Myocardial Perfusion Imaging

Myocardial Perfusion Imaging

Myocardial perfusion scan is a nuclear medicine procedure that illustrates the function of the heart muscle (myocardium).

It evaluates many heart conditions from coronary artery disease (CAD) to hypertrophic cardiomyopathy and myocardial wall motion abnormalities. The function of the myocardium is also evaluated by calculating the left ventricular ejection fraction (LVEF) of the heart. This scan is done in conjunction with a cardiac stress test. While a myocardial perfusion scan can determine with significant accuracy whether a patient has two or fewer coronary arteries which are dangerously occluded, the scan has a major fault in accuracy which is built into it which inevitably results in missed diagnoses of persons who suffer from three-vessel disease, the most serious form of coronary artery occlusion.

In layperson's terms, the problem is that nuclear cardiologists who read the results of nuclear scans have great difficult discerning the difference between a patient who has no coronary artery blockage in any of his arteries and a patient who has significant coronary artery occlusion in all of his major coronary arteries. Because the latter group has been found to constitute only 2.86% of all persons who undergo myocardial perfusion scanning, members of that group will inevitably be advised as if they are members of the group which has no coronary arterial occlusions and are thus advised that their results are negative. In other words, the patients who have the very most severe coronary artery disease will not learn that they are so afflicted unless other testing such as a CT angiography is performed or until a major life-threatening cardiac event takes place.

Planar techniques, such as conventional scintigraphy, are rarely used. Rather, SPECT is more common in the US. With multihead SPECT systems, imaging can often be completed in less than 10 minutes. With SPECT, interior and posterior abnormalities and small areas of infarction can be identified, as well as the occluded blood vessels and the mass of infarcted and viable myocardium.