What are the Different Types of Stress?
Stress tests are divided into two categories; exercise and pharmacologic.
Exercise Stress
Exercise tress tests usually involve walking or running on a treadmill. In some cases, a bicycle is used. An exercise stress test sometimes includes imaging of the heart with a nuclear camera or an echocardiography (ultrasound) machine. The imaging takes place before and after stress to allow for a comparison of the resting heart to the one under stress.
Pharmacologic Stress
If you are unable, unwilling, or have a contraindication to exercise stress, pharmacologic stress can be used.
The pharmacologic means of achieving stress include one of three agents; adenosine (Adenoscan), dipyridamole (formerly called Persantine), and dobutamine.
Adenosine and dipyridamole
Both adenosine and dipyridamole dilate the coronary arteries. Normal coronaries dilate better than those with blockages, resulting in different amounts of blood flow to the affected heart muscle. Nuclear imaging can be used to evaluate the amount blood flow to the different areas of the heart and pinpoint areas of blockage.
The test using adenosine or dipyridamole is usually performed with patients lying or sitting. In some people, adenosine and dipyridamole can cause side effects such as chest discomfort and a facial flushing. These symptoms can be decreased by slowly walking on a treadmill during the infusion.
Dobutamine
Dobutamine is a medication that, much like exercise, increases the speed and strength of heart contractions. It¡¯s usually used if patients cannot tolerate exercise stress and have contraindications to adenosine and dipiridamole, such as asthma. This test is performed with patients lying or sitting.
In a Dobutamine stress test the heart is imaged before and after the Dobutamine infusion also allowing for a comparison of the resting and stressed heart.
Sources:
ACC/AHA/ASNC 2003 Guidelines for the Clinical Use of Cardiac Radionuclide Imaging