need an answer for this test please

[stellatj]

Hi thanks for your help i am scheduled to have a thallium stress test called nuclear perfusion my instructions say no coffee or tea or caffaine for 48 hours not even decaf can you please explain why i am gonna go crazy without my coffee. they say they test my heart at rest then i walk the treadmill and they test it again but why no caffaine thanks

[SRBKING]

caffeine is a big no no becuz it increases ur heart rate.  They try to get the most accurate reading of your heart at rest without any stimulants.

[CCF-M.D.-RCJ]

fwilson,

MPHR is Maximum Predicted Heart Rate and is generally calculated as 220-age.

RCJ

[CCF-M.D.-RCJ]

timok,

Great question.

Caffeine is a stimulant, and thus raises the baseline heart rate.  One of the parameters we measure at the Clinic is called "Chronotropic competence (Cc)".  This is calculated as:

Cc = (max heart rate - rest heart rate)/(85% MPHR - rest heart rate).

If the Cc is less than 0.8, then it is abnormal, and thus adversely affects the patient's prognosis.  The higher the resting heart rate, than the more likely the Cc will be abnormal.  Therefore, we ask you to not take any stimulants, such as caffeine, prior to the test.

Hope that helps.