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Diagnostic Testing: Difference between revisions
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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. | ||
== | ===Function=== | ||
== | |||
[[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.]] | ||
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*Intracoronary ultrasound or angiogram can provide more information at the risk of complications associated with cardiac catheterization. | *Intracoronary ultrasound or angiogram can provide more information at the risk of complications associated with cardiac catheterization. | ||
==Diagnostic value== | ===Diagnostic value=== | ||
The common approach for stress testing by American College of Cardiology and American Heart Association indicates the following:<cite>Two</cite> | The common approach for stress testing by American College of Cardiology and American Heart Association indicates the following:<cite>Two</cite> | ||
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The anatomic methods directly measure some aspects of the actual process of atherosclerosis itself and therefore offer the possibility of early diagnosis, but are often more expensive and may be invasive (in the case of IVUS, for example). The physiological methods are often less expensive and more secure, but are not able to quantify the current status of the disease or directly track progression. | The anatomic methods directly measure some aspects of the actual process of atherosclerosis itself and therefore offer the possibility of early diagnosis, but are often more expensive and may be invasive (in the case of IVUS, for example). The physiological methods are often less expensive and more secure, but are not able to quantify the current status of the disease or directly track progression. | ||
==Contraindications== | ===Contraindications=== | ||
Stress cardiac imaging is not recommended for asymptomatic, low-risk patients as part of their routine care.<cite>Three</cite> Some estimates show that such screening accounts for 45% of cardiac stress imaging, and evidence does not show that this results in better outcomes for patients.<cite>Three</cite> Unless high-risk markers are present, such as diabetes in patients aged over 40, peripheral arterial disease; or a risk of coronary heart disease greater than 2 percent yearly, most health societies do not recommend the test as a routine procedure.<cite>Three</cite><cite>Four</cite><cite>Five</cite><cite>Six</cite> | Stress cardiac imaging is not recommended for asymptomatic, low-risk patients as part of their routine care.<cite>Three</cite> Some estimates show that such screening accounts for 45% of cardiac stress imaging, and evidence does not show that this results in better outcomes for patients.<cite>Three</cite> Unless high-risk markers are present, such as diabetes in patients aged over 40, peripheral arterial disease; or a risk of coronary heart disease greater than 2 percent yearly, most health societies do not recommend the test as a routine procedure.<cite>Three</cite><cite>Four</cite><cite>Five</cite><cite>Six</cite> | ||
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*Acutely ill for any reason<cite>Seven</cite> | *Acutely ill for any reason<cite>Seven</cite> | ||
==Adverse effects== | ===Adverse effects=== | ||
Side effects from cardiac stress testing may include | Side effects from cardiac stress testing may include | ||
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*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. | ||
==Pharmacological agents== | ===Pharmacological agents=== | ||
The choice of pharmacologic stress agents used in the test depends on factors such as potential drug interactions with other treatments and concomitant diseases. | The choice of pharmacologic stress agents used in the test depends on factors such as potential drug interactions with other treatments and concomitant diseases. | ||
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Aminophylline may be used to attenuate severe and/or persistent adverse reactions to Adenosine and Lexiscan. | Aminophylline may be used to attenuate severe and/or persistent adverse reactions to Adenosine and Lexiscan. | ||
==Limitations== | ===Limitations=== | ||
The stress test does not detect: | The stress test does not detect: | ||
*Atheroma | *Atheroma | ||
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The test has relatively high rates of false positives and false negatives compared with other clinical tests. | The test has relatively high rates of false positives and false negatives compared with other clinical tests. | ||
==Results== | ===Results=== | ||
Once the stress test is completed, the patient generally is advised to not suddenly stop activity, but to slowly decrease the intensity of the exercise over the course of several minutes. | Once the stress test is completed, the patient generally is advised to not suddenly stop activity, but to slowly decrease the intensity of the exercise over the course of several minutes. | ||
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*Unstable atheroma produces ''vulnerable plaques'' hidden within the walls of coronary arteries which go undetected by this test. | *Unstable atheroma produces ''vulnerable plaques'' hidden within the walls of coronary arteries which go undetected by this test. | ||
*Limitation in blood flow to the left ventricle can lead to recurrent angina pectoris. | *Limitation in blood flow to the left ventricle can lead to recurrent angina pectoris. | ||
==Stress echocardiography== | |||
A stress test may be accompanied by echocardiography.<cite>One</cite> The echocardiography is performed both before and after the exercise so that structural differences can be compared. | |||
==Nuclear stress test== | |||
The best known example is myocardial perfusion imaging. Typically, a radiotracer (Tc-99 sestamibi, Myoview or Thallous Chloride 201) may be injected during the test. After a suitable waiting period to ensure proper distribution of the radiotracer, photos are taken with a gamma camera to capture images of the blood flow. Photos taken before and after exercise are examined to assess the state of the coronary arteries of the patient. | |||
Showing the relative amounts of radioisotope within the heart muscle, the nuclear stress tests more accurately identify regional areas of reduced blood flow. | |||
Stress and potential cardiac damage from exercise during the test is a problem in patients with ECG abnormalities at rest or in patients with severe motor disability. Pharmacological stimulation from vasodilators such as dipyridamole or adenosine, or positive chronotropic agents such as dobutamine can be used. Testing personnel can include a cardiac radiologist, a nuclear medicine physician,a nuclear medicine technologist, a cardiology technologist, a cardiologist, and/or a nurse. | |||
==References== | ==References== | ||