Many people think that a stress test measures the amount of stress that you are under. However, it is important from the start to point out that a stress test does not do this. What the stress test measures is the blood flow to and from the heart during stress ( exercise ) and at rest.
Examining coronary artery disease can be difficult when the heart is at rest.The stress test is a diagnostic tool that doctors use to gather more information on coronary artery flow when the stress placed on the heart is increased.
Typically this type of test is done on a treadmill. The gradient of the treadmill gradient and speed of the treadmill is adjusted according to protocol until the patient achieves their target heart rate, which is usually 85 percent of their maximum heart rate.
Sometimes more information is required by the doctor than a regular cardiac test can give. If this is the case your physician may order a nuclear stress test.
This involves the intravenous injection of an isotope which allows the blood flow around the heart to be captured by various imaging techniques.
The blood flow from around the heart is compared at rest and following exercise , and is also compared to a bank or ordinary cases. This diagnostic tool gives the doctor more information that an ordinary test.
Sometimes the patient is unable to walk on a treadmill or to get their heart rate up to the required level. Back problems, dizziness, and poor gait and posture may mean that they have trouble walking on a treadmill to stimulate their heart.
In this case a chemical test may be ordered by the treating doctor. In this type of test medication is also be used. Medication such as dipyridamole or adenosine may be given intravenously to stimulate the heart in a similar way as the exercise would.
The patient is then monitored on an electrocardiogram (ECG) and blood pressure machine.
Why would you want a stress test
If you have symptoms of coronary artery disease or factors that put you into a significantly high risk category then a stress test may be ordered. If you have unexplained shortness of breath or fatigue or high blood pressure then a test could also be ordered.
Reliability and accuracy ot the test
The American Heart Association suggests that the cardiac stress test is able to diagnose two thirds of patients with having coronary artery disease. This 67 percent reliability can be increased up to about 85% with a nuclear stress test which takes images of the heart at rest and following exercise.
A positive stress test result is likely to influence your doctor for treatment. A positive stress test could indicate a high risk of coronary artery disease and your doctor is likely to recommend lifestyle changes that include healthy eating and moderate and regular exercise.
But even with a negative stress test result it is always a good idea to start thinking about lifestyle changes that result in you living healthy.
Dr Kell works as a stress management consultant. He writes more about the procedures of different types of stress tests such as the adenosine stress test and the nuclear stress test