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Nuclear Test (Thallium Stress Test)

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Thallium Stress Test

WHAT IS THALLIUM STRESS TEST?

A thallium stress test can also be called the “nuclear scan” because a radioactive material is utilized when performing the test. It can also be called a radionuclide imaging or myocardial perfusion scan.

Therefore, a thallium stress test is said to be a nuclear test conducted on a patient to indicate the flow rate of blood into the heart when the patient is exercising and resting. Little quantity of radioactive material called the “Radionuclide” or “Thallium” is used to perform this test. It helps in determining regions in the heart where the flow of blood is limited while exercising similar to chemical stress and exercise stress tests.

WHY IS IT DONE?

The thallium stress test is performed majorly to diagnose conditions acquainted with the heart by providing information such as:

  1. Pump rate of blood into the heart.
  2. Damages around the heart region.
  3. Stoppage of the flow of blood through the arteries to the heart.
  4. Size of the chambers of the heart.
  5. Regions in the heart lacking blood and oxygen.
  6. History of possible heart attack and the area of occurrence. 
  7. Monitoring of heat treatment. 

Other minor  reasons why the thallium stress test is done are listed below:

  1. Pains in the chest region.
  2. Effectiveness of medications administered.
  3. The success rate of surgery.The healthy state of the heart.

ELIGIBILITY:

The thallium test can be performed on anyone without constraints to angina or any cardiac disease as some substances present in the usage of the test can result in a heart attack. 

Though some instructions can be given by the doctor for possible success. Therefore, patients without these diseases can undergo the thallium stress test as long as they feel any signs and symptoms relating to a heart condition. 

HOW TO PREPARE

It is required of the patient to put on a comfortable outfit that can be used for exercising alongside shoes recommended for jogging. 

It is recommended that the patient is to restrict food intake or water after midnight of the day the thallium stress test is to be performed. Then, the patient should avoid drinking liquids with caffeine present in them including painkillers and chocolates within a 24 hours range just before the test.

Medications for angina and asthmatic patients may be avoided too depending on the doctor’s prescription as such drugs tend to influence the final results when the thallium stress test is performed. 

Patients utilizing defibrillators or pacemakers must inform the doctor alongside patients with diabetes to be instructed with the amount of insulin to take before the test. 

A diabetic patient can not stay too long without eating so it is recommended that they take light food just 4 hours before the test is performed. 

Persons who have taken pills for enhancing sexual drive such as viagra or tadalafil within 24 hours before the test must relate the information to the doctor. Female patients with the possibility of pregnancy or are breastfeeding must report the situation to the doctor. Then, a consent form must be signed proving the permission of the patient to undergo the test.

Lastly, smoking within the four hours before the diagnostic test is carried out is highly restricted.

PROCESS

The thallium stress test is conducted in a hospital mainly a doctor’s office. Firstly, the specialist injects the intravenous needle (IV) inside the elbow and the radioisotope is injected through the intravenous line. This radioisotope is nuclear material and it tends to indicate the flow of blood which is signified by the gamma camera.

The thallium stress test is performed in two phases: “the resting phase” and “the exercising phase” where the heart is captured with the aid of the gamma camera to monitor the flow of blood for both phases. An injection will be administered to the patient before each of the phases and the doctor decides which of the phases comes first. 

The two phases are explained below:

  • Resting Phase

The test is easy to conduct while the patient is at rest. For this phase, the patient is expected to lay down for a period of 15 to 45 minutes and the radioisotope flows through the body to the heart. 

Afterward, the patient is taken to the exam table and hands will be placed above the head then the gamma camera photographs the patient consecutively, monitoring the flow of blood.

  • Exercising Phase

In this phase, a treadmill is mostly used where the patient will be required to jog slowly at first before increasing the speed gradually. 

The blood pressure and heartbeat will be monitored strictly as the exercise is ongoing for about 30 minutes before stopping. Then, the patient is laid again down on the examination table. Then, the blood flow into the heart is monitored by the gamma camera, and pictures are taken. These pictures are compared with the previous pictures taken while at rest to deduct the state of blood flow.

RESULTS

The output from the thallium stress test is dependent on the objectives of the test. The age of the patient also affects the result. The results are grouped into:

  • Normal Result

When the flow rate of blood into the heart is stable then the patient is normal.

  • Abnormal Result

This shows the immoderate flow of blood into the coronary arteries resulting from the blockage of some arteries. Also, it may show scars from a previous heart attack, disease of the heart, or even a large heart. When diagnosed with a heart condition, it is necessary to undergo further testing to proffer treatment programs to aid recovery.

RISKS

The thallium test is not a painful process as when the intravenous needle is injected, just a sting is felt accompanied by a feeling of warmth. Also, the radioisotope can be urinated out.

Like some tests, there are complications involved in performing the test ranging from normal complications to radiation risks. These complications are listed below:

  1. Possibility of reacting to the radiation dye.
  2. Dizziness resulting in a reduction in blood pressure caused by exercise.
  3. Possible arrhythmias or irregular heartbeat.
  4. Pain in the chest region.
  5. Minor headache.
  6. Breathing issue.
  7. Patient being anxious.
  8. Trembling.
  9. Skin rash.

Also, patients with angina or cardiac diseases are not permitted to use drugs such as the “Lexiscan” and “Adenoscan” according to the Food and Drug Administration (FDA) and these drugs are present during the test. The drugs tend to make blood overflow into areas that are unobstructed leaving the areas with issue blood-free which could result in a heart attack.

WHO PERFORMS THE TEST?

A doctor can easily perform the test alongside a nurse. Though, a radioactive therapist or a professional therapist can also perform this procedure.

DURATION

The thallium stress test normally takes 3 to 4 hours due to running the test with and without exercising. The test is done once when the result indicates a healthy heart but if the patient is diagnosed with a heart condition, more tests will be performed. The duration for the output of the result is always small. The doctor can give the result immediately.

COST

In the U.S, thallium stress test costs between $900 to $3000. Since there is no universal fixed cost, different countries and hospitals can charge differently.

FAQs

  • What should be avoided after the nuclear stress test?

It is required to abstain from drinks containing caffeine or soda such as mountain dew for 3 days after undergoing the thallium stress test.

  • How long does it take for the radioactive substance to leave the body?

The radioisotope is excreted through the urine so it takes an average of 60 hours after the test to completely excrete the radioactive substance.

  • Can the nuclear stress test damage the heart?

On a normal basis, the nuclear stress test can not affect the heart except for patients diagnosed with angina or cardiac diseases. The chances of having a heart attack are feasible in this case if the patient with angina does not follow the instructions provided by the doctor before the test.

  • Can you pass the thallium stress test and still have a blockage?

Yes, the thallium stress test accounts for blockages ranging from 70% and above, therefore, if the percentage of the blockage is minimal, it might not be detected but it does not rule out the chances of a future heart attack. So, it is possible to pass the test and have a little blockage.

  • Why do they make the throat numb before the test?

The patient is always injected with sedatives and anesthesia is administered to make the patient comfortable and experience no pain during the process.

  • How accurate is the thallium stress test?

The thallium stress test is known to be the most accurate stress test with an accuracy rate of 81% while the remaining rate accounts for blockages.

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