A chemical stress test is a clinical test used to measure the heart's ability to respond to external stress. In this case the controlled 'stress' is chemical in nature, and is a relatively new method of testing cardiac strength – the more traditional cardiac stress test using treadmills in order to place physical stress on the individual in question.
How it Works
Here the chemical used is an isotope medication (commonly dipyridamole, dobutamine or adenosine) that is delivered intravenously. This then places stress on the heart by causing the arteries to dilate – meaning that the blood flows at maximum volume and the heart has to work harder to pump it around (imagine drinking through a thin straw versus trying to suck water through a very wide straw). The entire process only lasts around six minutes, during which the patient is hooked up to an EKG machine that is used to monitor their heart rate throughout.
In preparation for the chemical stress test the patient will usually be asked to abstain from food and drink around six hours prior. They might also need to stop certain medications and supplements three days prior to the examination to ensure that there are no interactions (some medications work by thinning the blood which can increase the impact of the stress test).
While physicians generally prefer the old-fashioned treadmill test when available, there are certain circumstances in which this is not a tenable option and chemical stress test is the only way to test the strength of the heart. The reason for this may for instance be that the patient is too unhealthy in other ways to push themselves on the treadmill – perhaps due to a limb injury, breathing conditions or a lack of energy. At the same time some patients may be scared or put off by the idea of running on a treadmill.
However while a chemical stress doesn't require the patient to do anything and only lasts six minutes, it can have some nasty short term side effects including a burning and tingling sensation throughout the body, sweats, migraines, vomiting and nausea. The headache may persist following the test. In rare cases this test could induce a heart attack, though that is a risk with any cardiac stress test.
Like the treadmill stress test, the chemical stress test has a 10% margin for error, and so it will normally be used in conjunction with other tests.