June 28, 2016
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Coronary Artery Disease Screening Tests (CAD) (cont.)

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Exercise cardiac stress test (treadmill stress test or ECST)

Exercise cardiac stress testing (ECST) is the most widely used cardiac stress test. The patient exercises on a treadmill according to a standardized protocol, with progressive increases in the speed and elevation of the treadmill (typically changing at three minute intervals). During the ECST, the patient's electrocardiogram (EKG), heart rate, heart rhythm, and blood pressure are continuously monitored. If a coronary arterial blockage results in decreased blood flow to a part of the heart during exercise, certain changes (for example, ST segment depressions) may be observed in the EKG, as well as in the response of the heart rate and blood pressure.

The accuracy of the ECST in predicting significant CAD is variable, depending in part on the "pre-test likelihood" of CAD (also known as Bayes' theorem). In a patient at high risk for CAD (for example, advanced age, multiple coronary risk factors), an abnormal ECST is very predictive of the presence of CAD (over 90% accurate). However, a relatively normal ECST may not reflect the absence of significant disease in a patient with the same risk factors. Conversely, in a low-risk patient, a normal ECST is very predictive of the absence of significant CAD (over 90% accurate), but an abnormal test may not reflect the true presence of CAD (so-called "false-positive ECST"). The ECST may either miss the presence of significant CAD, or be a false-positive test, due to a variety of cardiac circumstances, which may include:

  1. An abnormal EKG at rest, which may be due to abnormal serum electrolytes, abnormal cardiac electrical conduction, or certain medications, such as digitalis;
  2. Heart conditions not related to CAD, such as mitral valve prolapse or hypertrophy (increased size) of the heart; or
  3. An inadequate increase in the heart rate and/or blood pressure during exercise.

What if the initial ECST does not clarify the diagnosis?

When the doctor determines that the results of the ECST do not accurately reflect the presence or absence of significant CAD, additional tests are often used to clarify the condition. These additional options include radionuclide isotope injection and ultrasound of the heart (stress echocardiography) during the stress test.

Medically Reviewed by a Doctor on 5/29/2015

Source: MedicineNet.com

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