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Question:
Should I be concerned about the accuracy of my stress test?
I am a male, 49 years old, rather sedentary (3 -4 times a week 30 min. brisk walks), 5'10", 230 lbs. I recently had a stress test in conjunction with nuclear imaging. The test went fine, with no chest pain, and no changes on ECG. The imaging revealed a reversible defect, meaning at rest all was fine, at stress parts of the heart were not getting as much blood. There was no sign of infarction. I had some concerns about the way the test was conducted.
The concerns are:
1) The stress portion of the test was done after a sleepless night (really sleepless as in not closing an eye), not a sip of water for past 12 hours, edgy from all worries from what could be wrong with my heart to what effect the radioactive agent might have on my body.
2) The stress was conducted to Heart Rate of 173 bpm. My understanding was that the test was to be conducted to (220-49)*.85=145 bpm. From what I learned, at HR approaching max. even the most conditioned of hearts struggle, thus raising the possibility of false positive.
3) No chest pain, going to HR 173 bpm, more than max. HR for my age (220-49=171), BP 180/100, no depression of ST segments.
My questions are:
1) Do you think this was a physiological ischemia?
2) Do you think this ischemia was brought about by conducting the test to more than my max. HR?
3) Factors like lack of sleep, poor hydration, lack of caffeine (for someone who drinks quite a bit of coffee) do not affect the way the heart performs?
4) Could ischemia show up on the scan because of poor heart conditioning?
submitted by Valentin from Cambridge, ON, Canada on 7/5/2017
Answer:
by Texas Heart Institute cardiologist, Scott R. Sherron, MD 
The physiologic stresses of sleeplessness and lack of caffeine and anxiety certainly put a stress on the body as a whole but have not been specifically associated with false positive MPS (myocardial perfusion study). Measurement of stress images is normally performed between 85 and 100% of predicted maximum, but it is true that the chance of false positive is higher at the highest end of the range. The lack of symptoms is good but only minimally useful since nearly 20% of people with significant coronary lesions (>70% stenosis) will have no symptoms even at max HR. The absence of ECG changes is more reassuring but the incidence of false negative ECG on stress is not a tiny number (approx 5% depending on pretest probability).
In the setting and with the findings you describe, I would certainly want additional testing, but a CCTA is a very reasonable first choice. It is particularly useful when the coronaries are normal or near normal, so it would allow you to avoid an unnecessary invasive procedure. Of course, if there is any significant abnormality, you would likely need invasive evaluation with angiography. The decision to stent a particular coronary lesion will be colored by your absence of symptoms, but detailing the anatomy is a useful tool in planning ongoing therapy and followup.
My recent “poster-child” for this scenario is a 50 yo man with some risk factors but in excellent shape who ran a marathon and then failed an nuclear stress test in my office. Absolutely no symptoms, but at angiography, he was found to have a 90% Left main stenosis. He underwent successful bypass surgery but most certainly would not have survived long term without this therapy. He is an extreme example, but not completely rare.
Hope this helps.
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Updated July 2017
