Myocardial perfusion imaging and stress testing

An injection of chemicals that are taken up by the heart muscleTissue made up of cells that can contract to bring about movement. can show up on scans to enable doctors to detect areas of heart muscleTissue made up of cells that can contract to bring about movement. that do not have a good bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. supply, caused, for example, by a heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction..

Such chemicals are called 'radiotracersSubstances labelled with a radioisotope that may be used in some imaging investigations.' and this imaging technique is called nuclear myocardial perfusion imagingImaging of the heart after intravenous injection of a radioactive tracer, to assess the blood supply to the heart itself. (MPI). Research has shown that this test is safe and reliable.[1,2]

As a variation of this test, a drug can be given that dilates the arteries of the heart and puts the heart under stressRelating to injury or concern., so simulating what happens when someone undertakes exercise. Once the drug takes effect, the scans can show how good the bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. supply is to the muscleTissue made up of cells that can contract to bring about movement. of the heart under stressful conditions.

Often, this test is given to people who are unable to have an exercise ECG because they cannot exercise - for example, owing to arthritisInflammation of one or more joints of the body. or another medical condition.[2]

Stress echocardiographyThe use of ultrasound to examine the heart as it is pumping. is widely used for the diagnosisThe process of determining which condition a patient may have. of coronaryRelating to the arteries supplying the heart itself. arteryA blood vessel that carries blood away from the heart. Apart from the pulmonary artery and umbilical artery, all arteries carry oxygenated blood. disease. It is an alternative to myocardial perfusion scanning, and has a similar level of accuracy. As described above, echocardiographyThe use of ultrasound to examine the heart as it is pumping. is a specialized type of imaging that can show how well the heart muscleTissue made up of cells that can contract to bring about movement. is contracting. Putting the heart under stressRelating to injury or concern., either with exercise or with medications, allows doctors to identify which areas of the heart are lacking in oxygen by observing how the heart is pumping.[3,4]

References: 
  1. Improving the early diagnosisThe process of determining which condition a patient may have. of acuteHas a sudden onset. myocardial infarctionDeath of an area of heart muscle due to poor blood supply.. Banerjee A. Postgrad Med J 1996;72:705-8.
  2. Myocardial perfusion imaging: a validated and mature cardiac imaging modality. Australian Family Physician 2006;35:288-92.
  3. Boon NA, Colledge NR and Walker BR. Davidson's Principles and Practice of Medicine. Churchill Livingstone Elsevier. 2006; 20th edition.
  4. The diagnostic accuracy of pharmacological stressRelating to injury or concern. echocardiographyThe use of ultrasound to examine the heart as it is pumping. for the assessment of coronaryRelating to the arteries supplying the heart itself. arteryA blood vessel that carries blood away from the heart. Apart from the pulmonary artery and umbilical artery, all arteries carry oxygenated blood. disease: a meta-analysis. Picano E, Molinaro S and Pasanisi E. Cardiovascular Ultrasound 2008;6:30.