Also known as a cardiac stress test, this is a standard procedure that measures a heart’s ability to respond to external stress in a controlled environment. During the test, stress is induced through exercise because some patients with coronary artery blockages may have minimal symptoms that are unremarkable at rest during an EKG test. Symptoms of heart disease may become unmasked when the heart is exposed to the stress of exercise.


How does it work?

During exercise, healthy coronary arteries dilate and open larger than an artery that has a blockage. The healthy arteries have to work harder in order to compensate for the reduced flow in blocked arteries. The blocked (or narrowed) arteries that have a lower supply of blood distribution cause the involved muscle to starve during exercise, resulting in uncomfortable symptoms.


Prior to the test, the patient’s heart rate and blood pressure are taken at rest and then electrodes are placed onto the chest, shoulders, and hips. The electrodes transmit data from different areas of the body and record it to an EKG machine. The physician will monitor the EKG and will be able interpret the signals as the test is going on.  


When is a stress test needed?

Treadmill stress tests are generally ordered by a physician who suspects coronary artery disease (CAD) as a potential threat. If CAD is not a factor, stress tests may also be performed to evaluate blood pressure response to exercise in patients with hypertension, as well as monitoring exercise tolerance for patients who are experiencing fatigue and shortness of breath.   


Stress tests are heavily dependent on the interpretation of EKG changes produced by exercise and the reliability drops if there are significant EKG changes while at rest. Patients with high blood pressure, cardiac pacemakers, or a presence of bundle branch block pattern could potentially impact the results of an EKG.


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