Chemical / Pharmalogical Stress tests:

• How does it work?
  A chemical stress test combines an intravenous medication with an imaging technique

  • Isotope imaging

  • echocardiogram

In these cases the medication will increase the heart load instead of exercise. When the patient has a blocked artery, the blood flow to a specific area of the heart muscle will be reduced, causing decreased movement in the affected heart muscle segment (as seen in the stress echo), or reduced isotope uptake (as seen in the nuclear scan).

• When is a chemical stress test performed?
  The test of choice is treadmill stress test, because of the physiological effect on the blood pressure and heart rate. However, exercise may not be possible for physical limitation, shortness of breath, etc. in such cases, chemical stress testing is employed.
   

• Types of chemical stress testing:

• Dipyridamole (Persantine) stress test

• Adenosine stress test

• Dobutamine stress test

Since caffeine alter the efficacy of the Persantine and Adenosine stress testing, it is essential that no tea, coffee or caffeine containing beverages be consumed for 24 hours prior to the test.