It has been suggested that the sympathetic nervous system might play an important role in the development of coronary artery spasm. Recently, advances have made possible the imaging of the cardiac adrenergic nervous system with metaiodobenzylguanidine (MIBG) labeled with iodine-123. The purpose of this study was to assess the presence and location of abnormal sympathetic innervation by iodine-123-metaiodobenzylguanidine single-photon emission computed tomography (SPECT) and to evaluate the clinical efficacy of iodine-123-MIBG SPECT as a noninvasive screening test in patients with coronary artery spasm.

Coronary arteriography and provocative test with intravenous administration of ergonovine maleate were performed in 26 patients (21 men, 5 women, mean age 49.1±9.3, range: 26-59) who were suspected of having a coronary artery spasm. The subjects were divided into 2 groups ; Group 1 comparised of 18 patients subjects to the positive provocative test, Group 2 comparised of 8 patients subjects to the negative provocative test. Four healthy subjects served as control. All patients also underwent iodine-123-MIBG SPECT for the evaluation of cardiac sympathetic integrity. The SPECT findings were qualitatively evaluated by two experienced physicians who were blind to the clinical data.

Abnormal sympathetic nervous innervation using iodine-123-MIBG SPECT was observed either as a reduced uptake or defect pattern in the perfused areas in 13 of the 18 vessels of ergonovine induced vasospasm. Normal sympathetic innervation as evidenced by normal iodine-123-MIBG uptake was noted in all of the 60 segments of normal vessel territories. Reduced uptake of iodine-123-MIBG was not detected in the perfused areas of five vasospasm-induced vessels (perfusion territory of LAD in 2 and the RCA in 3 patients). The sensitivity and specificity of iodine-123-MIBG for detection coronary artery spasm were 72.2% (95% confidence interval [CI] 55% to 89%) and 100%, respectively. The positive predictive value and negative predictive value were 100% and 92.3% (95% CI 91% to 93%), respectively.

Iodine-123-MIBG SPECT is a feasible method to noninvasively evaluate and localize the territories of coronary arteries with spasms. Invasive diagnostic coronary arteriography with ergonovine provocation test may be unnecessary for the diagnosis of coronary artery spasm in patients with typical resting pain, negative exercise test or normal thallium perfusion scan, but abnormal iodine-123-MIBG SPECT.