What Are Adenosine Stress Tests?

Adenosine stress tests, also known as adenosine nuclear stress tests, are a diagnostic tool used to observe the heart under stress. These tests are usually ordered when a doctor feels that a patient may have a heart irregularity that affects blood flow. Doctors may order adenosine stress tests if the patient is unable to undergo an exercise stress test for any reason. It is important to follow all precautions when preparing for adenosine stress tests in order to avoid distorting test results.

A doctor may order a stress test for many different reasons. In some cases, stress tests may simply be given as part of a full physical check-up. Doctors may also request the test if a patient has a personal or family history of heart problems, has symptoms that may indicate heart trouble, or if an irregularity is detected during a basic medical examination.

When a stress test is required, doctors may choose to have patients undergo an exercise-based test. This type of test requires the patient to walk or run on a treadmill while attached to heart monitoring devices, in order to see how the heart responds to exertion. If a patient cannot walk on a treadmill due to illness, injury, or other conditions, adenosine stress tests may be ordered instead. Unlike exercise tests, adenosine tests simulate the effects of exertion on the heart using a drug called adenosine.

During the test, the patient will usually be asked to lie on a table while a special camera, called a gamma camera, takes initial pictures of the heart. After these images are recorded, the patient is given intravenous injections of adenosine and a slightly radioactive isotope. The adenosine quickly begins to simulate cardiovascular stress, while the isotope makes it possible for the gamma camera to record images of blood flow in and around the heart. Some patients may feel slightly uncomfortable during the test; common side effects from the adenosine may include chest pain and labored breathing. A doctor or technician will usually stay in the room throughout the test, and should be consulted if side effects become severe.

Proper preparations for adenosine stress tests are important, as certain activities can affect the accuracy of the test. Most of the time, patients are not allowed to eat or drink six hours prior to the test; it may help to schedule the test first thing in the morning to avoid going a long time without food. Caffeine must be avoided for a full 24 hours before the test, as this can skew results. A patient must also consult the doctor about all current medications and follow instructions about skipping any doses.