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The nuclear stress test exhibits a sensitivity of 81% and a specificity ranging from 85 to 95%. [22] To arrive at the patient's post test likelihood of disease, the interpretation of the stress test result necessitates the integration of the patient's pretest likelihood with the test's sensitivity and specificity.
Myocardial perfusion imaging or scanning (also referred to as MPI or MPS) is a nuclear medicine procedure that illustrates the function of the heart muscle (). [1]It evaluates many heart conditions, such as coronary artery disease (CAD), [2] hypertrophic cardiomyopathy and heart wall motion abnormalities.
As the gamma camera images are acquired, the patient's heart beat is used to 'gate' the acquisition. The final result is a series of images of the heart (usually sixteen), one at each stage of the cardiac cycle. [citation needed] Depending on the objectives of the test, the doctor may decide to perform either a resting or a stress MUGA.
However, an exercise stress test is not always accurate in determining the presence of a blockage in the arteries. [11] Women and those who are young may show abnormalities on their test even though no signs of coronary ischemia or CAD are present. [29] Harmless arrhythmias present at baseline may distort the results. [11]
Coronary steal is also the mechanism in most drug-based cardiac stress tests; When a patient is incapable of doing physical activity they are given a vasodilator that produces a "cardiac steal syndrome" as a diagnostic procedure. The test result is positive if the patient's symptoms reappear or if ECG alterations are seen. [citation needed]
The resulting two sets of images are compared with each other to distinguish ischemic from infarcted areas of the myocardium. This imaging technique has a sensitivity of around 90%. [2] Resting images are useful only for detecting tissue damage, while stress images will also provide evidence of coronary artery (ischemia) disease. [3] [4]
The underlying principle is, under conditions of stress, diseased myocardium receives less blood flow than normal myocardium. MPI is one of several types of cardiac stress test. As a nuclear stress test, the average radiation exposure is 9.4 mSv, which when compared with a typical 2 view chest X-ray (.1 mSv) is equivalent to 94 Chest X-rays. [83]
A mnemonic can be used for some causes of ST depression, namely DEPRESSED ST: [citation needed]. D - Drooping valve (mitral valve prolapse) E - Enlargement of the left ventricle P - Potassium loss R - Reciprocal ST depression (e.g. inferior wall MI) E - Encephalon hemorrhage S - Subendocardial infarct S - Subendocardial ischemia E - Embolism (pulmonary) D - Dilated cardiomyopathy S - Shock T ...