正常冠動脈を有する完全左脚ブロック3症例の心筋シンチ所見

Unique Features of Cardiac Imaging in 3 Patients with Complete Left Bundle Branch Block

　正常冠動脈を有する完全左脚ブロック3症例に，運動負荷²⁰¹Tlシンチ（Tl），¹²³I-MIBGシンチ（MIBG），¹²³I-BMIPPシンチ（BMIPP）を施行した．症例1はsmall coronary　artery disease，症例2は拡張型心筋症，症例3は明らかな心疾患のない症例である．左室駆出率は，各々49％，30％，68％であった．Tlは，全症例で前壁中隔の再分布を示した．BMIPPは，症例1と2は前壁中隔の逆再分布を示し，症例3は前壁中隔の持続性集積低下を呈した．MIBGは，症例1は著明なwashoutの亢進により遅延像の不明瞭化，症例2はwashoutの軽度の亢進により，遅延像で下礎領域の集積低下，症例3は正常像を呈した．正常冠動脈を有する完全左脚ブロック症例では，TlはCLBBBに特有の変化を示し，BMIPPはCLBBBの前壁中隔の脂肪酸代謝異常を，MIBGのwashoutの変化は原疾患の病態を反映する可能性が示唆された．

We encountered 3 cases with complete left bundle branch block (CLBBB) and normal coronary angio-gram (case 1 with small-coronary-artery disease, case 2 with dilated cardiomyopathy, and case 3 without organic heart disease), who underwent exercise ²⁰¹Tl imaging (Tl), ¹²³I-BMIPP imaging (BMIPP), and ¹²³I-MIBG imaging (MIBG). Left ventricular ejection frac-tion was 49% in case 1, 30% in case 2, and 68% in case 3. All cases had a redistribution in the anteroseptal wall on Tl. However, ¹²³I-BMIPP uptake in the anteroseptal wall showed a reverse redistribution in cases 1 and 2, and a persistent hypoperfusion in case 3. On MIBG, case 1 had a markedly enhanced washout of ¹²³I-MIBG. Thus, patients with CLBBB had various abnormalities of cardiac imaging. Although the mechanisms of abnor-mal uptake and its relation to heart disease remain unknown, it appears that an enhanced ¹²³I-MIBG clear-ance may be characteristic of CLBBB patients with small-coronary-artery disease.