Diagnostic Testing: Difference between revisions
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==Cardiac stress test== | ==Cardiac stress test== | ||
[[Image:Stress_test.jpg|thumb|300px|'''Figure 10.''' Cardiac stress test making use of a walking treadmill. Source: Wikimedia public domain.]] | [[Image:Stress_test.jpg|thumb|300px|thumb|'''Figure 10.''' Cardiac stress test making use of a walking treadmill. Source: Wikimedia public domain.]] | ||
Cardiac stress tests compare the coronary circulation while the patient is at rest with the same patient's circulation observed during maximum physical exertion, showing any abnormal blood flow to the heart's muscle tissue (the myocardium). This test can be used to diagnose ischemic heart disease, and for patient prognosis after a heart attack (myocardial infarction). | |||
The level of mechanical stress is progressively increased by adjusting the difficulty (steepness of the slope) and speed. The test administrator or attending physician examines the symptoms and blood pressure response. With use of ECG, the test is most commonly called a cardiac stress test, but is known by other names, such as exercise testing, stress testing treadmills, exercise tolerance test, stress test or stress test ECG. | The level of mechanical stress is progressively increased by adjusting the difficulty (steepness of the slope) and speed. The test administrator or attending physician examines the symptoms and blood pressure response. With use of ECG, the test is most commonly called a cardiac stress test, but is known by other names, such as exercise testing, stress testing treadmills, exercise tolerance test, stress test or stress test ECG. | ||
=== | ===Indication=== | ||
[[Image:StressECG STDepression.jpg|thumb|right|300px|Stress-ECG of a patient with coronary heart disease: ST-segment depression (arrow) at 100 watts of exercise. A: at rest, B: at 75 watts, C: at 100 watts, D: at 125 watts.]] | [[Image:StressECG STDepression.jpg|thumb|right|300px|Stress-ECG of a patient with coronary heart disease: ST-segment depression (arrow) at 100 watts of exercise. A: at rest, B: at 75 watts, C: at 100 watts, D: at 125 watts.]] | ||
The American Heart Association recommends ECG treadmill testing as the first choice for patients with medium risk of coronary heart disease according to risk factors of smoking, family history of coronary artery stenosis, hypertension, diabetes and high cholesterol. | The American Heart Association recommends ECG treadmill testing as the first choice for patients with medium risk of coronary heart disease according to risk factors of smoking, family history of coronary artery stenosis, hypertension, diabetes and high cholesterol. | ||
===Diagnostic value=== | ===Diagnostic value=== | ||
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(Sensitivity is the percentage of sick people who are correctly identified as having the condition. Specificity indicates the percentage of healthy people who are correctly identified as not having the condition.) | (Sensitivity is the percentage of sick people who are correctly identified as having the condition. Specificity indicates the percentage of healthy people who are correctly identified as not having the condition.) | ||
The value of stress tests has always been recognized as limited in assessing | The value of stress tests has always been recognized as limited in assessing coronary atherosclerosis. This is because the stress test has a relatively high false-negative and false-positive rate. Other detection methods have higher sensitivity and specificity but this improved test characteristics often comes at a price, either in the form of radiation (CT), risk of complications in an invasive procedure (coronary angiography), or costs and limited availability (MRI). | ||
===Contraindications=== | ===Contraindications=== | ||
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*Adenosine and dipyridamole can cause mild hypotension. | *Adenosine and dipyridamole can cause mild hypotension. | ||
*As the tracers used for this test are carcinogenic, frequent use of these tests carries a small risk of cancer. | *As the tracers used for this test are carcinogenic, frequent use of these tests carries a small risk of cancer. | ||
===Limitations=== | ===Limitations=== |