[Myocardial sympathetic activity and characteristics in hypertrophic cardiomyopathy: comparison with hypertensive...

The characteristics of myocardial sympathetic activity were studied using myocardial imaging with I-123-metaiodobenzylguanidine (MIBG) in 16 patients with hypertrophic cardiomyopathy (HCM), 12 patients with essential hypertension and left ventricular hypertrophy (HT) and 10 normal subjects. Myocardial imaging with MIBG and thallium-201 (T1) was performed at rest on a separate day. The index of myocardial MIBG uptake, "uptake ratio", was calculated from the percentage uptake of MIBG and T1. Reduction of myocardial MIBG during 3 hours (percentage washout) was also calculated. The extent of the defect was quantitatively assessed (defect score) from the bull's eye map. Global "uptake ratio" of the delayed image decreased in the order of normal subjects, patients with HT and those with HCM (p < 0.01). Defects in MIBG images were observed in all patients with HCM and 92% in those with HT. The defects were located in the inferior and lateral segments in patients with HT, but around the entire left ventricle in patients with HCM. Both groups had smaller regional "uptake ratio" than normal subjects, but HT and HCM demonstrated different behaviors: reduced in the inferior and lateral segments as compared with other segments in HT, but distributed equally in all segments in HCM. In patients with HCM, percentage washout was significantly accelerated in comparison with patients with HT and normal subjects in both global and regional analyses, but there was no difference between the latter two groups. Disturbance of myocardial sympathetic activity observed in patients with HCM by MIBG uptake and washout differed from that caused by HT.