What is a Chemical Stress Test for a Heart?

Even though exercise stress tests are not very harmful, these tests are sometimes not the optimum measures that can be carried out to test the condition of the patient's heart. Patients with arthritis and previous heart conditions cannot always endure to perform the exercise stress test. For such patients, the doctors often recommend chemical stress test or a chemical nuclear stress test. With the help of medications, the heartbeat rate is slowly increased and the arteries are dilated. Therefore the body response will be similar to what it would have been during an exercise stress test.

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In the chemical stress test, while the patient is in resting condition, a radionuclide is injected in his or her arm or hand. Soon the radionuclide starts to travel and circulate through the bloodstream. During the process of circulation, the gamma camera captures several pictures of the heart of the patient who is lying motionless during the chemical stress test are going on. This is called as rest scan (similar to recording readings of the heart resting condition during an exercise stress test). Slowly the heartbeat rate increases. The doctor monitors and administers the medication's performance in speeding up the heart rate or dilating the arteries.

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In the chemical stress test, the patient is again injected with a radionuclide when the heartbeat rate reaches at its peak. The similar process of capturing pictures of the heart with the gamma camera goes on. This part of the procedure is referred as stress scan (similar to the readings that are achieved when a patient undergoes the increasing difficulty level of the exercise stress test). Like an exercise stress test, here also any kind of blocked or partially blocked arteries will appear as cold spots. To gain a complete picture, the results can be superimposed with a CT scan or a MRI.

How to Prepare for a Chemical Stress Test?

To prepare for a chemical stress test:

  • The patient should be having an empty stomach since the midnight before the chemical stress test day. Any kinds of caffeinated drinks like coffee, tea and sodas should be avoided. Avoid any kind of painkillers and chocolate that contains caffeine for 24 hours before the chemical stress test day.
  • If you under any kind of medication for asthma, ask your doctor if you can have them before the test since such medications may alter the chemical stress test results. Also if you are taking medications for erectile dysfunction like Viagra, talk to your doctor about whether you are allowed to take them the day before the chemical stress test. You must carry your inhaler during the chemical stress test.
  • If you are on a dosage of insulin or on any medication for diabetes, inform your physician.
  • Your physician should know if you have a defibrillator or a pacemaker.
  • If you are diabetic, it would be not safe for you to fast for so long hours therefore it is suggested that you take very small meals four hours before the test.
  • Update your doctor if you are pregnant or if you are breastfeeding.

What Do the Results of the Chemical Stress Test for Heart Say?

  • If your blood flow is normal and you heart is functioning well then you do not need to continue with any further chemical stress tests and you are not suffering from coronary artery disease.
  • If your heart pumps blood normally at rest but functions abnormally in stress, then you are suffering from coronary artery disease and coronary angiography needs to be done.
  • If the blood flow is not normal at all, it indicates severe coronary artery disease and that you are prone to heart attack. This will recommend for coronary artery bypass, balloon angioplasty or stent replacement
  • If the radionuclide fails to show certain portions of the heart, it means there are damaged or scarred tissues and injuries.
Pramod Kerkar

Written, Edited or Reviewed By:

, MD,FFARCSI

Pain Assist Inc.

Last Modified On: September 23, 2017

This article does not provide medical advice. See disclaimer

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