A dobutamine stress test works by mimicking the heart's response to exercise without the need for physical exertion. This test is done by administering a drug called dobutamine to increase the heart rate. Another compound called Cardiolite® is also often administered during the test to help create clear images of the coronary arteries. Two sets of images are taken during the test: a set to show the heart's response during the resting phase and a second set to show the heart's response during the stress phase. A dobutamine stress test can be used as a simple, accurate way to discover coronary problems in individuals who are unable to take a treadmill stress test.
Knowing what to expect before a dobutamine stress test can be helpful in preparing for the experience. Depending on whether the dobutamine stress test is performed with an electrocardiogram (EKG) or nuclear imaging, the test can take anywhere from one to three or more hours to complete. The doctor will most likely provide a list of guidelines to follow on the day of the test. These may include instructions to fast before the test and to avoid caffeine and cigarettes, both of which can cause problems with testing.
The dobutamine stress test does not require physical exertion, so most of the test takes place while sitting or lying down. If a dobutamine stress electrocardiogram is to be performed, an EKG monitor is used to track the patient's heart rate, beginning with a resting reading. Blood pressure readings are taken, and an echocardiogram is often performed to get a look at the patient's heart before the stress test itself.
In a nuclear dobutamine stress test, Cardiolite®, also known as sestamibi, is injected and images are taken with a gamma camera. Cardiolite® contains trace amounts of radioactive material to make the coronary arteries visible in the images. Each time it is administered, it needs at least 30 minutes to circulate through the body.
After the resting images are taken, dobutamine is injected into the vein via an intravenous (IV) line. This takes about 12 to 15 minutes, and additional Cardiolite® may be injected immediately after. The dobutamine raises the patient's heart rate, providing a response similar to exercise. In both nuclear and electrocardiogram tests, an EKG is used to monitor the patient as the dobutamine is administered.
In addition to increased heart rate, other side effects such as headache, dizziness, and shortness of breath may occur during a dobutamine stress test. While these reactions are usually normal, they should be reported to lab personnel, as they could indicate a serious problem. The patient should be monitored during the entire process, and medication can be stopped should unexpected side effects occur.
Each set of images — resting and stressed — take about 15 minutes to perform. When the images are taken, the patient is usually asked to lie still with the left arm raised above the head. This allows the camera or ultrasound transducer, depending on the test, to take the needed images. After the test is complete, patients are usually monitored until the heart rate and blood pressure have returned to normal.