Nuclear Stress Test

One of the nuclear medicine procedures that is used as a diagnostic tool is called the nuclear stress test. It is also called myocardial perfusion imaging, thallium stress test, and cardiolite stress test.

The test involves injecting a small amount of 'radionuclide', a radioactive substance, into the heart to monitor the blood flow to the heart muscles both at rest and during stress. The nuclear scanning helps produce an image of the heart muscles and the blood flow through it.

The test is usually performed along with exercise using a treadmill; however, patients who cannot exercise due to paralysis, heart illnesses, breathing difficulties, etc., can undergo the chemical stress test.

It is carried out using intravenous drugs when the patient is resting as well as under stress. A patient may be required to work on a treadmill to stimulate stress. If the patient is unable to do so, he may be given certain drugs to stimulate the effects of exercising.

 Thus, there are two types of cardiac stress test procedures:

• Nuclear stress test procedure with exercise
• Chemical stress test

With Exercise
This stress test is used to find out the areas within the heart muscle that receive decreased blood flow during exercise. A tiny amount of radionuclide, either thallium or technetium is injected into the body through intravenous catheter. The intravenous catheter is placed into a vein in the arm or hand.

Once the radionuclide is injected and circulated through the body, pictures of the heart are taken while the patient is at rest. The patient is asked to lie down on a table and using a gamma camera, pictures of the heart are taken. This type of scan is called the rest scan of the heart. This gamma camera scanning takes about 15 to 20 minutes.

Once this process is completed, the patient is asked to walk on a treadmill. When the patient has achieved maximum stress level, he is injected with a second radionuclide injection using an intravenous catheter. Once the radionuclide is assumed to have circulated throughout the body, a second gamma camera scan is performed. This is called the stress scan of the heart, that too lasts for just about 15 to 20 minutes.

The aim of this test is to determine the partially or fully blocked arteries of the heart. These spots will be observed as 'cold spots' or 'defects' in the scan as they fail to absorb the radionuclide.

Chemical Stress Test
When the patient is unable to exercise on a treadmill, the doctor may suggest chemical stress test. The patient is given medications that help dilate the coronary arteries and increase the heart rate. Thus, creating an effect similar to stress due to exercise.

A radionuclide, thallium or technetium, is injected into the patient's body through an intravenous catheter, which is placed in the vein of the arm or hand when the patient is at rest. After the radionuclide circulates through the blood stream, gamma camera is used to take pictures of the heart. The patient is asked to lie still on a table, and the scanning takes about 15 to 20 minutes. This is known as the rest scan of the heart.

The stress scan of the heart is performed by giving medications to the patient to increase the heart rate. When the patient is at the peak of stress, he is given a second dose of the radionuclide through a catheter. Once the radionuclide circulates through the blood, a second gamma camera scan is performed. This too takes about 15 to 20 minutes.

The chemical stress test too helps detect any 'cold spots' or 'defects' within the arteries that are unable to absorb the radionuclide due to partial or full blockage.

It is a very safe procedure that is mostly free from any kind of complications. However, in rarest of the rare cases, there may be some side effects.

 The complications that may arise are as follows:

• Allergic Reaction: There is a rare possibility that a person may be allergic to the radioactive dye that is injected into the arm during the procedure.
• Low Blood Pressure: While exercising on the treadmill, a person may experience low blood pressure and feel dizzy or faint.

• Arrhythmia: A patient may experience arrhythmia or abnormal heart rhythms during an exercise stress test.
• Chest Pain: The medications may cause chest pain due to the stress on the heart. This pain is usually brief and disappears soon. This pain is usually brief and will disappear soon.

• Heart Attack: This is a very rare possibility that a patient may suffer heart attack due to the stress caused during the exercise.

The temporary side effects may include:

• Nausea
• Vomiting
• Headache
• Excessive sweating
• Chest pain
• Tingling sensation all over the body
• Flushing
• Dizzy spells
• Anxiety or panic attack

If you experience excessive perspiration, shortness of breath, lightheadedness, chest pain, jaw pain, or any kind of discomfort, inform your doctor about it immediately. An echo stress test is monitored using an ECG monitor to detect any signs that suggest the test to be halted immediately.

The cost of the test is about USD 2,000 to USD 3,000. If one is to undergo this test, make sure not to have coffee, tea, other caffeinated beverages, chocolates, colas, and even decaffeinated coffee for about 12 to 24 hours before the test. Medications used to treat asthma and angina may interfere with test results. Therefore, consult your doctor if you need to stop taking any medicines before the test.

Disclaimer: This story is for informative purposes only, and should not be used as a replacement for expert medical advice.