A reader asks me the following question:
I’m 35 years old male and was positive for myocardial ischemia during stress test. The cardiologist said that my result was borderline. I’m not sure what does he meant by “borderline”. Also does it help if I do CAC score since my stress test already came out with positive MI?
First off, to understand what any stress test means we have to know the pre-test probability of disease. For example, in 35 year old males without chest pain the likelihood of any significantly blocked coronary artery is very low. This means that the vast majority of positive or borderline tests in this group are false positives, meaning the test is abnormal but there is no disease.
Even if we add exertional chest pain into the mix the probability of a tightly blocked coronary in a 35 year year old is incredibly low (but there are some congenital coronary anomalies that occur.)
The accuracy of stress tests varies depending on the type. The standard treadmill stress test with ECG monitoring is about 70% sensitive and 70% specific. Adding on a nuclear imaging component improves the sensitivity (it makes it more likely we will pick up a blockage if it is present) to about 85% however, in the real world, the specificity (chance of a false positive) is still quite high. Accuracy varies a lot depending on how good the study is and how good the reader is.
Borderline for either the stress ECG the stress nuclear (or stress echo) means that the test wasn’t clearly abnormal but it wasn’t clearly normal. It is in a grey zone of uncertainty.
Given your low pre-test probability of disease it is highly likely your “borderline” test result is a false positive. Whether anything else needs to be done at this point depends on many factors (some from the stress test) but most importantly, the nature of the symptoms that prompted the investigation in the first place.
If there are no symptoms and you went for more than 9 minutes on the treadmill likely nothing needs to be done.
Would a coronary calcium scan add anything?
A very high score (>let’s say 100 for age 35) would raise substantial concerns that you have a coronary blockage.
A zero score would be expected in your age group and probably wouldn’t change recommendations .
A score of 1 up to let’s say 100 means you have a built up a lot more plaque than normal and should look at aggressive modification of risk factors but likely wouldn’t change other recommendations.
So the CAC might be helpful but most likely it would be a zero and not helpful.