肥大型心筋症における心筋脂肪酸代謝—病型における差異と左心室予備能に及ぼす影響

Myocardial Fatty Acid Metabolism in Patients with Hypertrophic Cardiomyopathy (HCM):The difference in this metabolism in two common types of HCM and its effect on left ventricular performance reserve

　目的：肥大型心筋症（HCM）のうち，非対称性中隔肥大（ASH）と心尖部肥大（APH）での心筋脂肪酸代謝の差異，HCMの心筋脂肪酸代謝と左心予備能の関連を検討した．方法：ASH 15例，APH 10例，健常（N）11例で，安静時に¹²³I-BMIPP（PP），²⁰¹Tl（Tl）心筋イメージングを行い，全身像，断層像をもとにglobalなPPの取り込み（UR），その洗い出し（％WO），局所的なPPの取り込み（PP／Tlマップ）を検討した．HCMを運動負荷心プールシンチより左室予備能良好群，不良群に区分した．結果：URはASH,APHでNより低下，％WOはASH,APHでNより亢進するも，ASHとAPHで差をみなかった．局所的なPPの取り込みの低下はAPHでは肥大部に限局していた．ASHでも取り込み低下は肥大部に存在したが，一部の症例では非肥大部にも及んでいた．左室予備能不良群では良好群に比しPPの欠損の広がりが有意に大であった．結論：ASH,APHで心筋脂肪酸代謝は本質的に異ならなかった．PPイメージングの定量評価はHCMの左室予備能判定に有用であった．

To study the difference in myocardial fatty acid metabolism in two common types of hypertrophic car-diomyopathy (HCM); asymmetrical septal hypertro-phy (ASH) and apical hypertrophy (APH), we have performed myocardial imaging with ¹²³I-BMIPP (BMIPP). Also we have studied the effect of myocar-dial fatty acid metabolism on left ventricular (LV) performance reserve in patients with HCM. Subjects of our study were 15 patients with ASH, 10 patients with APH and 11 normal subjects. Rest myocardial imaging with BMIPP (initial and delayed) and with ²⁰¹T1 (T1) were obtained. In addition to ordinary tomograms, whole-body imaging was performed to calculate myocardial accumulation of the isotope compared to total injected dose (%Uptake). As the indexes of global fatty acid metabolism, Uptake Ratio (%Uptake of BMIPP divided by %Uptake of T1) and %washout (%WO) (percent decrease of BMIPP between initial and delayed BMIPP images) were calculated. To quantitate regional BMIPP abnormality, a BMIPP/T1 map was constructed. The BMIPP/T1 Bull's-eye map represented the BMIPP uptake relative to myocardial perfusion in each pixel. The extent of regional abnor-mality was quantified as Defect Score. LV performance reserve was assessed in 17 patients with HCM by rest and exercise stress (Ex) ECG-gated cardiac blood pool imaging with ^99mTc.

Both in patients with ASH and APH. Uptake Ratio was significantly (p＜0.01) lower than that in normal subjects, but there was no difference between ASH and APH. %WO in ASH and APH was significantly greater than that in normal subjects, but no difference was observed between ASH and APH. In patients with APH, defect in the BMIPP/T1 map was localized to hypertrophic myocardium (apex and its vicinity), but in ASH, in some cases, defects were observed not only in the hypertrophic myocardium but also in the non-hypertrophied myocardium. According to LV ejection fraction (EF) response to Ex, HCM was divided into two groups (EF increased by Ex n=6, EF decreased by Ex n=11). In patients with EF decreased by Ex, Defect Score was significantly greater than that in patients with EF increased by Ex.

There was no fundamental difference between myocardial fatty acid metabolism in ASH and that in APH. Also, quantitative BMIPP imaging was useful to assess LV performance reserve in HCM.