The Nation's Health + [Heart scans]

“Too many false positives”

“Do you really think I need a heart scan?” asked Terry.

“My doctor said that heart scans show too many false positives. He says that many people end up getting unnecessary heart catheterizations because of them.”

At age 56, Terry was becoming increasingly frightened. His father had suffered his first heart attack at age 53, Terry’s paternal uncle had a heart attack at age 56, his paternal grandfather a heart attack at age 50.

Is this true? Do heart scans yield too many false positives, meaning abnormal results when there really is no abnormality?

No, it is not. What Terry’s doctor is referring to is the fact that, in the decades-long process that leads to heart attack, heart scans have the ability to detect early phases of developing coronary atherosclerotic plaque.

Let’s take Terry’s case, for example. Given his family history, it is quite likely that he does indeed have coronary atherosclerotic plaque. Will it be detectable by performing a stress test? Probably not. In fact, Terry jogs and feels well while doing so. While a stress test abnormality that fails to reach conscious perception is possible, it’s fairly unlikely given his exercise routine.

Will Terry’s coronary atherosclerotic plaque be detectable by heart catheterization? Very likely. But why perform an invasive hospital procedure just as a screening test? Should a woman wishing to undergo a screening test for breast cancer undergo breast removal? Of course not.

Is waiting for symptoms a rational way to approach diagnosis of heart disease? Well, when symptoms appear, it means that coronary blood flow is reduced. Stents and bypass surgery may be indicated. The risk of heart attack and death skyrocket. Sudden death becomes a real possibility.

In the 30 or so years required to establish sufficient coronary plaque to permit the appearance of symptoms or the development of an abnormality detectable by stress testing, there were many years when the disease was early--too early to generate symptoms, too early to be detectable by stress testing.

That’s when heart scans uncover evidence for silent coronary atherosclerotic plaque.

Should we call this a “false positive” just because it doesn’t also correlate with “need” for a catheterization, stent, bypass operation or result in heart attack within the next few weeks?

The detection of early plaque is just that: early disease detection.

Imagine, for instance, that the breast cancer that will grow into a palpable nodule or mass detectable by mammogram is detectable by a special breast scan 15 years before it becomes a full-blown tumor, metastasizing to other organs. What if effective means to halt that earliest evidence of cancer could put a stop to this devastating disease decades ahead of danger? Is this a “false positive” too?

In my view, this is the knuckleheaded thinking of the conventional practitioner: “Don’t bother me until you’re really sick.” Prevention is a practice that has become fashionable only because of the push of the drug industry. Nutrition is an afterthought, a message conceived through consensus of “experts” with suspect motivations and allegiances.

So, no, heart scans do not uncover “false positives.” They uncover early disease--true positives--years before it is detectable by standard tests or by the appearance of catastrophe. But that is the whole point: Early detection means getting a head start on prevention.

Do heart scans lead to unnecessary heart catheterizations? Yes, sadly they do. But not because heart scans are false positive. It happens because of unscrupulous or ignorant cardiologists who use the information wrongly. In my view, heart scans should NEVER lead directly to heart catheterization in an asymptomatic patient. Heart scans, as helpful as they are, do not modify the standard reasons for performing heart procedures.

If a car mechanic is dishonest and fixes a carburetor that didn't need fixing, should we condemn all car mechanics? No, of course not. We only need to develop the means to weed out the bad apples. The same applies to heart scans.