Question:
I've been ordered to undergo a stress thallium test by my cardiologist
because of a slight abnormality that cropped up diring my treadmill
test. The nurse in the cardiac rehab program mentioned that a stress
echocardiogram would provide the same info with no injection of dye.
Other than the fact that the cardiologists practice has the equipment
for a stress thallium is there any reason to prefer one over the
other?
Answer:
let's think about this: the stress thallium uses the principle that thallium is
injected just shortly before the end of the test and then your heart is scanned. Muscle
receiving good blood supply "soaks" up the thallium and muscle that doesn't have good
blood supply doesn't. Muscle area without good blood supply, therefore, shows up as a
"cold" spot on the scan.
The stress echo shows an ultrasound picture of your heart post-exercise. This shows areas
of heart muscle that are not contracting as well, along with other structures such as
valves.
If one postulates that ischemic areas of the heart will NOT contract as well, then one
would presume that the stress echo would give the same data...but I'm not sure that is
true in a precise manner. However, in general, you would get the same kind of
information. I'd suggest that you discuss this matter with your doctor if you have more
precise questions about the test. If the stress thallium is negative, then you can
presume that all areas of your heart are getting good blood flow, within the validity of
this test, which is pretty high (above 90% accuracy, as I recall.). If the test results
end up being abnormal, you may be recommended for a heart catheterization.
The one thing that I cannot answer that perhaps someone else with more knowledge could
address is this: if a blockage is severe enough to impair blood flow to an area of the
heart, will that same area ALWAYS show up on the stress echo as impaired on contractility?
I'd like to hear more discussion on this.
referring to the discussion on stress thallium vs stress echo.
the thallium does NOT measure the amount of blood that the heart is
receiving. It is a measure of the blood flow to the heart. Thus if all the
arteries to the heart are blocked (as in my case) the results can be
textbook perfect. This was the explaination I received when the angiogram
showed two arteries at more than 50% block and one at 90% blocked. My doctor
uses the mybistin (not sure of spelling) which sounds like a combination of
the radioisotop and echo .
Both stress echo and stress thallium have essentially equal diagnostic
capabilities. Which one provides the best results depends entirely on the
skill and experience of the cardiologist. Since your cardiologist has the
stress thallium equipment, it would appear that a stress thallium study would
be preferable. Incidentally, a dye is not injected during this test but the
radioactive substance thallium. Don't worry, it is completely harmless. Of
far greater concern is what will the cardiologist recommend after the stress
thallium test. There is a high probability he will advise you to undergo
angiograms, and this will be followed by an urgent recommendation that your
blocked coronary artery be treated with angioplasty or bypass surgery.
