Myocardial perfusion imaging is a noninvasive method for assessing the regional myocardial blood flow.
It depends on the introduction of a radioactive tracer and its uptake into the myocardial cells. Two types of tracer substance are used; Thalium-201 (a potassium analogue) and Technitium-99 based agent which is more advanced as regards improved imaging characteristics are used to assess myocardial perfusion and left ventricular performance in the same study.
Areas which are ischemic, have little blood flow and hence do not take up the tracer as well as normally perfused areas. This can be accentuated by exercise. Sometimes a drug (dipyridamole) is used to accentuate the ischemia and mimic the effect of exercise. Both exercise and resting views are compared to reveal areas showing reperfusion (ischemia) and areas showing fixed defects (infarcts). The involved arteries can be predicted.
- Cases with chest pain but without the classical picture when ischemic heart disease is suspected.
- Cases with acute myocardial infarction who have undergone thrombolysis to estimate the area salvaged.