Assessment of the myocardial sympathetic nerve abnormalities in patients with ischemic heart disease

The usefulness of myocardial scintigraphy with meta-iodobenzylguanidine (MIBG) was examined in the assessment of myocardial sympathetic nerve abnormalities. The subjects were 14 patients with ischemic heart disease associated with chest pain. All patients underwent early and delayed imaging after iv injection of I-123 MIBG at rest. In addition, 10 of the 14 patients also had exercise Tl myocardial single photon emission computed tomography (SPECT) and the other four patients with unstable angina had Tl myocardial SPECT at rest. Left ventricle was divided into 7 segments, and tracer uptake was visually classified into 4 degrees. Washout rate was calculated on myocardial MIBG SPECT images. Exercise SEPCT images showed ischemia in 18 (38 zones) of 21 segments with significant coronary artery disease. Myocardial MIBG imaging showed a decreased tracer uptake in 19 (36 zones) of 21 segments on early images and in all 21 segments (42 zones) on delayed images. Myocardial Tl imaging at rest showed a decreased tracer uptake in 3 (4 zones) of 5 segments (significantly stenosed lesions, except for infarcted ones). All of the 5 segments had a decreased tracer uptake on both early and delayed MIBG images. Washout rates significantly differed in normal myocardium (25±8%), ischemic zones (40±21%) and infarcted zones (69±26%). These results indicated that myocardial sympathetic nerve abnormalities can be induced not only by infarction but also by repeated myocardial ischemia. Because MIBG imaging at rest had a high sensitivity in the detection of myocardial ischemia, it appeared to be useful especially in patients with acute myocardial infarction unable to exercise and those with unstable angina. The combination of washout rate may provide a more additional information on myocardial viability. (N.K.)