by starting in the left main, for instance, and extending into either the LAD or LCX, or both. The left main plaque can therefore bridge any 2 or all 3 arteries.

When the plaque is "scored" by taking the computer mouse and circling the calcified plaque in question (to allow the computer program to generate the calcium score and volume score of that particular plaque), the plaque that may extend from left main into the LAD and/or LCX might be labeled "left main," or it might be labeled "LAD" or "LCX." There is no reliable way to "dissect" apart the plaque into the three arteries, since the plaque is coalescent and continuous. So the scoring technologist or physician simply arbitrarily declares the artery "LAD," for instance.

The problem comes when two different interpretation methods are used: Perhaps it's a new technologist or physician, or there was no attention paid to how the previous scan was read. One reader calls it "left main" and the next calls it "LCX."

So the apparent discrepancy has to do with flaws in the methods of segregating plaque location, as well as inattention to scoring techniques. The total score, however, remains unaffected.

Nonetheless, Steve has enjoyed a modest reduction in the score of the left main/LAD/LCX from his original 140.8 down to a second left main/LAD/LCX score of 126.9.

The right coronary artery (RCA), however, is not subject to this difficulty and Steve score shows a modest increase in score. (Why the divergent behavior between left main/LAD/LCX and RCA? There is no clear explanation for this, unfortunately.)

All in all, the news for Steve is good: He achieved these results on his own using nutritional techniques. Because he, in all practicality, stopped the progression of his heart scan score and avoided the "natural" rate of increase of 30% per year, all he needs to do is "tweak" his program a bit to achieve reversal, i.e., reduction of score.

Here's an image from another previous Heart Scan Blog post (about the relationship of osteoporosis and coronary disease) that shows such a plaque that starts in the left mainstem yet extends into both the LAD and LCX:

Comments (2) -

  • Leigh

    11/9/2010 8:14:33 PM |

    I am concerned about the amount of radiation in one heart scan, not to mention having one done every year or even five years. When I called my hospital and inquired about the amount of heart scan radiation, I was told it was equivalent to about 30 chest x-rays.

    If I gain knowledge of my heart's condition, but end up with cancer, what have I accomplished?

  • Dr. William Davis

    11/10/2010 12:39:42 AM |

    Hi, Leigh--

    Your hospital told you wrong.

    A 64-slice MDCT device exposes you to around 8 chest x-rays equivalent of radiation. Not great, but not bad.

    Too bad there's no alternative.