False positive stress tests?

My internist recently sent me to a cardiologist. I'm uncertain why, though
I was complaining of excessive tiredness and stated that if this keeps up I will be a frail old man in a few years.

A Cardiolite - adenosine stess test showed abnormal perfusion of the apex.

A resting echo appeared to show reduced ejection fraction, 45, stiffness, enlargment of left ventricle and atrium.

Cardiac catheterization was suggested. As I had no symptoms other than just being excessively tired much of the time and what I considered orthostatic hypotension, I asked if it was possible that the Cardiolite stress test result was an artifact.

To check that, a dobutamine-atropine stress echo study was done. I was told that the wall motion was abnormal and that there was a modest drop in ejection fraction when stressed.

Again, cardiac catheterization was recommended and I was told to anticipate angioplasty or perhaps even a by-pass.

Cardiac catheterization studies revealed a normal heart. Normal blood flow, proper pressures in the ventricle, proper pumping. The cardiologist stated that he estimated the ejection fraction in the 60s just by watching how the heart pumped the contrast dye.

Well, if this had been done in a fee for service situation I would be thinking that I had been led down the primrose path and improperly relieved of my money.

As it happens, this work was done by an HMO who's docs are salaried. Hence, no motive for churning.

Also, my personal take on the docs involved is positive. I like them and believe that they are in fact competent.

My question....Does this sort of thing happen with some regularity, or was this a very odd or unusual set of events?

Very true. Many years ago I had a sonogram test that showed a shadow and the interpretation was possible cancer. I was sent to a surgeon who advised surgery because I had gallstones and they then could find out if there was cancer. I wanted a second sonogram test because I had suspicion about the person giving me the sonogram - just a gut feeling. I was refused a second sonogram test but I insisted that some other test be done. They agreed to give me a CT scan. The CT scan did not show any shadow or possibility of cancer. I again asked for a second sonogram test to be done by a different technician and they agreed. The second sonogram test showed no shadow and did not indicate any possibility of cancer.

Sometimes you have to play physician yourself.

We know our bodies better than they do. I offered to bet the young doctor a weeks wages that my arteries were ok. He would not take the bet.

In this case frankly, it is very unlikely that cost cutting had anything to do with the outcome. The HMO involved is a first rate organization with an outstanding reputation. They have served me and my family very well for fifteen years. Nor, do I think that anything was done wrong. On the contrary, they were quite willing to double check initial Cardiolite results with the dobutamine-echo.
No, this is just one of those things that happen from time to time, and I'm not angry or upset.

My question simply was and still is, how common is such a series of events.
I'd like to know the approximate (guestimated) frequency with which two different forms of positive stress tests both turn out to be in error.

Or perhaps more generally, what are the individual rates (probability) of false positives per test--e.g. .15 for each would leave the chance of a double false positive at .0225.

That 2% is quite a financial drain (on idividuals and insurance companies)
when one considers all of the costs of a cath study.

What might be done to cut this rate in half?
See where I'm going?

(I can understand how machine errors could produce a false positive for cardiolite. I don't understand how wall motion studies can go awry. Is it possible that the interpreters see what they are expecting to see? If so, how can this be remedied. Could error rates be reduced if the order or testing were reversed? )