Clinical Investigations: Imaging and Diagnostic Testing
Evaluation of β-blocker therapy in patients with dilated cardiomyopathy—Clinical meaning of iodine 123–metaiodobenzylguanidine myocardial single-photon emission computed tomography

https://doi.org/10.1067/mhj.2001.112783Get rights and content

Abstract

Background Patients with heart failure show signs of cardiac sympathetic dysfunction such as elevation of blood norepinephrine (NE) level, as a result of reduction in the number of sympathetic nerves, decrease in myocardial NE content, accelerated NE turnover or spillover of NE, and NE reuptake disorder at sympathetic nerve endings. In dilated cardiomyopathy (DCM), iodine 123–metaiodobenzylguanidine (MIBG) used clinically as a tracer for imaging of the sympathetic function was found to be useful in evaluation of severity and prognosis. Methods and Results A total of 143 123I-MIBG myocardial single-photon emission computed tomography (SPECT) images were taken at successive intervals on 58 patients with DCM (mean age 54 ± 11 years), as well as before and after therapy to determine the severity of DCM and the therapeutic effect of β-blocker. Patients were divided into group A (n = 20), in which left ventricular ejection fraction (LVEF) improved by 10% or more within 6 months after the administration of β-blocker, and group B (n = 20), in which there was less than a 10% change in LVEF. After 123I-MIBG myocardial SPECT was taken, the washout rate for the entire left ventricle was calculated from early and delayed images. The estimations of extent score and severity score were based on the polar map prepared from short axial images taken from 17 healthy volunteers (mean age 35 ± 5 years). There was a significant correlation between LVEF and 123I-MIBG findings (extent score, severity score, and washout rate) obtained before and after β-blocker therapy. After β-blocker therapy, LVEF and 123I-MIBG findings significantly improved in group A. On the other hand, no change occurred in 123I-MIBG findings in group B. There was no significant difference in LVEF between group A (32.1% ± 8.0%) and group B (29.5% ± 7.2%). Also, there was no significant difference in the washout rate between group A (54.4% ± 10.9%) and group B (52.9% ± 7.2%). Comparison of 123I-MIBG images before β-blocker therapy of group A and group B revealed that the extent score (26.5 ± 16.0 vs 44.5 ± 21.1, respectively; P <.01) and the severity score (24.9 ± 21.9 vs 58.2 ± 35.2, respectively; P <.01) on the basis of the early 123I-MIBG image was significantly lower for group A. Conclusions From the above findings, patients with DCM in which 123I-MIBG uptake is high on early images were expected to show improvement in cardiac function by β-blocker therapy. Findings also suggested that 123I-MIBG was useful for examining the severity of DCM, determining the applicability of β-blocker therapy, estimating the maintenance dosage of β-blocker, and evaluating prognosis. (Am Heart J 2001;141:645-52.)

Section snippets

Subjects

Subjects were 58 patients with DCM (51 male and 7 female, mean age 54 ± 11 years) whose diagnosis was confirmed by the handbook for diagnosis of the Japanese Ministry of Health and Welfare. Cardiac catheterization revealed no significant (50% or higher) coronary artery stenosis in any of the patients, and DCM was definitively diagnosed from myocardial biopsy specimens. The 58 cases complicated by acute heart failure were treated with digitalis, diuretics, or vasodilators. 123I-MIBG myocardial

Data acquisition by 123I-MIBG myocardial SPECT

With each patient resting, 111 MBq (3 mCi) of 123I-MIBG was intravenously administered, and 123I-MIBG myocardial SPECT images were obtained at 20 minutes (early image) and 4 hours (delayed image) after administration of 123I-MIBG. The images were taken by PRISM-3000 (Picker, Cleveland, Ohio/Shimadzu, Kyoto, Japan), a triple-head gamma camera equipped with a low-energy, general all-purpose collimator. Data were collected with a matrix size of 64 × 64 and a mode adjusted to step and sheet, 5

Comparison between LVEF and extent score/severity score of 123I-MIBG

There was a significant correlation between LVEF and extent score (r = –0.433, P <.001) or severity score (r = –0.405, P <.001) among the 143 early 123I-MIBG images (Figure 1).

. The relationship between LVEF and MIBG findings from the early image. There was a significant correlation between LVEF and extent score or severity score among the 143 early 123I-MIBG images.

A significant correlation was also found between LVEF and extent score (r = –0.503, P <.001) or severity score (r = –0.494, P <.001)

Discussion

It has been reported that β-blocker therapy improves cardiac function and exercise tolerance and at the same time lowers mortality rates in patients with chronic heart failure.4, 5, 6, 7, 8, 9 In cases of severe cardiac failure, however, β-blocker administration aggravates cardiac function. It is also not the case that β-blocker will be effective for all cases, and there are still no established criteria for dosage and duration of dosage.15 Clinical symptoms, LVEF, pulmonary arterial wedge

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    Reprint requests: Junichi Yamazaki, MD, First Department of Internal Medicine, Ohmori Hospital, Toho University School of Medicine, 6-11-1 Ohmori-Nishi, Ohta-ku, Tokyo, 143 Japan.

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