Whilst the CTCA scan and coronary angiogram give anatomical information about the coronary arteries and any possible narrowing, Myocardial Perfusion Scanning (MPS, Myoview, Thallium scan) looks at the functional uptake of blood by the heart muscle and by implication the coronary blood supply to the heart. This is achieved by exercising the heart either with physical exercise (eg treadmill or exercise bike) or in some situations by using a drug infusion to increase the heart rate.
In Myocardial Perfusion Scans a small dose of a radioisotope is injected into a vein and images of the heart are observed using a special scanner (gamma camera) following exercise ‘stress’ and at rest. The basic principle of the test is to look at whether tracer uptake is reduced in the stress image which can suggest limitation in blood supply to the heart and the possible need for further tests. A further useful function of myocardial perfusion scanning is in planning for operations since it is a non-invasive way of assessing the potential cardiac risk of non-cardiac surgery.
All test results should be treated with caution and interpreted in the context of a clinical assessment.