99mTc-MIBI (RP-30) to define the extent of myocardial Ischemia and evaluate ventricular function

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Abstract
99mTc-MIBI, a new myocardial perfusion agent, is a technetium labeled isonitrile derivative. We have taken advantage of the physical characteristics of99mTc to combine at rest, post infarction, ventricular function studies with analysis of perfusion. We have studied at rest and at stress, 22 patients with coronary artery disease selected on the basis of an abnormal coronary angiogram or on the basis of a positive exercise ECG stress test for symptomatic angina. We have also studied, at rest only, 20 patients with a previous myocardial infarction. A comparative thallium planar scintigraphy was obtained for all patients. The sensitivity of99mTc-MIBI scintigraphy for detecting individual vessel lesions at stress was 88% as compared with 83% for201TI. Sensitivity was higher in patients with previous myocardial infarction (93% for the 2 isotopes) than in patients without (85% for99mTc-MIBI versus 81% for201TI). Segmental myocardial correspondence between99mTc-MIBI and201Tl was very close (92%). The overall sensitivity for the detection of acute myocardial infarction reached respectively 91% for99mTc MIBI and 87% for201T1. The specificity in the regions corresponding to arteries not involved was excellent for both tracers as we did not observe any false positive result. This is important information but it does not correspond to the specificity to detect coronary artery disease in the overall patient population. The correlation between first pass left ventricular ejection fraction obtained with99mTc-MIBI and equilibrium left ventricular ejection fraction obtained with99mTc red cells was excellent (r = 0.96). It was not as good but was still satisfactory for the right ventricle (r=0.75). By comparison of diastolic and systolic frames., gated tomography provides analysis of regional wall motion and wall thickening. In this preliminary study, we have only limited data collected from a selected population with a high prevalence of coronary artery disease and myocardial infarction. Thus, no definitive conclusion can be drawn on the sensitivity and specificity of these tests when performed in the general population. Further studies analyzing comparatively MIBI scintigrams and angiographic results in a large number appears to be a very promising perfusion agent to document myocardial infarction and myocardial ischemia as well as to provide functional information on global and regional ventricular function.

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