Friday, February 5, 2016

Instruction on Understanding Calcium Scans

Yesterday I had a good conversation with my cardiologist. I have been concerned with my "High" risk scores. See earlier post. He listened to my concern and read the Orange County and Millennium Imaging results and agreed that my risk factor had not changed appreciable, or rolled back, but he showed me why he believes his stress tests get closer to the truth. He sketched the following diagram:
At the top there is a blood vessel with an effective  diameter of 3 centimeters. There is no plaque and the blood flows freely.

Just below there is the same vessel, but the swirls indicate obstructive plaque. The effective diameter is now only 1 centimeter.

But below it, there is still another vessel, with the plaque on the OUTSIDE of the vessel. The vessel is unobstructed and continues to have the full 3 centimeter diameter. A calcium scan may not be able to distinguish between the second and third case. (Now it may be that I should say "calcium" instead of plaque - the scan picks up the calcium with is found with plaque. This is the nature of the indirect measure here.)

So the point is that you could have an unobstructed - or less obstructed vessel - with the same "high" risk score. My cardiologist's point is that it is important to test the blood flow for obstruction. This is done with a stress test or a thallium stress test, both of which I have had. He offered to give me an angiogram, which would test obstruction directly, but I politely declined.

Here is one article that looks at the predictive value of so called risk factors and also for calcium heart scans and finds that neither are as accurate as has been hoped. In fact, neither is "clinically useful." Hmm.

Medicare funds stress tests once a year, so I'll have mine later, in April. That will also be in time to add my cardiologist's recommendations to those of my endocrinologist.

In the meantime, I will up my dose of Crestor slightly, alternating between 2.5 and 5 mg/day. I am now doing 2.5/day. The immediate goal is to reduce my LDL to 75 - again the recommendation of the Orange County Institute five years ago. I had achieved it, but on a greater dosage of Crestor.

He had suggested resuming Zetia, but deferred that until after a lipid profile in April. My endocrinologist wanted me to defer increasing the Crestor dose as described above until I me with my cardiologist, who she hoped would consider the inject-able PCSK9. He was not interested in doing that at this time. If the increased statin-based Crestor can bring my LDL down to the mid-seventies, that would be it. The question is whether I can tolerate that. It's worked before.

I offered to leave lab slips, etc., with my cardiologist, but he was interested only in my last LDL result, which was 99. Talk about getting down to essentials. That is the best predictor of heart incidents I do believe.

1 comment:

  1. Note Mayo Clinic cautions that if you are at low or high risk, calcium heart scans are NOT useful!