1995 Volume 44 Issue 9 Pages 616-626
To study myocardial norepinephrine (NE) activity in essential hypertension (HT) and especially to clarify the effect of left ventricular (LV) hypertrophy and LV performance reserve upon it, we performed myocardial imaging with 123I-metaiodobenzylguanidine (123I-MIBG) and 201Tl at rest in 23 patients with HT and 10 normal subjects. In addition to ordinary tomograms, we obtained whole body images with 123I-MIBG and 201Tl to calculate the ratio of myocardial accumulation of each radionuclide to total injected dose (%Uptake) . As the index of myocardial 123I-MIBG uptake, we calculated Uptake Ratio (%Uptake of 123I-MIBG in delayed image divided by %Uptake of 201Tl) . Reduction of myocardial 123I-MIBG during 3h (WOR) was also calculated. From the Bull's-eye map, the extent of defect was quantitatively assessed as Defect Score.
To study the effect of LV hypertrophy upon NE kinetics, patients with HT were divided into 2 groups according to the LV mass (LVM) which was calculated by echocardiography. In Group I (LVM>130g/m2, n=16), Uptake Ratio was lower than that in Group II (LVM<130g/m2, n=7) and WOR was accererated in Group I than in Group II. Uptake Ratio and WOR were identical between Group II and normal subjects. The incidence of 123I-MIBG defect and Defect Score were significantly greater in Groupl (incidence: 94%, Defect Score: 3.0±1.3) than in GroupII (incidence: 43%, Defect Score: 1.1±0.6) . In order to study the effect of LV performance reserve, patients with HT were divided into two groups according to LV ejection fraction (EF) responses to exercise stress (Ex) which were obtained by 99mTc blood pool imaging. In 13 patients LVEF increased by Ex (Group A) and in 7 patients LVEF decreased or did not change by Ex (Group B) . In Group B, Uptake Ratio was significantly smaller than in Group A and normal subject, and WOR was significantly accelerated comparing with those in Group A and normal subjects. The incidence of 123I-MIBG defect and Defect Score were greater in Group B than that in Group A but they were not statistically significant. These two factors (LVM and LVEF response) seemed to influence upon myocardial NE kinetics independently. These results suggested that LVM and LV performance reserve influenced upon myocardial NE kinetics in patients with HT and quantitative analysis of 123I-MIBG imaging may be helpful for assessing the prognosis of HT.
