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“Heart scans for detecting disease” (Published July 6, 2000)

There has been a burst of advertising over the last few years about using computed tomography, colloquially known as CT, to detect heart disease, purportedly so early that you can prevent its worsening or intervene before it manifests itself. The idea of early intervention is appealing, of course, but there are caveats that should give one pause before blithely paying for the test.

First, the premise of the CT heart scan is that the mineral, calcium, deposits in diseased blood vessels, and that more calcium deposits mean more disease. Special X-ray machines, known as ultrafast or modern helical CT scanners, are very sensitive detectors of such calcium deposits. This has been a fruitful area of heart research for over a decade and the correlation of calcium deposits to the degree and number of obstructing blood vessels has been generally validated. I am not critical of the science; in fact, during my years at NIH over 25 years ago (arrrgh!), my research team was one of the first groups to actually report the relationship of calcium deposits and coronary artery disease in a national medical journal.

So, what's the problem? Like so many things in medicine today, it's not the science, but the application of the science that leads to potential misuse of information. Everyone would naturally like to know about heart disease before it “gets you”. I tell my patients it's like seeing the mugger before he can attack you. People's fears of heart disease mean they're willing to spend money to detect it. Human nature means there are business opportunities to help patients spend that money. Marketing or commercial interests may stretch or alter the science platform to get patients to want to spend their money.

Some CT advocates saying that knowing the results of the CT scan is more important than knowing their cholesterol or blood pressure have appalled me. That statement can be made since having a high calcium score predicts more obstruction than those isolated lab numbers. This conveniently ignores the fact that calcium deposits simply are markers for closed blood vessels that were caused by elevated cholesterol, high blood pressure or other risk factors.

A fallacious and misleading corollary is that a normal CT scan means you don't have to worry about having closed blood vessels. Doctors have learned in the last few years that the closure that causes heart attacks are NOT the significantly closed, calcified areas of the blood vessel. In fact, the nonobstructing, so called “vulnerable”, closures are generally not calcified and thus not detectable by CT scans. So the mugger that gets most people is cloaked so as not to be visible. The most sensitive tool doctors actually use to find these vulnerable closures is a small ultrasound device that can be passed down the blood vessels themselves to scan the walls directly. These devices have confirmed that the abnormalities we now know to be the likeliest muggers more often have no calcium deposits at all.

I am not saying that these tests have no value. If the calcium score is high, you have significantly greater chance of having seriously closed blood vessels. Seeing your doctor to confirm or deny that possibility is the next best thing you can do. But the best thing you can do is to avoid having heart disease in the first place by taking care to have a healthy lifestyle and detecting and correcting all known risk factors for premature heart disease.

 

 
   
   

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