Dual Energy CT Scan
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A Nuclear Medicine (NM) cardiac stress test involves a scintigraphic (radioactive isotope) scan of the heart in conjunction with an exercise stress test to evaluate myocardial perfusion. The stress test usually uses treadmill exercise, but when the patient is unable to exercise then “stress” can be pharmacologically induced (intravenous dipyridamole (Persantin), adenosine or dobutamine).
Scanning is carried out at rest and also after cardiac stressing. Normal muscle takes up isotope, but non-viable cardiac muscle does not. In ischaemic cardiac muscle, uptake is reduced during stress, but is present at rest.
NM cardiac stress tests have been shown to have a higher accuracy in the detection of clinically significant coronary artery disease when compared to ECG stress tests alone. They have a proven value in predicting the risk of myocardial infarction.
NM cardiac stress testing can be used for:
There are no prerequisites for this study.
Known allergy to any of the pharmacological stress agents (dipyridamole (Persantin), adenosine or dobutamine). More specific contraindications for dipyridamole and adenosine include:
Caution is exercised when using dobutamine in patients with suspected tendency to ventricular tachyarrhythmias and in patients with atrial tachyarrhythmias (particularly if not on anticoagulation).
As the study relies on isotope radioactivity, it might not be suitable for pregnant women. The benefit versus risk from the small amount of radiation should be discussed with the NM specialist.
See InsideRadiology: Nuclear Medicine for further information about the precautions to take with NM studies for breast-feeding patients and those in close contact with children.
Claustrophobic and obese patients, whose weight exceeds the limits of the imaging bed, can be scanned with the patient sitting up and two-dimensional (planar instead of tomographic) images acquired.
Minor allergies to the pharmacological stress agents might be relative contraindications.
The likelihood of an adverse reaction to the radiopharmaceutical is very remote, in the order of 1 in 10,000. The likelihood of a serious allergic event is even less likely. The adverse effects of the pharmacological stress agents are outlined above.
There is no post-procedural care required in an uncomplicated study. Women who are breast-feeding and people who are the primary or sole carer of small children might need to make special preparations after the test. Direct breast-feeding and close contact with young children should be avoided for 4 hours after the test. See advice given in InsideRadiology: Nuclear Medicine.
The alternatives to NM cardiac stress tests in the assessment of myocardial perfusion are:
Colquhoun D. CSANZ Position Statement: Clinical Exercise Stress Testing in Adults. 2014 Aug. Available from: http://www.csanz.edu.au/wp-content/uploads/2014/08/Clinical_Exercise_Stress_Testing_2014-August.pdf
Page last modified on 24/8/2018.
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