CAD Testing

Is an exercise stress test a fairly good test for detecting CAD???

[BUTTERFLY2714]

I have had a stress test and an ECG and they both came back positive and showed ischemia and my cardiologist says that I do not have CAD and that they are false positive.  His opinion is based on the fact that I am a 43 years old woman. So I guess that he doesn't think that both tests are reliable.

[ed34]

Very good question and the answer is no.
For example, you could have very bad CAD but have developed lots of collaterals which are the natural bypass vessels which some people form. So, this could ensure the heart obtains enough oxygen during exercise, hiding the fact that CAD exists.
In June 07, I had a totally blocked Left anterior descending but heart muscle in the area was being fed by collaterals. My EKG was normal, my Echo was normal, my exercise tolerance test was no problem and my nuclear scan looked great. The only reason they knew about my CAD was through angioplasty to rectify a blockage in my Obtuse Marginal 1, causing MI.

[ed34]

I have to add though. An exercise stress test is good to see if your heart is receiving enough oxygen. Even though it can be fooled by collaterals, it is a test to see how your heart is coping rather than whether there is disease there.

[erijon]

A stress test is accurate 65% of the time. If you have a exercise stress test along with nuclear profusion testing the accuracy goes up to 85%. More important, the specificity is 97% meaning that 97% of the individuals that have a normal test result have no CAD.

Hope this helps,

Jon

[BUTTERFLY2714]

I have had a stress test and an ECG and they both came back positive and showed ischemia and my cardiologist says that I do not have CAD and that they are false positive.  His opinion is based on the fact that I am a 43 years old woman. So I guess that he doesn't think that both tests are reliable.

[ed34]

"97% of the individuals that have a normal test result have no CAD"

I wonder how they reach that figure? If 97 patients out of 100 have normal results, they will likely not be tested any further and put on medication for any symptoms. How would they ever know if those 97% have CAD if they are not tested any further?

[erijon]

This is done via follow up studies of a control group of individuals that have been given a particular test. They are tracked over time to their end point which would be a cardiac event or death.

[erijon]

The number of cases of heart disease detected with thallium scans is about 20 percent greater than it would be with exercise testing alone. A common tracer used for perfusion scans is radioactive thallium; the term "thallium scan" is therefore often used synonymously with "perfusion scan."


In experienced laboratories, stress perfusion scans are positive in 75 to 90 percent of patients with anatomically significant coronary disease and in 20 to 30 percent of those without it (false positive).

[heartfluttersflyawayplz]

thats good to know i had one last year and they said all clear, but i was told the stress test only shows it you have a blockage of 70 or above is this so.  

[ed34]

Yes that would be the case because the arteries in the heart are much wider than they need to be. It's only when the arteries are blocked to a stage where blood flow is restricted that you would see a problem. My cardiologist believes that 50% and over can give signs of restriction.

[BUTTERFLY2714]

Should I then believe that I had a false positive on both the ECG and the stress test? They were both done at different clinics about one month and half apart.

[ed34]

I think you should accept the results and continue on any medication and advise they offer. You have to go by your symptoms. If you have a 50-60% blockage it is unlikely they will do anything anyway. They only intervene at 70%. If you have a 50% blockage and no symptoms, then there is no point in treatment, just lifestyle changes but this is something everyone should be doing for the better anyway.