I-123-MIBG myocardial scintigraphy as a noninvasive screen for the diagnosis of coronary artery spasm

Background. It has been suggested that the sympathetic nervous system might play an important role in the development of coronary artery spasm. Howeve r, no cardiac imaging modality has been able to demonstrate abnormal sympat hetic innervation in patients with coronary artery spasm. The purpose of th is study was to assess the presence and location of abnormal sympathetic in nervation using iodine 123-metaiodobenzylguanidine (I-123-MIBG) single phot on emission computed tomography (SPECT) and to evaluate the clinical effica cy of I-123-MIBG SPECT as a noninvasive screening test in patients with cor onary artery spasm. Methods and Results, Coronary arteriography and a provocative test with int ravenous administration of ergonovine maleate were performed in 26 patients (20 men, 6 women, mean age 48.2 +/- 12.0 years, range 20 to 67 years) who were suspected of having a coronary artery spasm. The subjects were divided into 2 groups: group 1 (n = 18) comprised subjects with a positive provoca tive test result, and group 2 (n = 8) comprised subjects with negative prov ocative test results. Ten healthy subjects served as controls. No abnormal MIBG uptake was observed in the control subjects. Abnormal sympathetic nerv ous innervation using 123I-MIBG SPECT was observed either as a reduced upta ke or a defective pattern in the perfused areas in 13 of the 18 regions sup plied by vessels of ergonovine-induced vasospasm, Normal sympathetic innerv ation, as evidenced by normal I-123-MIBG uptake, was noted in all of the 60 segments of normal vessel territories. Reduced uptake of I-123-MIBG was no t detected in the perfused areas of 5 vasospasm-induced vessels (perfusion territory of left anterior descending coronary artery [LAD] and the right c oronary artery [RCA] in 2 and 3 patients, respectively). The sensitivity an d specificity of I-123-MIBG for detection of coronary artery spasm were 72. 2% (95% confidence interval [CI] 55% to 89%) and 100%, respectively. The po sitive predictive and negative predictive values were 100% and 92.3% (95% C I 91% to 93%), respectively, Conclusion. I-123-MIBG SPECT is a feasible method to evaluate noninvasively and localize the territories of coronary arteries with spasm. Invasive dia gnostic coronary arteriography with ergonovine provocation test may be unne cessary for diagnosis of coronary artery spasm in patients with typical res ting pain, negative exercise test or normal thallium perfusion scan results , but showing abnormalities in I-123-MIBG SPECT.