HERSHEY – Nothing is scary about nuclear cardiology, except maybe the name. It is an essential part of the noninvasive evaluation of patients with chest pain. Diagnostic testing for the evaluation of chest pain can be divided into three categories: 1) functional, including exercise testing (e.g. treadmill); 2) physiologic, including stress echo and nuclear perfusion tests; and 3) anatomic, including noninvasive multi-detector computerized tomography and magnetic resonance imaging, as well as invasive cardiac catheterization.
Nuclear imaging of cardiac blood flow (perfusion) relies on detection of very low levels of gamma radiation emitted from the body following IV injection of a radioactive agent. The radiation is “seen” by a special camera using technology called SPECT, single photon emission computerized tomography. Imaging is performed twice – once following either exercise or medicine-induced stress and once at rest.
Patients sit or lie in a machine that essentially uses a two-headed digital gamma camera to detect the radioactivity coming from the heart. A computer then uses special software to construct three-dimensional images of the heart that can be reviewed in various sections as well as in motion to assess blood flow and function of the heart (ejection fraction). Images of the heart at rest and following stress are used to identify normal heart muscle (no significant blockages), obstructed blood flow with live heart muscle (myocardial ischemia), and obstructed blood flow with dead heart muscle (myocardial infarction or heart attack).
Why consider nuclear perfusion imaging? Since it is a direct reflection of both blood flow to the heart as well as the amount of live or damaged heart muscle, SPECT imaging studies give doctors a reliable assessment of both the blood supply to the heart as well as the motion of the heart muscle. These studies have an excellent correlation with prognosis. If a patient has a normal nuclear scan showing no blockage, the one-year prognosis for a cardiac event is less than 2 percent. That’s better than any other noninvasive test available for prognostic accuracy.
