拡張型心筋症におけるβブロッカー療法の治療効果—123I-metaiodobenzylguanidine（MIBG）心筋SPECTの臨床的意義

Efficacy of β Blocker Therapy in Patients with Dilated Cardiomyopathy:Clinical meaning of 123I-metaiodobenzylguanidine (MIBG) myocardial SPECT

　拡張型心筋症（DCM）にMIBG心筋SPECTを施行し，βブロッカー療法による治療効果を経時的に観察した．対象（17例）をβブロッカー療法6カ月後までにLVEFが10％以上改善したA群と，10％未満の改善にとどまったB群に分類した．SPECT撮像後，左室全域のwashout rate（WR）を計測し，さらに健常者17例から作成したpolar mapを基準としてMIBGの欠損領域を示すextent score（ES）と欠損度を示すseverity score（SS）を算出した．A群では心機能の改善とともにWRも有意に改善したが，B群では両者とも不変であった．βブロッカー療法前のLVEFとMIBG所見をA群，B群で比較した．LVEFはA群，B群間で有意差は示されなかったが，A群においてMIBG初期像のESは33.3とB群の52.0と比較して有意な低値が示された（p＜0.05）．初期像でMIBGの取り込みが良好なDCMではβブロッカー薬による治療効果が期待された．また，MIBG心筋SPECTから算出したWRはDCMの治療効果を評価する上で有用であった．

We observed the efficacy of β-blocker therapy using MIBG myocardial SPECT for an average of 30.7 months in 17 patients (56±9yrs.) with dilated cardiomyopathy (DCM). Patients were divided into Group A with LVEF improved by 10% or more within 6 months after the administration of β-blocker,and Group B with less than 10% improvement in LVEF. After MIBG myocardial SPECT imagings, left ventricular washout rate was determined from early and delayed images, then, with a polar map composed on the basis of data from 17 healthy volunteers as the standard, the extent score and the severity score were calculated. In Group A, as the cardiac function improved, washout rate significantly normalized. In Group B, on the other hand, no change occurred in the cardiac function or washout rate. Com-parison of LVEF and MIBG images before β-blocker therapy between Group A and B revealed that the extent score in early MIBG images was significantly lower for Group A (33.3±12.6 vs 52.0±13.9;p＜0.05). In patients with DCM, in whom the MIBG uptake is high in early imagings, improvement in cardiac function can be expected by the use of β-blocker therapy. MIBG washout rate was useful in evaluation of the severity of DCM, and in observation of the results of β-blocker therapy in patients with DCM.