QUANTITATIVE-ANALYSIS OF I-123 METAIODOBENZYLGUANIDINE (METAIODOBENZYLGUANIDINE) UPTAKE IN HYPERTROPHIC CARDIOMYOPATHY

Myocardial scintigraphy with 123I-meta-iodobenzylguanidine (MIBG) and thallium-201 (201TI) was performed in 29 patients with hypertrophic cardiomyopathy (HCM) using whole-body scintigraphy and single-photon emission computed tomography (SPECT). Nonhypertensive patients were classified into three groups according to the septal thickness determined by ultrasonography; group 1 (wall thickness<16 mm, n=5), group 2 (from 16 to 20 mm, n=12) and group 3 (>20 mm, n=4). The regional myocardial uptakes of both 201TI and 123I-MIBG (percent of injected dose/cm3 myocardium) were higher in the more hypertrophic septa. However, when regional MIBG uptake at 3 hours was divided by the 201TI uptake to calculate the MIBG uptake per unit of blood flow, the hypertrophic septa showed lower mean values-0.39±0.23 and 0.50±0.10 in groups 3 and 2, respectively (p<0.1 compared with 0.69±0.20 in group 1). The regional MIBG clearance rate in the septum was significantly higher in group 3 compared with group 1 (13.4±8.0%/hr versus 1.5±6.2%/hr, p<0.05). The uptake and 123I-MIBG clearance rate in the lateral wall showed a similar tendency. Myocardial uptake determined by whole-body scintigraphy was slightly increased in group 2 (3.5±0.6%, p<0.05) compared with group 1 (2.7±0.8%); however, it was lower in group 3 (2.7±0.4%). Myocardial 123I-MIBG distribution demonstrated various patterns in comparison with 201TI distribution, suggesting that flow-independent changes in sympathetic innervation or activity may exist in patients with HCM. 123I-MIBG clearance from the myocardium, myocardial uptake, and a comparison with the 201TI study seemed to be useful in the evaluation of the severity of myocardial hypertrophy in HCM. © 1990.